1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488 4489 4490 4491 4492 4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685 4686 4687 4688 4689 4690 4691 4692 4693 4694 4695 4696 4697 4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715 4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730 4731 4732 4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788 4789 4790 4791 4792 4793 4794 4795 4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828 4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840 4841 4842 4843 4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856 4857 4858 4859 4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 4898 4899 4900 4901 4902 4903 4904 4905 4906 4907 4908 4909 4910 4911 4912 4913 4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988 4989 4990 4991 4992 4993 4994 4995 4996 4997 4998 4999 5000 5001 5002 5003 5004 5005 5006 5007 5008 5009 5010 5011 5012 5013 5014 5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025 5026 5027 5028 5029 5030 5031 5032 5033 5034 5035 5036 5037 5038 5039 5040 5041 5042 5043 5044 5045 5046 5047 5048 5049 5050 5051 5052 5053 5054 5055 5056 5057 5058 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289 5290 5291 5292 5293 5294 5295 5296 5297 5298 5299 5300 5301 5302 5303 5304 5305 5306 5307 5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339 5340 5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419 5420 5421 5422 5423 5424 5425 5426 5427 5428 5429 5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472 5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552 5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575 5576 5577 5578 5579 5580 5581 5582 5583 5584 5585 5586 5587 5588 5589 5590 5591 5592 5593 5594 5595 5596 5597 5598 5599 5600 5601 5602 5603 5604 5605 5606 5607 5608 5609 5610 5611 5612 5613 5614 5615 5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626 5627 5628 5629 5630 5631 5632 5633 5634 5635 5636 5637 5638 5639 5640 5641 5642 5643 5644 5645 5646 5647 5648 5649 5650 5651 5652 5653 5654 5655 5656 5657 5658 5659 5660 5661 5662 5663 5664 5665 5666 5667 5668 5669 5670 5671 5672 5673 5674 5675 5676 5677 5678 5679 5680 5681 5682 5683 5684 5685 5686 5687 5688 5689 5690 5691 5692 5693 5694 5695 5696 5697 5698 5699 5700 5701 5702 5703 5704 5705 5706 5707 5708 5709 5710 5711 5712 5713 5714 5715 5716 5717 5718 5719 5720 5721 5722 5723 5724 5725 5726 5727 5728 5729 5730 5731 5732 5733 5734 5735 5736 5737 5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765 5766 5767 5768 5769 5770 5771 5772 5773 5774 5775 5776 5777 5778 5779 5780 5781 5782 5783 5784 5785 5786 5787 5788 5789 5790 5791 5792 5793 5794 5795 5796 5797 5798 5799 5800 5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817 5818 5819 5820 5821 5822 5823 5824 5825 5826 5827 5828 5829 5830 5831 5832 5833 5834 5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851 5852 5853 5854 5855 5856 5857 5858 5859 5860 5861 5862 5863 5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892 5893 5894 5895 5896 5897 5898 5899 5900 5901 5902 5903 5904 5905 5906 5907 5908 5909 5910 5911 5912 5913 5914 5915 5916 5917 5918 5919 5920 5921 5922 5923 5924 5925 5926 5927 5928 5929 5930 5931 5932 5933 5934 5935 5936 5937 5938 5939 5940 5941 5942 5943 5944 5945 5946 5947 5948 5949 5950 5951 5952 5953 5954 5955 5956 5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977 5978 5979 5980 5981 5982 5983 5984 5985 5986 5987 5988 5989 5990 5991 5992 5993 5994 5995 5996 5997 5998 5999 6000 6001 6002 6003 6004 6005 6006 6007 6008 6009 6010 6011 6012 6013 6014 6015 6016 6017 6018 6019 6020 6021 6022 6023 6024 6025 6026 6027 6028 6029 6030 6031 6032 6033 6034 6035 6036 6037 6038 6039 6040 6041 6042 6043 6044 6045 6046 6047 6048 6049 6050 6051 6052 6053 6054 6055 6056 6057 6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083 6084 6085 6086 6087 6088 6089 6090 6091 6092 6093 6094 6095 6096 6097 6098 6099 6100 6101 6102 6103 6104 6105 6106 6107 6108 6109 6110 6111 6112 6113 6114 6115 6116 6117 6118 6119 6120 6121 6122 6123 6124 6125 6126 6127 6128 6129 6130 6131 6132 6133 6134 6135 6136 6137 6138 6139 6140 6141 6142 6143 6144 6145 6146 6147 6148 6149 6150 6151 6152 6153 6154 6155 6156 6157 6158 6159 6160 6161 6162 6163 6164 6165 6166 6167 6168 6169 6170 6171 6172 6173 6174 6175 6176 6177 6178 6179 6180 6181 6182 6183 6184 6185 6186 6187 6188 6189 6190 6191 6192 6193 6194 6195 6196 6197 6198 6199 6200 6201 6202 6203 6204 6205 6206 6207 6208 6209 6210 6211 6212 6213 6214 6215 6216 6217 6218 6219 6220 6221 6222 6223 6224 6225 6226 6227 6228 6229 6230 6231 6232 6233 6234 6235 6236 6237 6238 6239 6240 6241 6242 6243 6244 6245 6246 6247 6248 6249 6250 6251 6252 6253 6254 6255 6256 6257 6258 6259 6260 6261 6262 6263 6264 6265 6266 6267 6268 6269 6270 6271 6272 6273 6274 6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286 6287 6288 6289 6290 6291 6292 6293 6294 6295 6296 6297 6298 6299 6300 6301 6302 6303 6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315 6316 6317 6318 6319 6320 6321 6322 6323 6324 6325 6326 6327 6328 6329 6330 6331 6332 6333 6334 6335 6336 6337 6338 6339 6340 6341 6342 6343 6344 6345 6346 6347 6348 6349 6350 6351 6352 6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364 6365 6366 6367 6368 6369 6370 6371 6372 6373 6374 6375 6376 6377 6378 6379 6380 6381 6382 6383 6384 6385 6386 6387 6388 6389 6390 6391 6392 6393 6394 6395 6396 6397 6398 6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412 6413 6414 6415 6416 6417 6418 6419 6420 6421 6422 6423 6424 6425 6426 6427 6428 6429 6430 6431 6432 6433 6434 6435 6436 6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447 6448 6449 6450 6451 6452 6453 6454 6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465 6466 6467 6468 6469 6470 6471 6472 6473 6474 6475 6476 6477 6478 6479 6480 6481 6482 6483 6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516 6517 6518 6519 6520 6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533 6534 6535 6536 6537 6538 6539 6540 6541 6542 6543 6544 6545 6546 6547 6548 6549 6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567 6568 6569 6570 6571 6572 6573 6574 6575 6576 6577 6578 6579 6580 6581 6582 6583 6584 6585 6586 6587 6588 6589 6590 6591 6592 6593 6594 6595 6596 6597 6598 6599 6600 6601 6602 6603 6604 6605 6606 6607 6608 6609 6610 6611 6612 6613 6614 6615 6616 6617 6618 6619 6620 6621 6622 6623 6624 6625 6626 6627 6628 6629 6630 6631 6632 6633 6634 6635 6636 6637 6638 6639 6640 6641 6642 6643 6644 6645 6646 6647 6648 6649 6650 6651 6652 6653 6654 6655 6656 6657 6658 6659 6660 6661 6662 6663 6664 6665 6666 6667 6668 6669 6670 6671 6672 6673 6674 6675 6676 6677 6678 6679 6680 6681 6682 6683 6684 6685 6686 6687 6688 6689 6690 6691 6692 6693 6694 6695 6696 6697 6698 6699 6700 6701 6702 6703 6704 6705 6706 6707 6708 6709 6710 6711 6712 6713 6714 6715 6716 6717 6718 6719 6720 6721 6722 6723 6724 6725 6726 6727 6728 6729 6730 6731 6732 6733 6734 6735 6736 6737 6738 6739 6740 6741 6742 6743 6744 6745 6746 6747 6748 6749 6750 6751 6752 6753 6754 6755 6756 6757 6758 6759 6760 6761 6762 6763 6764 6765 6766 6767 6768 6769 6770 6771 6772 6773 6774 6775 6776 6777 6778 6779 6780 6781 6782 6783 6784 6785 6786 6787 6788 6789 6790 6791 6792 6793 6794 6795 6796 6797 6798 6799 6800 6801 6802 6803 6804 6805 6806 6807 6808 6809 6810 6811 6812 6813 6814 6815 6816 6817 6818 6819 6820 6821 6822 6823 6824 6825 6826 6827 6828 6829 6830 6831 6832 6833 6834 6835 6836 6837 6838 6839 6840 6841 6842 6843 6844 6845 6846 6847 6848 6849 6850 6851 6852 6853 6854 6855 6856 6857 6858 6859 6860 6861 6862 6863 6864 6865 6866 6867 6868 6869 6870 6871 6872 6873 6874 6875 6876 6877 6878 6879 6880 6881 6882 6883 6884 6885 6886 6887 6888 6889 6890 6891 6892 6893 6894 6895 6896 6897 6898 6899 6900 6901 6902 6903 6904 6905 6906 6907 6908 6909 6910 6911 6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922 6923 6924 6925 6926 6927 6928 6929 6930 6931 6932 6933 6934 6935 6936 6937 6938 6939 6940 6941 6942 6943 6944 6945 6946 6947 6948 6949 6950 6951 6952 6953 6954 6955 6956 6957 6958 6959 6960 6961 6962 6963 6964 6965 6966 6967 6968 6969 6970 6971 6972 6973 6974 6975 6976 6977 6978 6979 6980 6981 6982 6983 6984 6985 6986 6987 6988 6989 6990 6991 6992 6993 6994 6995 6996 6997 6998 6999 7000 7001 7002 7003 7004 7005 7006 7007 7008 7009 7010 7011 7012 7013 7014 7015 7016 7017 7018 7019 7020 7021 7022 7023 7024 7025 7026 7027 7028 7029 7030 7031 7032 7033 7034 7035 7036 7037 7038 7039 7040 7041 7042 7043 7044 7045 7046 7047 7048 7049 7050 7051 7052 7053 7054 7055 7056 7057 7058 7059 7060 7061 7062 7063 7064 7065 7066 7067 7068 7069 7070 7071 7072 7073 7074 7075 7076 7077 7078 7079 7080 7081 7082 7083 7084 7085 7086 7087 7088 7089 7090 7091 7092 7093 7094 7095 7096 7097 7098 7099 7100 7101 7102 7103 7104 7105 7106 7107 7108 7109 7110 7111 7112 7113 7114 7115 7116 7117 7118 7119 7120 7121 7122 7123 7124 7125 7126 7127 7128 7129 7130 7131 7132 7133 7134 7135 7136 7137 7138 7139 7140 7141 7142 7143 7144 7145 7146 7147 7148 7149 7150 7151 7152 7153 7154 7155 7156 7157 7158 7159 7160 7161 7162 7163 7164 7165 7166 7167 7168 7169 7170 7171 7172 7173 7174 7175 7176 7177 7178 7179 7180 7181 7182 7183 7184 7185 7186 7187 7188 7189 7190 7191 7192 7193 7194 7195 7196 7197 7198 7199 7200 7201 7202 7203 7204 7205 7206 7207 7208 7209 7210 7211 7212 7213 7214 7215 7216 7217 7218 7219 7220 7221 7222 7223 7224 7225 7226 7227
|
Network Working Group R. Housley
Request for Comments: 3280 RSA Laboratories
Obsoletes: 2459 W. Polk
Category: Standards Track NIST
W. Ford
VeriSign
D. Solo
Citigroup
April 2002
Internet X.509 Public Key Infrastructure
Certificate and Certificate Revocation List (CRL) Profile
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This memo profiles the X.509 v3 certificate and X.509 v2 Certificate
Revocation List (CRL) for use in the Internet. An overview of this
approach and model are provided as an introduction. The X.509 v3
certificate format is described in detail, with additional
information regarding the format and semantics of Internet name
forms. Standard certificate extensions are described and two
Internet-specific extensions are defined. A set of required
certificate extensions is specified. The X.509 v2 CRL format is
described in detail, and required extensions are defined. An
algorithm for X.509 certification path validation is described. An
ASN.1 module and examples are provided in the appendices.
Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . 4
2 Requirements and Assumptions . . . . . . . . . . . . . . 5
2.1 Communication and Topology . . . . . . . . . . . . . . 6
2.2 Acceptability Criteria . . . . . . . . . . . . . . . . 6
2.3 User Expectations . . . . . . . . . . . . . . . . . . . 7
2.4 Administrator Expectations . . . . . . . . . . . . . . 7
3 Overview of Approach . . . . . . . . . . . . . . . . . . 7
Housley, et. al. Standards Track [Page 1]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
3.1 X.509 Version 3 Certificate . . . . . . . . . . . . . . 8
3.2 Certification Paths and Trust . . . . . . . . . . . . . 9
3.3 Revocation . . . . . . . . . . . . . . . . . . . . . . 11
3.4 Operational Protocols . . . . . . . . . . . . . . . . . 13
3.5 Management Protocols . . . . . . . . . . . . . . . . . 13
4 Certificate and Certificate Extensions Profile . . . . . 14
4.1 Basic Certificate Fields . . . . . . . . . . . . . . . 15
4.1.1 Certificate Fields . . . . . . . . . . . . . . . . . 16
4.1.1.1 tbsCertificate . . . . . . . . . . . . . . . . . . 16
4.1.1.2 signatureAlgorithm . . . . . . . . . . . . . . . . 16
4.1.1.3 signatureValue . . . . . . . . . . . . . . . . . . 16
4.1.2 TBSCertificate . . . . . . . . . . . . . . . . . . . 17
4.1.2.1 Version . . . . . . . . . . . . . . . . . . . . . . 17
4.1.2.2 Serial number . . . . . . . . . . . . . . . . . . . 17
4.1.2.3 Signature . . . . . . . . . . . . . . . . . . . . . 18
4.1.2.4 Issuer . . . . . . . . . . . . . . . . . . . . . . 18
4.1.2.5 Validity . . . . . . . . . . . . . . . . . . . . . 22
4.1.2.5.1 UTCTime . . . . . . . . . . . . . . . . . . . . . 22
4.1.2.5.2 GeneralizedTime . . . . . . . . . . . . . . . . . 22
4.1.2.6 Subject . . . . . . . . . . . . . . . . . . . . . . 23
4.1.2.7 Subject Public Key Info . . . . . . . . . . . . . . 24
4.1.2.8 Unique Identifiers . . . . . . . . . . . . . . . . 24
4.1.2.9 Extensions . . . . . . . . . . . . . . . . . . . . . 24
4.2 Certificate Extensions . . . . . . . . . . . . . . . . 24
4.2.1 Standard Extensions . . . . . . . . . . . . . . . . . 25
4.2.1.1 Authority Key Identifier . . . . . . . . . . . . . 26
4.2.1.2 Subject Key Identifier . . . . . . . . . . . . . . 27
4.2.1.3 Key Usage . . . . . . . . . . . . . . . . . . . . . 28
4.2.1.4 Private Key Usage Period . . . . . . . . . . . . . 29
4.2.1.5 Certificate Policies . . . . . . . . . . . . . . . 30
4.2.1.6 Policy Mappings . . . . . . . . . . . . . . . . . . 33
4.2.1.7 Subject Alternative Name . . . . . . . . . . . . . 33
4.2.1.8 Issuer Alternative Name . . . . . . . . . . . . . . 36
4.2.1.9 Subject Directory Attributes . . . . . . . . . . . 36
4.2.1.10 Basic Constraints . . . . . . . . . . . . . . . . 36
4.2.1.11 Name Constraints . . . . . . . . . . . . . . . . . 37
4.2.1.12 Policy Constraints . . . . . . . . . . . . . . . . 40
4.2.1.13 Extended Key Usage . . . . . . . . . . . . . . . . 40
4.2.1.14 CRL Distribution Points . . . . . . . . . . . . . 42
4.2.1.15 Inhibit Any-Policy . . . . . . . . . . . . . . . . 44
4.2.1.16 Freshest CRL . . . . . . . . . . . . . . . . . . . 44
4.2.2 Internet Certificate Extensions . . . . . . . . . . . 45
4.2.2.1 Authority Information Access . . . . . . . . . . . 45
4.2.2.2 Subject Information Access . . . . . . . . . . . . 46
5 CRL and CRL Extensions Profile . . . . . . . . . . . . . 48
5.1 CRL Fields . . . . . . . . . . . . . . . . . . . . . . 49
5.1.1 CertificateList Fields . . . . . . . . . . . . . . . 50
5.1.1.1 tbsCertList . . . . . . . . . . . . . . . . . . . . 50
Housley, et. al. Standards Track [Page 2]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
5.1.1.2 signatureAlgorithm . . . . . . . . . . . . . . . . 50
5.1.1.3 signatureValue . . . . . . . . . . . . . . . . . . 51
5.1.2 Certificate List "To Be Signed" . . . . . . . . . . . 51
5.1.2.1 Version . . . . . . . . . . . . . . . . . . . . . . 52
5.1.2.2 Signature . . . . . . . . . . . . . . . . . . . . . 52
5.1.2.3 Issuer Name . . . . . . . . . . . . . . . . . . . . 52
5.1.2.4 This Update . . . . . . . . . . . . . . . . . . . . 52
5.1.2.5 Next Update . . . . . . . . . . . . . . . . . . . . 53
5.1.2.6 Revoked Certificates . . . . . . . . . . . . . . . 53
5.1.2.7 Extensions . . . . . . . . . . . . . . . . . . . . 53
5.2 CRL Extensions . . . . . . . . . . . . . . . . . . . . 53
5.2.1 Authority Key Identifier . . . . . . . . . . . . . . 54
5.2.2 Issuer Alternative Name . . . . . . . . . . . . . . . 54
5.2.3 CRL Number . . . . . . . . . . . . . . . . . . . . . 55
5.2.4 Delta CRL Indicator . . . . . . . . . . . . . . . . . 55
5.2.5 Issuing Distribution Point . . . . . . . . . . . . . 58
5.2.6 Freshest CRL . . . . . . . . . . . . . . . . . . . . 59
5.3 CRL Entry Extensions . . . . . . . . . . . . . . . . . 60
5.3.1 Reason Code . . . . . . . . . . . . . . . . . . . . . 60
5.3.2 Hold Instruction Code . . . . . . . . . . . . . . . . 61
5.3.3 Invalidity Date . . . . . . . . . . . . . . . . . . . 62
5.3.4 Certificate Issuer . . . . . . . . . . . . . . . . . 62
6 Certificate Path Validation . . . . . . . . . . . . . . . 62
6.1 Basic Path Validation . . . . . . . . . . . . . . . . . 63
6.1.1 Inputs . . . . . . . . . . . . . . . . . . . . . . . 66
6.1.2 Initialization . . . . . . . . . . . . . . . . . . . 67
6.1.3 Basic Certificate Processing . . . . . . . . . . . . 70
6.1.4 Preparation for Certificate i+1 . . . . . . . . . . . 75
6.1.5 Wrap-up procedure . . . . . . . . . . . . . . . . . . 78
6.1.6 Outputs . . . . . . . . . . . . . . . . . . . . . . . 80
6.2 Extending Path Validation . . . . . . . . . . . . . . . 80
6.3 CRL Validation . . . . . . . . . . . . . . . . . . . . 81
6.3.1 Revocation Inputs . . . . . . . . . . . . . . . . . . 82
6.3.2 Initialization and Revocation State Variables . . . . 82
6.3.3 CRL Processing . . . . . . . . . . . . . . . . . . . 83
7 References . . . . . . . . . . . . . . . . . . . . . . . 86
8 Intellectual Property Rights . . . . . . . . . . . . . . 88
9 Security Considerations . . . . . . . . . . . . . . . . . 89
Appendix A. ASN.1 Structures and OIDs . . . . . . . . . . . 92
A.1 Explicitly Tagged Module, 1988 Syntax . . . . . . . . . 92
A.2 Implicitly Tagged Module, 1988 Syntax . . . . . . . . . 105
Appendix B. ASN.1 Notes . . . . . . . . . . . . . . . . . . 112
Appendix C. Examples . . . . . . . . . . . . . . . . . . . 115
C.1 DSA Self-Signed Certificate . . . . . . . . . . . . . . 115
C.2 End Entity Certificate Using DSA . . . . . . . . . . . 119
C.3 End Entity Certificate Using RSA . . . . . . . . . . . 122
C.4 Certificate Revocation List . . . . . . . . . . . . . . 126
Author Addresses . . . . . . . . . . . . . . . . . . . . . . 128
Housley, et. al. Standards Track [Page 3]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
Full Copyright Statement . . . . . . . . . . . . . . . . . . 129
1 Introduction
This specification is one part of a family of standards for the X.509
Public Key Infrastructure (PKI) for the Internet.
This specification profiles the format and semantics of certificates
and certificate revocation lists (CRLs) for the Internet PKI.
Procedures are described for processing of certification paths in the
Internet environment. Finally, ASN.1 modules are provided in the
appendices for all data structures defined or referenced.
Section 2 describes Internet PKI requirements, and the assumptions
which affect the scope of this document. Section 3 presents an
architectural model and describes its relationship to previous IETF
and ISO/IEC/ITU-T standards. In particular, this document's
relationship with the IETF PEM specifications and the ISO/IEC/ITU-T
X.509 documents are described.
Section 4 profiles the X.509 version 3 certificate, and section 5
profiles the X.509 version 2 CRL. The profiles include the
identification of ISO/IEC/ITU-T and ANSI extensions which may be
useful in the Internet PKI. The profiles are presented in the 1988
Abstract Syntax Notation One (ASN.1) rather than the 1997 ASN.1
syntax used in the most recent ISO/IEC/ITU-T standards.
Section 6 includes certification path validation procedures. These
procedures are based upon the ISO/IEC/ITU-T definition.
Implementations are REQUIRED to derive the same results but are not
required to use the specified procedures.
Procedures for identification and encoding of public key materials
and digital signatures are defined in [PKIXALGS]. Implementations of
this specification are not required to use any particular
cryptographic algorithms. However, conforming implementations which
use the algorithms identified in [PKIXALGS] MUST identify and encode
the public key materials and digital signatures as described in that
specification.
Finally, three appendices are provided to aid implementers. Appendix
A contains all ASN.1 structures defined or referenced within this
specification. As above, the material is presented in the 1988
ASN.1. Appendix B contains notes on less familiar features of the
ASN.1 notation used within this specification. Appendix C contains
examples of a conforming certificate and a conforming CRL.
Housley, et. al. Standards Track [Page 4]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
This specification obsoletes RFC 2459. This specification differs
from RFC 2459 in five basic areas:
* To promote interoperable implementations, a detailed algorithm
for certification path validation is included in section 6.1 of
this specification; RFC 2459 provided only a high-level
description of path validation.
* An algorithm for determining the status of a certificate using
CRLs is provided in section 6.3 of this specification. This
material was not present in RFC 2459.
* To accommodate new usage models, detailed information describing
the use of delta CRLs is provided in Section 5 of this
specification.
* Identification and encoding of public key materials and digital
signatures are not included in this specification, but are now
described in a companion specification [PKIXALGS].
* Four additional extensions are specified: three certificate
extensions and one CRL extension. The certificate extensions are
subject info access, inhibit any-policy, and freshest CRL. The
freshest CRL extension is also defined as a CRL extension.
* Throughout the specification, clarifications have been
introduced to enhance consistency with the ITU-T X.509
specification. X.509 defines the certificate and CRL format as
well as many of the extensions that appear in this specification.
These changes were introduced to improve the likelihood of
interoperability between implementations based on this
specification with implementations based on the ITU-T
specification.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
2 Requirements and Assumptions
The goal of this specification is to develop a profile to facilitate
the use of X.509 certificates within Internet applications for those
communities wishing to make use of X.509 technology. Such
applications may include WWW, electronic mail, user authentication,
and IPsec. In order to relieve some of the obstacles to using X.509
Housley, et. al. Standards Track [Page 5]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
certificates, this document defines a profile to promote the
development of certificate management systems; development of
application tools; and interoperability determined by policy.
Some communities will need to supplement, or possibly replace, this
profile in order to meet the requirements of specialized application
domains or environments with additional authorization, assurance, or
operational requirements. However, for basic applications, common
representations of frequently used attributes are defined so that
application developers can obtain necessary information without
regard to the issuer of a particular certificate or certificate
revocation list (CRL).
A certificate user should review the certificate policy generated by
the certification authority (CA) before relying on the authentication
or non-repudiation services associated with the public key in a
particular certificate. To this end, this standard does not
prescribe legally binding rules or duties.
As supplemental authorization and attribute management tools emerge,
such as attribute certificates, it may be appropriate to limit the
authenticated attributes that are included in a certificate. These
other management tools may provide more appropriate methods of
conveying many authenticated attributes.
2.1 Communication and Topology
The users of certificates will operate in a wide range of
environments with respect to their communication topology, especially
users of secure electronic mail. This profile supports users without
high bandwidth, real-time IP connectivity, or high connection
availability. In addition, the profile allows for the presence of
firewall or other filtered communication.
This profile does not assume the deployment of an X.500 Directory
system or a LDAP directory system. The profile does not prohibit the
use of an X.500 Directory or a LDAP directory; however, any means of
distributing certificates and certificate revocation lists (CRLs) may
be used.
2.2 Acceptability Criteria
The goal of the Internet Public Key Infrastructure (PKI) is to meet
the needs of deterministic, automated identification, authentication,
access control, and authorization functions. Support for these
services determines the attributes contained in the certificate as
well as the ancillary control information in the certificate such as
policy data and certification path constraints.
Housley, et. al. Standards Track [Page 6]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
2.3 User Expectations
Users of the Internet PKI are people and processes who use client
software and are the subjects named in certificates. These uses
include readers and writers of electronic mail, the clients for WWW
browsers, WWW servers, and the key manager for IPsec within a router.
This profile recognizes the limitations of the platforms these users
employ and the limitations in sophistication and attentiveness of the
users themselves. This manifests itself in minimal user
configuration responsibility (e.g., trusted CA keys, rules), explicit
platform usage constraints within the certificate, certification path
constraints which shield the user from many malicious actions, and
applications which sensibly automate validation functions.
2.4 Administrator Expectations
As with user expectations, the Internet PKI profile is structured to
support the individuals who generally operate CAs. Providing
administrators with unbounded choices increases the chances that a
subtle CA administrator mistake will result in broad compromise.
Also, unbounded choices greatly complicate the software that process
and validate the certificates created by the CA.
3 Overview of Approach
Following is a simplified view of the architectural model assumed by
the PKIX specifications.
The components in this model are:
end entity: user of PKI certificates and/or end user system that is
the subject of a certificate;
CA: certification authority;
RA: registration authority, i.e., an optional system to which
a CA delegates certain management functions;
CRL issuer: an optional system to which a CA delegates the
publication of certificate revocation lists;
repository: a system or collection of distributed systems that stores
certificates and CRLs and serves as a means of
distributing these certificates and CRLs to end entities.
Note that an Attribute Authority (AA) might also choose to delegate
the publication of CRLs to a CRL issuer.
Housley, et. al. Standards Track [Page 7]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
+---+
| C | +------------+
| e | <-------------------->| End entity |
| r | Operational +------------+
| t | transactions ^
| i | and management | Management
| f | transactions | transactions PKI
| i | | users
| c | v
| a | ======================= +--+------------+ ==============
| t | ^ ^
| e | | | PKI
| | v | management
| & | +------+ | entities
| | <---------------------| RA |<----+ |
| C | Publish certificate +------+ | |
| R | | |
| L | | |
| | v v
| R | +------------+
| e | <------------------------------| CA |
| p | Publish certificate +------------+
| o | Publish CRL ^ ^
| s | | | Management
| i | +------------+ | | transactions
| t | <--------------| CRL Issuer |<----+ |
| o | Publish CRL +------------+ v
| r | +------+
| y | | CA |
+---+ +------+
Figure 1 - PKI Entities
3.1 X.509 Version 3 Certificate
Users of a public key require confidence that the associated private
key is owned by the correct remote subject (person or system) with
which an encryption or digital signature mechanism will be used.
This confidence is obtained through the use of public key
certificates, which are data structures that bind public key values
to subjects. The binding is asserted by having a trusted CA
digitally sign each certificate. The CA may base this assertion upon
technical means (a.k.a., proof of possession through a challenge-
response protocol), presentation of the private key, or on an
assertion by the subject. A certificate has a limited valid lifetime
which is indicated in its signed contents. Because a certificate's
signature and timeliness can be independently checked by a
certificate-using client, certificates can be distributed via
Housley, et. al. Standards Track [Page 8]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
untrusted communications and server systems, and can be cached in
unsecured storage in certificate-using systems.
ITU-T X.509 (formerly CCITT X.509) or ISO/IEC 9594-8, which was first
published in 1988 as part of the X.500 Directory recommendations,
defines a standard certificate format [X.509]. The certificate
format in the 1988 standard is called the version 1 (v1) format.
When X.500 was revised in 1993, two more fields were added, resulting
in the version 2 (v2) format.
The Internet Privacy Enhanced Mail (PEM) RFCs, published in 1993,
include specifications for a public key infrastructure based on X.509
v1 certificates [RFC 1422]. The experience gained in attempts to
deploy RFC 1422 made it clear that the v1 and v2 certificate formats
are deficient in several respects. Most importantly, more fields
were needed to carry information which PEM design and implementation
experience had proven necessary. In response to these new
requirements, ISO/IEC, ITU-T and ANSI X9 developed the X.509 version
3 (v3) certificate format. The v3 format extends the v2 format by
adding provision for additional extension fields. Particular
extension field types may be specified in standards or may be defined
and registered by any organization or community. In June 1996,
standardization of the basic v3 format was completed [X.509].
ISO/IEC, ITU-T, and ANSI X9 have also developed standard extensions
for use in the v3 extensions field [X.509][X9.55]. These extensions
can convey such data as additional subject identification
information, key attribute information, policy information, and
certification path constraints.
However, the ISO/IEC, ITU-T, and ANSI X9 standard extensions are very
broad in their applicability. In order to develop interoperable
implementations of X.509 v3 systems for Internet use, it is necessary
to specify a profile for use of the X.509 v3 extensions tailored for
the Internet. It is one goal of this document to specify a profile
for Internet WWW, electronic mail, and IPsec applications.
Environments with additional requirements may build on this profile
or may replace it.
3.2 Certification Paths and Trust
A user of a security service requiring knowledge of a public key
generally needs to obtain and validate a certificate containing the
required public key. If the public key user does not already hold an
assured copy of the public key of the CA that signed the certificate,
the CA's name, and related information (such as the validity period
or name constraints), then it might need an additional certificate to
obtain that public key. In general, a chain of multiple certificates
Housley, et. al. Standards Track [Page 9]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
may be needed, comprising a certificate of the public key owner (the
end entity) signed by one CA, and zero or more additional
certificates of CAs signed by other CAs. Such chains, called
certification paths, are required because a public key user is only
initialized with a limited number of assured CA public keys.
There are different ways in which CAs might be configured in order
for public key users to be able to find certification paths. For
PEM, RFC 1422 defined a rigid hierarchical structure of CAs. There
are three types of PEM certification authority:
(a) Internet Policy Registration Authority (IPRA): This
authority, operated under the auspices of the Internet Society,
acts as the root of the PEM certification hierarchy at level 1.
It issues certificates only for the next level of authorities,
PCAs. All certification paths start with the IPRA.
(b) Policy Certification Authorities (PCAs): PCAs are at level 2
of the hierarchy, each PCA being certified by the IPRA. A PCA
shall establish and publish a statement of its policy with respect
to certifying users or subordinate certification authorities.
Distinct PCAs aim to satisfy different user needs. For example,
one PCA (an organizational PCA) might support the general
electronic mail needs of commercial organizations, and another PCA
(a high-assurance PCA) might have a more stringent policy designed
for satisfying legally binding digital signature requirements.
(c) Certification Authorities (CAs): CAs are at level 3 of the
hierarchy and can also be at lower levels. Those at level 3 are
certified by PCAs. CAs represent, for example, particular
organizations, particular organizational units (e.g., departments,
groups, sections), or particular geographical areas.
RFC 1422 furthermore has a name subordination rule which requires
that a CA can only issue certificates for entities whose names are
subordinate (in the X.500 naming tree) to the name of the CA itself.
The trust associated with a PEM certification path is implied by the
PCA name. The name subordination rule ensures that CAs below the PCA
are sensibly constrained as to the set of subordinate entities they
can certify (e.g., a CA for an organization can only certify entities
in that organization's name tree). Certificate user systems are able
to mechanically check that the name subordination rule has been
followed.
The RFC 1422 uses the X.509 v1 certificate formats. The limitations
of X.509 v1 required imposition of several structural restrictions to
clearly associate policy information or restrict the utility of
certificates. These restrictions included:
Housley, et. al. Standards Track [Page 10]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(a) a pure top-down hierarchy, with all certification paths
starting from IPRA;
(b) a naming subordination rule restricting the names of a CA's
subjects; and
(c) use of the PCA concept, which requires knowledge of
individual PCAs to be built into certificate chain verification
logic. Knowledge of individual PCAs was required to determine if
a chain could be accepted.
With X.509 v3, most of the requirements addressed by RFC 1422 can be
addressed using certificate extensions, without a need to restrict
the CA structures used. In particular, the certificate extensions
relating to certificate policies obviate the need for PCAs and the
constraint extensions obviate the need for the name subordination
rule. As a result, this document supports a more flexible
architecture, including:
(a) Certification paths start with a public key of a CA in a
user's own domain, or with the public key of the top of a
hierarchy. Starting with the public key of a CA in a user's own
domain has certain advantages. In some environments, the local
domain is the most trusted.
(b) Name constraints may be imposed through explicit inclusion of
a name constraints extension in a certificate, but are not
required.
(c) Policy extensions and policy mappings replace the PCA
concept, which permits a greater degree of automation. The
application can determine if the certification path is acceptable
based on the contents of the certificates instead of a priori
knowledge of PCAs. This permits automation of certification path
processing.
3.3 Revocation
When a certificate is issued, it is expected to be in use for its
entire validity period. However, various circumstances may cause a
certificate to become invalid prior to the expiration of the validity
period. Such circumstances include change of name, change of
association between subject and CA (e.g., an employee terminates
employment with an organization), and compromise or suspected
compromise of the corresponding private key. Under such
circumstances, the CA needs to revoke the certificate.
Housley, et. al. Standards Track [Page 11]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
X.509 defines one method of certificate revocation. This method
involves each CA periodically issuing a signed data structure called
a certificate revocation list (CRL). A CRL is a time stamped list
identifying revoked certificates which is signed by a CA or CRL
issuer and made freely available in a public repository. Each
revoked certificate is identified in a CRL by its certificate serial
number. When a certificate-using system uses a certificate (e.g.,
for verifying a remote user's digital signature), that system not
only checks the certificate signature and validity but also acquires
a suitably-recent CRL and checks that the certificate serial number
is not on that CRL. The meaning of "suitably-recent" may vary with
local policy, but it usually means the most recently-issued CRL. A
new CRL is issued on a regular periodic basis (e.g., hourly, daily,
or weekly). An entry is added to the CRL as part of the next update
following notification of revocation. An entry MUST NOT be removed
from the CRL until it appears on one regularly scheduled CRL issued
beyond the revoked certificate's validity period.
An advantage of this revocation method is that CRLs may be
distributed by exactly the same means as certificates themselves,
namely, via untrusted servers and untrusted communications.
One limitation of the CRL revocation method, using untrusted
communications and servers, is that the time granularity of
revocation is limited to the CRL issue period. For example, if a
revocation is reported now, that revocation will not be reliably
notified to certificate-using systems until all currently issued CRLs
are updated -- this may be up to one hour, one day, or one week
depending on the frequency that CRLs are issued.
As with the X.509 v3 certificate format, in order to facilitate
interoperable implementations from multiple vendors, the X.509 v2 CRL
format needs to be profiled for Internet use. It is one goal of this
document to specify that profile. However, this profile does not
require the issuance of CRLs. Message formats and protocols
supporting on-line revocation notification are defined in other PKIX
specifications. On-line methods of revocation notification may be
applicable in some environments as an alternative to the X.509 CRL.
On-line revocation checking may significantly reduce the latency
between a revocation report and the distribution of the information
to relying parties. Once the CA accepts a revocation report as
authentic and valid, any query to the on-line service will correctly
reflect the certificate validation impacts of the revocation.
However, these methods impose new security requirements: the
certificate validator needs to trust the on-line validation service
while the repository does not need to be trusted.
Housley, et. al. Standards Track [Page 12]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
3.4 Operational Protocols
Operational protocols are required to deliver certificates and CRLs
(or status information) to certificate using client systems.
Provisions are needed for a variety of different means of certificate
and CRL delivery, including distribution procedures based on LDAP,
HTTP, FTP, and X.500. Operational protocols supporting these
functions are defined in other PKIX specifications. These
specifications may include definitions of message formats and
procedures for supporting all of the above operational environments,
including definitions of or references to appropriate MIME content
types.
3.5 Management Protocols
Management protocols are required to support on-line interactions
between PKI user and management entities. For example, a management
protocol might be used between a CA and a client system with which a
key pair is associated, or between two CAs which cross-certify each
other. The set of functions which potentially need to be supported
by management protocols include:
(a) registration: This is the process whereby a user first makes
itself known to a CA (directly, or through an RA), prior to that
CA issuing a certificate or certificates for that user.
(b) initialization: Before a client system can operate securely
it is necessary to install key materials which have the
appropriate relationship with keys stored elsewhere in the
infrastructure. For example, the client needs to be securely
initialized with the public key and other assured information of
the trusted CA(s), to be used in validating certificate paths.
Furthermore, a client typically needs to be initialized with its
own key pair(s).
(c) certification: This is the process in which a CA issues a
certificate for a user's public key, and returns that certificate
to the user's client system and/or posts that certificate in a
repository.
(d) key pair recovery: As an option, user client key materials
(e.g., a user's private key used for encryption purposes) may be
backed up by a CA or a key backup system. If a user needs to
recover these backed up key materials (e.g., as a result of a
forgotten password or a lost key chain file), an on-line protocol
exchange may be needed to support such recovery.
Housley, et. al. Standards Track [Page 13]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(e) key pair update: All key pairs need to be updated regularly,
i.e., replaced with a new key pair, and new certificates issued.
(f) revocation request: An authorized person advises a CA of an
abnormal situation requiring certificate revocation.
(g) cross-certification: Two CAs exchange information used in
establishing a cross-certificate. A cross-certificate is a
certificate issued by one CA to another CA which contains a CA
signature key used for issuing certificates.
Note that on-line protocols are not the only way of implementing the
above functions. For all functions there are off-line methods of
achieving the same result, and this specification does not mandate
use of on-line protocols. For example, when hardware tokens are
used, many of the functions may be achieved as part of the physical
token delivery. Furthermore, some of the above functions may be
combined into one protocol exchange. In particular, two or more of
the registration, initialization, and certification functions can be
combined into one protocol exchange.
The PKIX series of specifications defines a set of standard message
formats supporting the above functions. The protocols for conveying
these messages in different environments (e.g., e-mail, file
transfer, and WWW) are described in those specifications.
4 Certificate and Certificate Extensions Profile
This section presents a profile for public key certificates that will
foster interoperability and a reusable PKI. This section is based
upon the X.509 v3 certificate format and the standard certificate
extensions defined in [X.509]. The ISO/IEC and ITU-T documents use
the 1997 version of ASN.1; while this document uses the 1988 ASN.1
syntax, the encoded certificate and standard extensions are
equivalent. This section also defines private extensions required to
support a PKI for the Internet community.
Certificates may be used in a wide range of applications and
environments covering a broad spectrum of interoperability goals and
a broader spectrum of operational and assurance requirements. The
goal of this document is to establish a common baseline for generic
applications requiring broad interoperability and limited special
purpose requirements. In particular, the emphasis will be on
supporting the use of X.509 v3 certificates for informal Internet
electronic mail, IPsec, and WWW applications.
Housley, et. al. Standards Track [Page 14]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
4.1 Basic Certificate Fields
The X.509 v3 certificate basic syntax is as follows. For signature
calculation, the data that is to be signed is encoded using the ASN.1
distinguished encoding rules (DER) [X.690]. ASN.1 DER encoding is a
tag, length, value encoding system for each element.
Certificate ::= SEQUENCE {
tbsCertificate TBSCertificate,
signatureAlgorithm AlgorithmIdentifier,
signatureValue BIT STRING }
TBSCertificate ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
serialNumber CertificateSerialNumber,
signature AlgorithmIdentifier,
issuer Name,
validity Validity,
subject Name,
subjectPublicKeyInfo SubjectPublicKeyInfo,
issuerUniqueID [1] IMPLICIT UniqueIdentifier OPTIONAL,
-- If present, version MUST be v2 or v3
subjectUniqueID [2] IMPLICIT UniqueIdentifier OPTIONAL,
-- If present, version MUST be v2 or v3
extensions [3] EXPLICIT Extensions OPTIONAL
-- If present, version MUST be v3
}
Version ::= INTEGER { v1(0), v2(1), v3(2) }
CertificateSerialNumber ::= INTEGER
Validity ::= SEQUENCE {
notBefore Time,
notAfter Time }
Time ::= CHOICE {
utcTime UTCTime,
generalTime GeneralizedTime }
UniqueIdentifier ::= BIT STRING
SubjectPublicKeyInfo ::= SEQUENCE {
algorithm AlgorithmIdentifier,
subjectPublicKey BIT STRING }
Extensions ::= SEQUENCE SIZE (1..MAX) OF Extension
Housley, et. al. Standards Track [Page 15]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
Extension ::= SEQUENCE {
extnID OBJECT IDENTIFIER,
critical BOOLEAN DEFAULT FALSE,
extnValue OCTET STRING }
The following items describe the X.509 v3 certificate for use in the
Internet.
4.1.1 Certificate Fields
The Certificate is a SEQUENCE of three required fields. The fields
are described in detail in the following subsections.
4.1.1.1 tbsCertificate
The field contains the names of the subject and issuer, a public key
associated with the subject, a validity period, and other associated
information. The fields are described in detail in section 4.1.2;
the tbsCertificate usually includes extensions which are described in
section 4.2.
4.1.1.2 signatureAlgorithm
The signatureAlgorithm field contains the identifier for the
cryptographic algorithm used by the CA to sign this certificate.
[PKIXALGS] lists supported signature algorithms, but other signature
algorithms MAY also be supported.
An algorithm identifier is defined by the following ASN.1 structure:
AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL }
The algorithm identifier is used to identify a cryptographic
algorithm. The OBJECT IDENTIFIER component identifies the algorithm
(such as DSA with SHA-1). The contents of the optional parameters
field will vary according to the algorithm identified.
This field MUST contain the same algorithm identifier as the
signature field in the sequence tbsCertificate (section 4.1.2.3).
4.1.1.3 signatureValue
The signatureValue field contains a digital signature computed upon
the ASN.1 DER encoded tbsCertificate. The ASN.1 DER encoded
tbsCertificate is used as the input to the signature function. This
Housley, et. al. Standards Track [Page 16]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
signature value is encoded as a BIT STRING and included in the
signature field. The details of this process are specified for each
of algorithms listed in [PKIXALGS].
By generating this signature, a CA certifies the validity of the
information in the tbsCertificate field. In particular, the CA
certifies the binding between the public key material and the subject
of the certificate.
4.1.2 TBSCertificate
The sequence TBSCertificate contains information associated with the
subject of the certificate and the CA who issued it. Every
TBSCertificate contains the names of the subject and issuer, a public
key associated with the subject, a validity period, a version number,
and a serial number; some MAY contain optional unique identifier
fields. The remainder of this section describes the syntax and
semantics of these fields. A TBSCertificate usually includes
extensions. Extensions for the Internet PKI are described in Section
4.2.
4.1.2.1 Version
This field describes the version of the encoded certificate. When
extensions are used, as expected in this profile, version MUST be 3
(value is 2). If no extensions are present, but a UniqueIdentifier
is present, the version SHOULD be 2 (value is 1); however version MAY
be 3. If only basic fields are present, the version SHOULD be 1 (the
value is omitted from the certificate as the default value); however
the version MAY be 2 or 3.
Implementations SHOULD be prepared to accept any version certificate.
At a minimum, conforming implementations MUST recognize version 3
certificates.
Generation of version 2 certificates is not expected by
implementations based on this profile.
4.1.2.2 Serial number
The serial number MUST be a positive integer assigned by the CA to
each certificate. It MUST be unique for each certificate issued by a
given CA (i.e., the issuer name and serial number identify a unique
certificate). CAs MUST force the serialNumber to be a non-negative
integer.
Housley, et. al. Standards Track [Page 17]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
Given the uniqueness requirements above, serial numbers can be
expected to contain long integers. Certificate users MUST be able to
handle serialNumber values up to 20 octets. Conformant CAs MUST NOT
use serialNumber values longer than 20 octets.
Note: Non-conforming CAs may issue certificates with serial numbers
that are negative, or zero. Certificate users SHOULD be prepared to
gracefully handle such certificates.
4.1.2.3 Signature
This field contains the algorithm identifier for the algorithm used
by the CA to sign the certificate.
This field MUST contain the same algorithm identifier as the
signatureAlgorithm field in the sequence Certificate (section
4.1.1.2). The contents of the optional parameters field will vary
according to the algorithm identified. [PKIXALGS] lists the
supported signature algorithms, but other signature algorithms MAY
also be supported.
4.1.2.4 Issuer
The issuer field identifies the entity who has signed and issued the
certificate. The issuer field MUST contain a non-empty distinguished
name (DN). The issuer field is defined as the X.501 type Name
[X.501]. Name is defined by the following ASN.1 structures:
Name ::= CHOICE {
RDNSequence }
RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
RelativeDistinguishedName ::=
SET OF AttributeTypeAndValue
AttributeTypeAndValue ::= SEQUENCE {
type AttributeType,
value AttributeValue }
AttributeType ::= OBJECT IDENTIFIER
AttributeValue ::= ANY DEFINED BY AttributeType
Housley, et. al. Standards Track [Page 18]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
DirectoryString ::= CHOICE {
teletexString TeletexString (SIZE (1..MAX)),
printableString PrintableString (SIZE (1..MAX)),
universalString UniversalString (SIZE (1..MAX)),
utf8String UTF8String (SIZE (1..MAX)),
bmpString BMPString (SIZE (1..MAX)) }
The Name describes a hierarchical name composed of attributes, such
as country name, and corresponding values, such as US. The type of
the component AttributeValue is determined by the AttributeType; in
general it will be a DirectoryString.
The DirectoryString type is defined as a choice of PrintableString,
TeletexString, BMPString, UTF8String, and UniversalString. The
UTF8String encoding [RFC 2279] is the preferred encoding, and all
certificates issued after December 31, 2003 MUST use the UTF8String
encoding of DirectoryString (except as noted below). Until that
date, conforming CAs MUST choose from the following options when
creating a distinguished name, including their own:
(a) if the character set is sufficient, the string MAY be
represented as a PrintableString;
(b) failing (a), if the BMPString character set is sufficient the
string MAY be represented as a BMPString; and
(c) failing (a) and (b), the string MUST be represented as a
UTF8String. If (a) or (b) is satisfied, the CA MAY still choose
to represent the string as a UTF8String.
Exceptions to the December 31, 2003 UTF8 encoding requirements are as
follows:
(a) CAs MAY issue "name rollover" certificates to support an
orderly migration to UTF8String encoding. Such certificates would
include the CA's UTF8String encoded name as issuer and and the old
name encoding as subject, or vice-versa.
(b) As stated in section 4.1.2.6, the subject field MUST be
populated with a non-empty distinguished name matching the
contents of the issuer field in all certificates issued by the
subject CA regardless of encoding.
The TeletexString and UniversalString are included for backward
compatibility, and SHOULD NOT be used for certificates for new
subjects. However, these types MAY be used in certificates where the
name was previously established. Certificate users SHOULD be
prepared to receive certificates with these types.
Housley, et. al. Standards Track [Page 19]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
In addition, many legacy implementations support names encoded in the
ISO 8859-1 character set (Latin1String) [ISO 8859-1] but tag them as
TeletexString. TeletexString encodes a larger character set than ISO
8859-1, but it encodes some characters differently. Implementations
SHOULD be prepared to handle both encodings.
As noted above, distinguished names are composed of attributes. This
specification does not restrict the set of attribute types that may
appear in names. However, conforming implementations MUST be
prepared to receive certificates with issuer names containing the set
of attribute types defined below. This specification RECOMMENDS
support for additional attribute types.
Standard sets of attributes have been defined in the X.500 series of
specifications [X.520]. Implementations of this specification MUST
be prepared to receive the following standard attribute types in
issuer and subject (section 4.1.2.6) names:
* country,
* organization,
* organizational-unit,
* distinguished name qualifier,
* state or province name,
* common name (e.g., "Susan Housley"), and
* serial number.
In addition, implementations of this specification SHOULD be prepared
to receive the following standard attribute types in issuer and
subject names:
* locality,
* title,
* surname,
* given name,
* initials,
* pseudonym, and
* generation qualifier (e.g., "Jr.", "3rd", or "IV").
The syntax and associated object identifiers (OIDs) for these
attribute types are provided in the ASN.1 modules in Appendix A.
In addition, implementations of this specification MUST be prepared
to receive the domainComponent attribute, as defined in [RFC 2247].
The Domain Name System (DNS) provides a hierarchical resource
labeling system. This attribute provides a convenient mechanism for
organizations that wish to use DNs that parallel their DNS names.
This is not a replacement for the dNSName component of the
Housley, et. al. Standards Track [Page 20]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
alternative name field. Implementations are not required to convert
such names into DNS names. The syntax and associated OID for this
attribute type is provided in the ASN.1 modules in Appendix A.
Certificate users MUST be prepared to process the issuer
distinguished name and subject distinguished name (section 4.1.2.6)
fields to perform name chaining for certification path validation
(section 6). Name chaining is performed by matching the issuer
distinguished name in one certificate with the subject name in a CA
certificate.
This specification requires only a subset of the name comparison
functionality specified in the X.500 series of specifications.
Conforming implementations are REQUIRED to implement the following
name comparison rules:
(a) attribute values encoded in different types (e.g.,
PrintableString and BMPString) MAY be assumed to represent
different strings;
(b) attribute values in types other than PrintableString are case
sensitive (this permits matching of attribute values as binary
objects);
(c) attribute values in PrintableString are not case sensitive
(e.g., "Marianne Swanson" is the same as "MARIANNE SWANSON"); and
(d) attribute values in PrintableString are compared after
removing leading and trailing white space and converting internal
substrings of one or more consecutive white space characters to a
single space.
These name comparison rules permit a certificate user to validate
certificates issued using languages or encodings unfamiliar to the
certificate user.
In addition, implementations of this specification MAY use these
comparison rules to process unfamiliar attribute types for name
chaining. This allows implementations to process certificates with
unfamiliar attributes in the issuer name.
Note that the comparison rules defined in the X.500 series of
specifications indicate that the character sets used to encode data
in distinguished names are irrelevant. The characters themselves are
compared without regard to encoding. Implementations of this profile
are permitted to use the comparison algorithm defined in the X.500
series. Such an implementation will recognize a superset of name
matches recognized by the algorithm specified above.
Housley, et. al. Standards Track [Page 21]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
4.1.2.5 Validity
The certificate validity period is the time interval during which the
CA warrants that it will maintain information about the status of the
certificate. The field is represented as a SEQUENCE of two dates:
the date on which the certificate validity period begins (notBefore)
and the date on which the certificate validity period ends
(notAfter). Both notBefore and notAfter may be encoded as UTCTime or
GeneralizedTime.
CAs conforming to this profile MUST always encode certificate
validity dates through the year 2049 as UTCTime; certificate validity
dates in 2050 or later MUST be encoded as GeneralizedTime.
The validity period for a certificate is the period of time from
notBefore through notAfter, inclusive.
4.1.2.5.1 UTCTime
The universal time type, UTCTime, is a standard ASN.1 type intended
for representation of dates and time. UTCTime specifies the year
through the two low order digits and time is specified to the
precision of one minute or one second. UTCTime includes either Z
(for Zulu, or Greenwich Mean Time) or a time differential.
For the purposes of this profile, UTCTime values MUST be expressed
Greenwich Mean Time (Zulu) and MUST include seconds (i.e., times are
YYMMDDHHMMSSZ), even where the number of seconds is zero. Conforming
systems MUST interpret the year field (YY) as follows:
Where YY is greater than or equal to 50, the year SHALL be
interpreted as 19YY; and
Where YY is less than 50, the year SHALL be interpreted as 20YY.
4.1.2.5.2 GeneralizedTime
The generalized time type, GeneralizedTime, is a standard ASN.1 type
for variable precision representation of time. Optionally, the
GeneralizedTime field can include a representation of the time
differential between local and Greenwich Mean Time.
For the purposes of this profile, GeneralizedTime values MUST be
expressed Greenwich Mean Time (Zulu) and MUST include seconds (i.e.,
times are YYYYMMDDHHMMSSZ), even where the number of seconds is zero.
GeneralizedTime values MUST NOT include fractional seconds.
Housley, et. al. Standards Track [Page 22]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
4.1.2.6 Subject
The subject field identifies the entity associated with the public
key stored in the subject public key field. The subject name MAY be
carried in the subject field and/or the subjectAltName extension. If
the subject is a CA (e.g., the basic constraints extension, as
discussed in 4.2.1.10, is present and the value of cA is TRUE), then
the subject field MUST be populated with a non-empty distinguished
name matching the contents of the issuer field (section 4.1.2.4) in
all certificates issued by the subject CA. If the subject is a CRL
issuer (e.g., the key usage extension, as discussed in 4.2.1.3, is
present and the value of cRLSign is TRUE) then the subject field MUST
be populated with a non-empty distinguished name matching the
contents of the issuer field (section 4.1.2.4) in all CRLs issued by
the subject CRL issuer. If subject naming information is present
only in the subjectAltName extension (e.g., a key bound only to an
email address or URI), then the subject name MUST be an empty
sequence and the subjectAltName extension MUST be critical.
Where it is non-empty, the subject field MUST contain an X.500
distinguished name (DN). The DN MUST be unique for each subject
entity certified by the one CA as defined by the issuer name field.
A CA MAY issue more than one certificate with the same DN to the same
subject entity.
The subject name field is defined as the X.501 type Name.
Implementation requirements for this field are those defined for the
issuer field (section 4.1.2.4). When encoding attribute values of
type DirectoryString, the encoding rules for the issuer field MUST be
implemented. Implementations of this specification MUST be prepared
to receive subject names containing the attribute types required for
the issuer field. Implementations of this specification SHOULD be
prepared to receive subject names containing the recommended
attribute types for the issuer field. The syntax and associated
object identifiers (OIDs) for these attribute types are provided in
the ASN.1 modules in Appendix A. Implementations of this
specification MAY use these comparison rules to process unfamiliar
attribute types (i.e., for name chaining). This allows
implementations to process certificates with unfamiliar attributes in
the subject name.
In addition, legacy implementations exist where an RFC 822 name is
embedded in the subject distinguished name as an EmailAddress
attribute. The attribute value for EmailAddress is of type IA5String
to permit inclusion of the character '@', which is not part of the
PrintableString character set. EmailAddress attribute values are not
case sensitive (e.g., "fanfeedback@redsox.com" is the same as
"FANFEEDBACK@REDSOX.COM").
Housley, et. al. Standards Track [Page 23]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
Conforming implementations generating new certificates with
electronic mail addresses MUST use the rfc822Name in the subject
alternative name field (section 4.2.1.7) to describe such identities.
Simultaneous inclusion of the EmailAddress attribute in the subject
distinguished name to support legacy implementations is deprecated
but permitted.
4.1.2.7 Subject Public Key Info
This field is used to carry the public key and identify the algorithm
with which the key is used (e.g., RSA, DSA, or Diffie-Hellman). The
algorithm is identified using the AlgorithmIdentifier structure
specified in section 4.1.1.2. The object identifiers for the
supported algorithms and the methods for encoding the public key
materials (public key and parameters) are specified in [PKIXALGS].
4.1.2.8 Unique Identifiers
These fields MUST only appear if the version is 2 or 3 (section
4.1.2.1). These fields MUST NOT appear if the version is 1. The
subject and issuer unique identifiers are present in the certificate
to handle the possibility of reuse of subject and/or issuer names
over time. This profile RECOMMENDS that names not be reused for
different entities and that Internet certificates not make use of
unique identifiers. CAs conforming to this profile SHOULD NOT
generate certificates with unique identifiers. Applications
conforming to this profile SHOULD be capable of parsing unique
identifiers.
4.1.2.9 Extensions
This field MUST only appear if the version is 3 (section 4.1.2.1).
If present, this field is a SEQUENCE of one or more certificate
extensions. The format and content of certificate extensions in the
Internet PKI is defined in section 4.2.
4.2 Certificate Extensions
The extensions defined for X.509 v3 certificates provide methods for
associating additional attributes with users or public keys and for
managing a certification hierarchy. The X.509 v3 certificate format
also allows communities to define private extensions to carry
information unique to those communities. Each extension in a
certificate is designated as either critical or non-critical. A
certificate using system MUST reject the certificate if it encounters
a critical extension it does not recognize; however, a non-critical
extension MAY be ignored if it is not recognized. The following
sections present recommended extensions used within Internet
Housley, et. al. Standards Track [Page 24]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
certificates and standard locations for information. Communities may
elect to use additional extensions; however, caution ought to be
exercised in adopting any critical extensions in certificates which
might prevent use in a general context.
Each extension includes an OID and an ASN.1 structure. When an
extension appears in a certificate, the OID appears as the field
extnID and the corresponding ASN.1 encoded structure is the value of
the octet string extnValue. A certificate MUST NOT include more than
one instance of a particular extension. For example, a certificate
may contain only one authority key identifier extension (section
4.2.1.1). An extension includes the boolean critical, with a default
value of FALSE. The text for each extension specifies the acceptable
values for the critical field.
Conforming CAs MUST support key identifiers (sections 4.2.1.1 and
4.2.1.2), basic constraints (section 4.2.1.10), key usage (section
4.2.1.3), and certificate policies (section 4.2.1.5) extensions. If
the CA issues certificates with an empty sequence for the subject
field, the CA MUST support the subject alternative name extension
(section 4.2.1.7). Support for the remaining extensions is OPTIONAL.
Conforming CAs MAY support extensions that are not identified within
this specification; certificate issuers are cautioned that marking
such extensions as critical may inhibit interoperability.
At a minimum, applications conforming to this profile MUST recognize
the following extensions: key usage (section 4.2.1.3), certificate
policies (section 4.2.1.5), the subject alternative name (section
4.2.1.7), basic constraints (section 4.2.1.10), name constraints
(section 4.2.1.11), policy constraints (section 4.2.1.12), extended
key usage (section 4.2.1.13), and inhibit any-policy (section
4.2.1.15).
In addition, applications conforming to this profile SHOULD recognize
the authority and subject key identifier (sections 4.2.1.1 and
4.2.1.2), and policy mapping (section 4.2.1.6) extensions.
4.2.1 Standard Extensions
This section identifies standard certificate extensions defined in
[X.509] for use in the Internet PKI. Each extension is associated
with an OID defined in [X.509]. These OIDs are members of the id-ce
arc, which is defined by the following:
id-ce OBJECT IDENTIFIER ::= { joint-iso-ccitt(2) ds(5) 29 }
Housley, et. al. Standards Track [Page 25]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
4.2.1.1 Authority Key Identifier
The authority key identifier extension provides a means of
identifying the public key corresponding to the private key used to
sign a certificate. This extension is used where an issuer has
multiple signing keys (either due to multiple concurrent key pairs or
due to changeover). The identification MAY be based on either the
key identifier (the subject key identifier in the issuer's
certificate) or on the issuer name and serial number.
The keyIdentifier field of the authorityKeyIdentifier extension MUST
be included in all certificates generated by conforming CAs to
facilitate certification path construction. There is one exception;
where a CA distributes its public key in the form of a "self-signed"
certificate, the authority key identifier MAY be omitted. The
signature on a self-signed certificate is generated with the private
key associated with the certificate's subject public key. (This
proves that the issuer possesses both the public and private keys.)
In this case, the subject and authority key identifiers would be
identical, but only the subject key identifier is needed for
certification path building.
The value of the keyIdentifier field SHOULD be derived from the
public key used to verify the certificate's signature or a method
that generates unique values. Two common methods for generating key
identifiers from the public key, and one common method for generating
unique values, are described in section 4.2.1.2. Where a key
identifier has not been previously established, this specification
RECOMMENDS use of one of these methods for generating keyIdentifiers.
Where a key identifier has been previously established, the CA SHOULD
use the previously established identifier.
This profile RECOMMENDS support for the key identifier method by all
certificate users.
This extension MUST NOT be marked critical.
id-ce-authorityKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 35 }
AuthorityKeyIdentifier ::= SEQUENCE {
keyIdentifier [0] KeyIdentifier OPTIONAL,
authorityCertIssuer [1] GeneralNames OPTIONAL,
authorityCertSerialNumber [2] CertificateSerialNumber OPTIONAL }
KeyIdentifier ::= OCTET STRING
Housley, et. al. Standards Track [Page 26]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
4.2.1.2 Subject Key Identifier
The subject key identifier extension provides a means of identifying
certificates that contain a particular public key.
To facilitate certification path construction, this extension MUST
appear in all conforming CA certificates, that is, all certificates
including the basic constraints extension (section 4.2.1.10) where
the value of cA is TRUE. The value of the subject key identifier
MUST be the value placed in the key identifier field of the Authority
Key Identifier extension (section 4.2.1.1) of certificates issued by
the subject of this certificate.
For CA certificates, subject key identifiers SHOULD be derived from
the public key or a method that generates unique values. Two common
methods for generating key identifiers from the public key are:
(1) The keyIdentifier is composed of the 160-bit SHA-1 hash of the
value of the BIT STRING subjectPublicKey (excluding the tag,
length, and number of unused bits).
(2) The keyIdentifier is composed of a four bit type field with
the value 0100 followed by the least significant 60 bits of the
SHA-1 hash of the value of the BIT STRING subjectPublicKey
(excluding the tag, length, and number of unused bit string bits).
One common method for generating unique values is a monotonically
increasing sequence of integers.
For end entity certificates, the subject key identifier extension
provides a means for identifying certificates containing the
particular public key used in an application. Where an end entity
has obtained multiple certificates, especially from multiple CAs, the
subject key identifier provides a means to quickly identify the set
of certificates containing a particular public key. To assist
applications in identifying the appropriate end entity certificate,
this extension SHOULD be included in all end entity certificates.
For end entity certificates, subject key identifiers SHOULD be
derived from the public key. Two common methods for generating key
identifiers from the public key are identified above.
Where a key identifier has not been previously established, this
specification RECOMMENDS use of one of these methods for generating
keyIdentifiers. Where a key identifier has been previously
established, the CA SHOULD use the previously established identifier.
This extension MUST NOT be marked critical.
Housley, et. al. Standards Track [Page 27]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
id-ce-subjectKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 14 }
SubjectKeyIdentifier ::= KeyIdentifier
4.2.1.3 Key Usage
The key usage extension defines the purpose (e.g., encipherment,
signature, certificate signing) of the key contained in the
certificate. The usage restriction might be employed when a key that
could be used for more than one operation is to be restricted. For
example, when an RSA key should be used only to verify signatures on
objects other than public key certificates and CRLs, the
digitalSignature and/or nonRepudiation bits would be asserted.
Likewise, when an RSA key should be used only for key management, the
keyEncipherment bit would be asserted.
This extension MUST appear in certificates that contain public keys
that are used to validate digital signatures on other public key
certificates or CRLs. When this extension appears, it SHOULD be
marked critical.
id-ce-keyUsage OBJECT IDENTIFIER ::= { id-ce 15 }
KeyUsage ::= BIT STRING {
digitalSignature (0),
nonRepudiation (1),
keyEncipherment (2),
dataEncipherment (3),
keyAgreement (4),
keyCertSign (5),
cRLSign (6),
encipherOnly (7),
decipherOnly (8) }
Bits in the KeyUsage type are used as follows:
The digitalSignature bit is asserted when the subject public key
is used with a digital signature mechanism to support security
services other than certificate signing (bit 5), or CRL signing
(bit 6). Digital signature mechanisms are often used for entity
authentication and data origin authentication with integrity.
The nonRepudiation bit is asserted when the subject public key is
used to verify digital signatures used to provide a non-
repudiation service which protects against the signing entity
falsely denying some action, excluding certificate or CRL signing.
In the case of later conflict, a reliable third party may
determine the authenticity of the signed data.
Housley, et. al. Standards Track [Page 28]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
Further distinctions between the digitalSignature and
nonRepudiation bits may be provided in specific certificate
policies.
The keyEncipherment bit is asserted when the subject public key is
used for key transport. For example, when an RSA key is to be
used for key management, then this bit is set.
The dataEncipherment bit is asserted when the subject public key
is used for enciphering user data, other than cryptographic keys.
The keyAgreement bit is asserted when the subject public key is
used for key agreement. For example, when a Diffie-Hellman key is
to be used for key management, then this bit is set.
The keyCertSign bit is asserted when the subject public key is
used for verifying a signature on public key certificates. If the
keyCertSign bit is asserted, then the cA bit in the basic
constraints extension (section 4.2.1.10) MUST also be asserted.
The cRLSign bit is asserted when the subject public key is used
for verifying a signature on certificate revocation list (e.g., a
CRL, delta CRL, or an ARL). This bit MUST be asserted in
certificates that are used to verify signatures on CRLs.
The meaning of the encipherOnly bit is undefined in the absence of
the keyAgreement bit. When the encipherOnly bit is asserted and
the keyAgreement bit is also set, the subject public key may be
used only for enciphering data while performing key agreement.
The meaning of the decipherOnly bit is undefined in the absence of
the keyAgreement bit. When the decipherOnly bit is asserted and
the keyAgreement bit is also set, the subject public key may be
used only for deciphering data while performing key agreement.
This profile does not restrict the combinations of bits that may be
set in an instantiation of the keyUsage extension. However,
appropriate values for keyUsage extensions for particular algorithms
are specified in [PKIXALGS].
4.2.1.4 Private Key Usage Period
This extension SHOULD NOT be used within the Internet PKI. CAs
conforming to this profile MUST NOT generate certificates that
include a critical private key usage period extension.
Housley, et. al. Standards Track [Page 29]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
The private key usage period extension allows the certificate issuer
to specify a different validity period for the private key than the
certificate. This extension is intended for use with digital
signature keys. This extension consists of two optional components,
notBefore and notAfter. The private key associated with the
certificate SHOULD NOT be used to sign objects before or after the
times specified by the two components, respectively. CAs conforming
to this profile MUST NOT generate certificates with private key usage
period extensions unless at least one of the two components is
present and the extension is non-critical.
Where used, notBefore and notAfter are represented as GeneralizedTime
and MUST be specified and interpreted as defined in section
4.1.2.5.2.
id-ce-privateKeyUsagePeriod OBJECT IDENTIFIER ::= { id-ce 16 }
PrivateKeyUsagePeriod ::= SEQUENCE {
notBefore [0] GeneralizedTime OPTIONAL,
notAfter [1] GeneralizedTime OPTIONAL }
4.2.1.5 Certificate Policies
The certificate policies extension contains a sequence of one or more
policy information terms, each of which consists of an object
identifier (OID) and optional qualifiers. Optional qualifiers, which
MAY be present, are not expected to change the definition of the
policy.
In an end entity certificate, these policy information terms indicate
the policy under which the certificate has been issued and the
purposes for which the certificate may be used. In a CA certificate,
these policy information terms limit the set of policies for
certification paths which include this certificate. When a CA does
not wish to limit the set of policies for certification paths which
include this certificate, it MAY assert the special policy anyPolicy,
with a value of { 2 5 29 32 0 }.
Applications with specific policy requirements are expected to have a
list of those policies which they will accept and to compare the
policy OIDs in the certificate to that list. If this extension is
critical, the path validation software MUST be able to interpret this
extension (including the optional qualifier), or MUST reject the
certificate.
To promote interoperability, this profile RECOMMENDS that policy
information terms consist of only an OID. Where an OID alone is
insufficient, this profile strongly recommends that use of qualifiers
Housley, et. al. Standards Track [Page 30]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
be limited to those identified in this section. When qualifiers are
used with the special policy anyPolicy, they MUST be limited to the
qualifiers identified in this section.
This specification defines two policy qualifier types for use by
certificate policy writers and certificate issuers. The qualifier
types are the CPS Pointer and User Notice qualifiers.
The CPS Pointer qualifier contains a pointer to a Certification
Practice Statement (CPS) published by the CA. The pointer is in the
form of a URI. Processing requirements for this qualifier are a
local matter. No action is mandated by this specification regardless
of the criticality value asserted for the extension.
User notice is intended for display to a relying party when a
certificate is used. The application software SHOULD display all
user notices in all certificates of the certification path used,
except that if a notice is duplicated only one copy need be
displayed. To prevent such duplication, this qualifier SHOULD only
be present in end entity certificates and CA certificates issued to
other organizations.
The user notice has two optional fields: the noticeRef field and the
explicitText field.
The noticeRef field, if used, names an organization and
identifies, by number, a particular textual statement prepared by
that organization. For example, it might identify the
organization "CertsRUs" and notice number 1. In a typical
implementation, the application software will have a notice file
containing the current set of notices for CertsRUs; the
application will extract the notice text from the file and display
it. Messages MAY be multilingual, allowing the software to select
the particular language message for its own environment.
An explicitText field includes the textual statement directly in
the certificate. The explicitText field is a string with a
maximum size of 200 characters.
If both the noticeRef and explicitText options are included in the
one qualifier and if the application software can locate the notice
text indicated by the noticeRef option, then that text SHOULD be
displayed; otherwise, the explicitText string SHOULD be displayed.
Note: While the explicitText has a maximum size of 200 characters,
some non-conforming CAs exceed this limit. Therefore, certificate
users SHOULD gracefully handle explicitText with more than 200
characters.
Housley, et. al. Standards Track [Page 31]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
id-ce-certificatePolicies OBJECT IDENTIFIER ::= { id-ce 32 }
anyPolicy OBJECT IDENTIFIER ::= { id-ce-certificate-policies 0 }
certificatePolicies ::= SEQUENCE SIZE (1..MAX) OF PolicyInformation
PolicyInformation ::= SEQUENCE {
policyIdentifier CertPolicyId,
policyQualifiers SEQUENCE SIZE (1..MAX) OF
PolicyQualifierInfo OPTIONAL }
CertPolicyId ::= OBJECT IDENTIFIER
PolicyQualifierInfo ::= SEQUENCE {
policyQualifierId PolicyQualifierId,
qualifier ANY DEFINED BY policyQualifierId }
-- policyQualifierIds for Internet policy qualifiers
id-qt OBJECT IDENTIFIER ::= { id-pkix 2 }
id-qt-cps OBJECT IDENTIFIER ::= { id-qt 1 }
id-qt-unotice OBJECT IDENTIFIER ::= { id-qt 2 }
PolicyQualifierId ::=
OBJECT IDENTIFIER ( id-qt-cps | id-qt-unotice )
Qualifier ::= CHOICE {
cPSuri CPSuri,
userNotice UserNotice }
CPSuri ::= IA5String
UserNotice ::= SEQUENCE {
noticeRef NoticeReference OPTIONAL,
explicitText DisplayText OPTIONAL}
NoticeReference ::= SEQUENCE {
organization DisplayText,
noticeNumbers SEQUENCE OF INTEGER }
DisplayText ::= CHOICE {
ia5String IA5String (SIZE (1..200)),
visibleString VisibleString (SIZE (1..200)),
bmpString BMPString (SIZE (1..200)),
utf8String UTF8String (SIZE (1..200)) }
Housley, et. al. Standards Track [Page 32]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
4.2.1.6 Policy Mappings
This extension is used in CA certificates. It lists one or more
pairs of OIDs; each pair includes an issuerDomainPolicy and a
subjectDomainPolicy. The pairing indicates the issuing CA considers
its issuerDomainPolicy equivalent to the subject CA's
subjectDomainPolicy.
The issuing CA's users might accept an issuerDomainPolicy for certain
applications. The policy mapping defines the list of policies
associated with the subject CA that may be accepted as comparable to
the issuerDomainPolicy.
Each issuerDomainPolicy named in the policy mapping extension SHOULD
also be asserted in a certificate policies extension in the same
certificate. Policies SHOULD NOT be mapped either to or from the
special value anyPolicy (section 4.2.1.5).
This extension MAY be supported by CAs and/or applications, and it
MUST be non-critical.
id-ce-policyMappings OBJECT IDENTIFIER ::= { id-ce 33 }
PolicyMappings ::= SEQUENCE SIZE (1..MAX) OF SEQUENCE {
issuerDomainPolicy CertPolicyId,
subjectDomainPolicy CertPolicyId }
4.2.1.7 Subject Alternative Name
The subject alternative names extension allows additional identities
to be bound to the subject of the certificate. Defined options
include an Internet electronic mail address, a DNS name, an IP
address, and a uniform resource identifier (URI). Other options
exist, including completely local definitions. Multiple name forms,
and multiple instances of each name form, MAY be included. Whenever
such identities are to be bound into a certificate, the subject
alternative name (or issuer alternative name) extension MUST be used;
however, a DNS name MAY be represented in the subject field using the
domainComponent attribute as described in section 4.1.2.4.
Because the subject alternative name is considered to be definitively
bound to the public key, all parts of the subject alternative name
MUST be verified by the CA.
Further, if the only subject identity included in the certificate is
an alternative name form (e.g., an electronic mail address), then the
subject distinguished name MUST be empty (an empty sequence), and the
Housley, et. al. Standards Track [Page 33]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
subjectAltName extension MUST be present. If the subject field
contains an empty sequence, the subjectAltName extension MUST be
marked critical.
When the subjectAltName extension contains an Internet mail address,
the address MUST be included as an rfc822Name. The format of an
rfc822Name is an "addr-spec" as defined in RFC 822 [RFC 822]. An
addr-spec has the form "local-part@domain". Note that an addr-spec
has no phrase (such as a common name) before it, has no comment (text
surrounded in parentheses) after it, and is not surrounded by "<" and
">". Note that while upper and lower case letters are allowed in an
RFC 822 addr-spec, no significance is attached to the case.
When the subjectAltName extension contains a iPAddress, the address
MUST be stored in the octet string in "network byte order," as
specified in RFC 791 [RFC 791]. The least significant bit (LSB) of
each octet is the LSB of the corresponding byte in the network
address. For IP Version 4, as specified in RFC 791, the octet string
MUST contain exactly four octets. For IP Version 6, as specified in
RFC 1883, the octet string MUST contain exactly sixteen octets [RFC
1883].
When the subjectAltName extension contains a domain name system
label, the domain name MUST be stored in the dNSName (an IA5String).
The name MUST be in the "preferred name syntax," as specified by RFC
1034 [RFC 1034]. Note that while upper and lower case letters are
allowed in domain names, no signifigance is attached to the case. In
addition, while the string " " is a legal domain name, subjectAltName
extensions with a dNSName of " " MUST NOT be used. Finally, the use
of the DNS representation for Internet mail addresses (wpolk.nist.gov
instead of wpolk@nist.gov) MUST NOT be used; such identities are to
be encoded as rfc822Name.
Note: work is currently underway to specify domain names in
international character sets. Such names will likely not be
accommodated by IA5String. Once this work is complete, this profile
will be revisited and the appropriate functionality will be added.
When the subjectAltName extension contains a URI, the name MUST be
stored in the uniformResourceIdentifier (an IA5String). The name
MUST NOT be a relative URL, and it MUST follow the URL syntax and
encoding rules specified in [RFC 1738]. The name MUST include both a
scheme (e.g., "http" or "ftp") and a scheme-specific-part. The
scheme-specific-part MUST include a fully qualified domain name or IP
address as the host.
Housley, et. al. Standards Track [Page 34]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
As specified in [RFC 1738], the scheme name is not case-sensitive
(e.g., "http" is equivalent to "HTTP"). The host part is also not
case-sensitive, but other components of the scheme-specific-part may
be case-sensitive. When comparing URIs, conforming implementations
MUST compare the scheme and host without regard to case, but assume
the remainder of the scheme-specific-part is case sensitive.
When the subjectAltName extension contains a DN in the directoryName,
the DN MUST be unique for each subject entity certified by the one CA
as defined by the issuer name field. A CA MAY issue more than one
certificate with the same DN to the same subject entity.
The subjectAltName MAY carry additional name types through the use of
the otherName field. The format and semantics of the name are
indicated through the OBJECT IDENTIFIER in the type-id field. The
name itself is conveyed as value field in otherName. For example,
Kerberos [RFC 1510] format names can be encoded into the otherName,
using using a Kerberos 5 principal name OID and a SEQUENCE of the
Realm and the PrincipalName.
Subject alternative names MAY be constrained in the same manner as
subject distinguished names using the name constraints extension as
described in section 4.2.1.11.
If the subjectAltName extension is present, the sequence MUST contain
at least one entry. Unlike the subject field, conforming CAs MUST
NOT issue certificates with subjectAltNames containing empty
GeneralName fields. For example, an rfc822Name is represented as an
IA5String. While an empty string is a valid IA5String, such an
rfc822Name is not permitted by this profile. The behavior of clients
that encounter such a certificate when processing a certificication
path is not defined by this profile.
Finally, the semantics of subject alternative names that include
wildcard characters (e.g., as a placeholder for a set of names) are
not addressed by this specification. Applications with specific
requirements MAY use such names, but they must define the semantics.
id-ce-subjectAltName OBJECT IDENTIFIER ::= { id-ce 17 }
SubjectAltName ::= GeneralNames
GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
Housley, et. al. Standards Track [Page 35]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
GeneralName ::= CHOICE {
otherName [0] OtherName,
rfc822Name [1] IA5String,
dNSName [2] IA5String,
x400Address [3] ORAddress,
directoryName [4] Name,
ediPartyName [5] EDIPartyName,
uniformResourceIdentifier [6] IA5String,
iPAddress [7] OCTET STRING,
registeredID [8] OBJECT IDENTIFIER }
OtherName ::= SEQUENCE {
type-id OBJECT IDENTIFIER,
value [0] EXPLICIT ANY DEFINED BY type-id }
EDIPartyName ::= SEQUENCE {
nameAssigner [0] DirectoryString OPTIONAL,
partyName [1] DirectoryString }
4.2.1.8 Issuer Alternative Names
As with 4.2.1.7, this extension is used to associate Internet style
identities with the certificate issuer. Issuer alternative names
MUST be encoded as in 4.2.1.7.
Where present, this extension SHOULD NOT be marked critical.
id-ce-issuerAltName OBJECT IDENTIFIER ::= { id-ce 18 }
IssuerAltName ::= GeneralNames
4.2.1.9 Subject Directory Attributes
The subject directory attributes extension is used to convey
identification attributes (e.g., nationality) of the subject. The
extension is defined as a sequence of one or more attributes. This
extension MUST be non-critical.
id-ce-subjectDirectoryAttributes OBJECT IDENTIFIER ::= { id-ce 9 }
SubjectDirectoryAttributes ::= SEQUENCE SIZE (1..MAX) OF Attribute
4.2.1.10 Basic Constraints
The basic constraints extension identifies whether the subject of the
certificate is a CA and the maximum depth of valid certification
paths that include this certificate.
Housley, et. al. Standards Track [Page 36]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
The cA boolean indicates whether the certified public key belongs to
a CA. If the cA boolean is not asserted, then the keyCertSign bit in
the key usage extension MUST NOT be asserted.
The pathLenConstraint field is meaningful only if the cA boolean is
asserted and the key usage extension asserts the keyCertSign bit
(section 4.2.1.3). In this case, it gives the maximum number of non-
self-issued intermediate certificates that may follow this
certificate in a valid certification path. A certificate is self-
issued if the DNs that appear in the subject and issuer fields are
identical and are not empty. (Note: The last certificate in the
certification path is not an intermediate certificate, and is not
included in this limit. Usually, the last certificate is an end
entity certificate, but it can be a CA certificate.) A
pathLenConstraint of zero indicates that only one more certificate
may follow in a valid certification path. Where it appears, the
pathLenConstraint field MUST be greater than or equal to zero. Where
pathLenConstraint does not appear, no limit is imposed.
This extension MUST appear as a critical extension in all CA
certificates that contain public keys used to validate digital
signatures on certificates. This extension MAY appear as a critical
or non-critical extension in CA certificates that contain public keys
used exclusively for purposes other than validating digital
signatures on certificates. Such CA certificates include ones that
contain public keys used exclusively for validating digital
signatures on CRLs and ones that contain key management public keys
used with certificate enrollment protocols. This extension MAY
appear as a critical or non-critical extension in end entity
certificates.
CAs MUST NOT include the pathLenConstraint field unless the cA
boolean is asserted and the key usage extension asserts the
keyCertSign bit.
id-ce-basicConstraints OBJECT IDENTIFIER ::= { id-ce 19 }
BasicConstraints ::= SEQUENCE {
cA BOOLEAN DEFAULT FALSE,
pathLenConstraint INTEGER (0..MAX) OPTIONAL }
4.2.1.11 Name Constraints
The name constraints extension, which MUST be used only in a CA
certificate, indicates a name space within which all subject names in
subsequent certificates in a certification path MUST be located.
Restrictions apply to the subject distinguished name and apply to
subject alternative names. Restrictions apply only when the
Housley, et. al. Standards Track [Page 37]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
specified name form is present. If no name of the type is in the
certificate, the certificate is acceptable.
Name constraints are not applied to certificates whose issuer and
subject are identical (unless the certificate is the final
certificate in the path). (This could prevent CAs that use name
constraints from employing self-issued certificates to implement key
rollover.)
Restrictions are defined in terms of permitted or excluded name
subtrees. Any name matching a restriction in the excludedSubtrees
field is invalid regardless of information appearing in the
permittedSubtrees. This extension MUST be critical.
Within this profile, the minimum and maximum fields are not used with
any name forms, thus minimum MUST be zero, and maximum MUST be
absent.
For URIs, the constraint applies to the host part of the name. The
constraint MAY specify a host or a domain. Examples would be
"foo.bar.com"; and ".xyz.com". When the the constraint begins with
a period, it MAY be expanded with one or more subdomains. That is,
the constraint ".xyz.com" is satisfied by both abc.xyz.com and
abc.def.xyz.com. However, the constraint ".xyz.com" is not satisfied
by "xyz.com". When the constraint does not begin with a period, it
specifies a host.
A name constraint for Internet mail addresses MAY specify a
particular mailbox, all addresses at a particular host, or all
mailboxes in a domain. To indicate a particular mailbox, the
constraint is the complete mail address. For example, "root@xyz.com"
indicates the root mailbox on the host "xyz.com". To indicate all
Internet mail addresses on a particular host, the constraint is
specified as the host name. For example, the constraint "xyz.com" is
satisfied by any mail address at the host "xyz.com". To specify any
address within a domain, the constraint is specified with a leading
period (as with URIs). For example, ".xyz.com" indicates all the
Internet mail addresses in the domain "xyz.com", but not Internet
mail addresses on the host "xyz.com".
DNS name restrictions are expressed as foo.bar.com. Any DNS name
that can be constructed by simply adding to the left hand side of the
name satisfies the name constraint. For example, www.foo.bar.com
would satisfy the constraint but foo1.bar.com would not.
Legacy implementations exist where an RFC 822 name is embedded in the
subject distinguished name in an attribute of type EmailAddress
(section 4.1.2.6). When rfc822 names are constrained, but the
Housley, et. al. Standards Track [Page 38]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
certificate does not include a subject alternative name, the rfc822
name constraint MUST be applied to the attribute of type EmailAddress
in the subject distinguished name. The ASN.1 syntax for EmailAddress
and the corresponding OID are supplied in Appendix A.
Restrictions of the form directoryName MUST be applied to the subject
field in the certificate and to the subjectAltName extensions of type
directoryName. Restrictions of the form x400Address MUST be applied
to subjectAltName extensions of type x400Address.
When applying restrictions of the form directoryName, an
implementation MUST compare DN attributes. At a minimum,
implementations MUST perform the DN comparison rules specified in
Section 4.1.2.4. CAs issuing certificates with a restriction of the
form directoryName SHOULD NOT rely on implementation of the full ISO
DN name comparison algorithm. This implies name restrictions MUST be
stated identically to the encoding used in the subject field or
subjectAltName extension.
The syntax of iPAddress MUST be as described in section 4.2.1.7 with
the following additions specifically for Name Constraints. For IPv4
addresses, the ipAddress field of generalName MUST contain eight (8)
octets, encoded in the style of RFC 1519 (CIDR) to represent an
address range [RFC 1519]. For IPv6 addresses, the ipAddress field
MUST contain 32 octets similarly encoded. For example, a name
constraint for "class C" subnet 10.9.8.0 is represented as the octets
0A 09 08 00 FF FF FF 00, representing the CIDR notation
10.9.8.0/255.255.255.0.
The syntax and semantics for name constraints for otherName,
ediPartyName, and registeredID are not defined by this specification.
id-ce-nameConstraints OBJECT IDENTIFIER ::= { id-ce 30 }
NameConstraints ::= SEQUENCE {
permittedSubtrees [0] GeneralSubtrees OPTIONAL,
excludedSubtrees [1] GeneralSubtrees OPTIONAL }
GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
GeneralSubtree ::= SEQUENCE {
base GeneralName,
minimum [0] BaseDistance DEFAULT 0,
maximum [1] BaseDistance OPTIONAL }
BaseDistance ::= INTEGER (0..MAX)
Housley, et. al. Standards Track [Page 39]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
4.2.1.12 Policy Constraints
The policy constraints extension can be used in certificates issued
to CAs. The policy constraints extension constrains path validation
in two ways. It can be used to prohibit policy mapping or require
that each certificate in a path contain an acceptable policy
identifier.
If the inhibitPolicyMapping field is present, the value indicates the
number of additional certificates that may appear in the path before
policy mapping is no longer permitted. For example, a value of one
indicates that policy mapping may be processed in certificates issued
by the subject of this certificate, but not in additional
certificates in the path.
If the requireExplicitPolicy field is present, the value of
requireExplicitPolicy indicates the number of additional certificates
that may appear in the path before an explicit policy is required for
the entire path. When an explicit policy is required, it is
necessary for all certificates in the path to contain an acceptable
policy identifier in the certificate policies extension. An
acceptable policy identifier is the identifier of a policy required
by the user of the certification path or the identifier of a policy
which has been declared equivalent through policy mapping.
Conforming CAs MUST NOT issue certificates where policy constraints
is a empty sequence. That is, at least one of the
inhibitPolicyMapping field or the requireExplicitPolicy field MUST be
present. The behavior of clients that encounter a empty policy
constraints field is not addressed in this profile.
This extension MAY be critical or non-critical.
id-ce-policyConstraints OBJECT IDENTIFIER ::= { id-ce 36 }
PolicyConstraints ::= SEQUENCE {
requireExplicitPolicy [0] SkipCerts OPTIONAL,
inhibitPolicyMapping [1] SkipCerts OPTIONAL }
SkipCerts ::= INTEGER (0..MAX)
4.2.1.13 Extended Key Usage
This extension indicates one or more purposes for which the certified
public key may be used, in addition to or in place of the basic
purposes indicated in the key usage extension. In general, this
extension will appear only in end entity certificates. This
extension is defined as follows:
Housley, et. al. Standards Track [Page 40]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
id-ce-extKeyUsage OBJECT IDENTIFIER ::= { id-ce 37 }
ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
KeyPurposeId ::= OBJECT IDENTIFIER
Key purposes may be defined by any organization with a need. Object
identifiers used to identify key purposes MUST be assigned in
accordance with IANA or ITU-T Recommendation X.660 [X.660].
This extension MAY, at the option of the certificate issuer, be
either critical or non-critical.
If the extension is present, then the certificate MUST only be used
for one of the purposes indicated. If multiple purposes are
indicated the application need not recognize all purposes indicated,
as long as the intended purpose is present. Certificate using
applications MAY require that a particular purpose be indicated in
order for the certificate to be acceptable to that application.
If a CA includes extended key usages to satisfy such applications,
but does not wish to restrict usages of the key, the CA can include
the special keyPurposeID anyExtendedKeyUsage. If the
anyExtendedKeyUsage keyPurposeID is present, the extension SHOULD NOT
be critical.
If a certificate contains both a key usage extension and an extended
key usage extension, then both extensions MUST be processed
independently and the certificate MUST only be used for a purpose
consistent with both extensions. If there is no purpose consistent
with both extensions, then the certificate MUST NOT be used for any
purpose.
The following key usage purposes are defined:
anyExtendedKeyUsage OBJECT IDENTIFIER ::= { id-ce-extKeyUsage 0 }
id-kp OBJECT IDENTIFIER ::= { id-pkix 3 }
id-kp-serverAuth OBJECT IDENTIFIER ::= { id-kp 1 }
-- TLS WWW server authentication
-- Key usage bits that may be consistent: digitalSignature,
-- keyEncipherment or keyAgreement
id-kp-clientAuth OBJECT IDENTIFIER ::= { id-kp 2 }
-- TLS WWW client authentication
-- Key usage bits that may be consistent: digitalSignature
-- and/or keyAgreement
Housley, et. al. Standards Track [Page 41]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
id-kp-codeSigning OBJECT IDENTIFIER ::= { id-kp 3 }
-- Signing of downloadable executable code
-- Key usage bits that may be consistent: digitalSignature
id-kp-emailProtection OBJECT IDENTIFIER ::= { id-kp 4 }
-- E-mail protection
-- Key usage bits that may be consistent: digitalSignature,
-- nonRepudiation, and/or (keyEncipherment or keyAgreement)
id-kp-timeStamping OBJECT IDENTIFIER ::= { id-kp 8 }
-- Binding the hash of an object to a time
-- Key usage bits that may be consistent: digitalSignature
-- and/or nonRepudiation
id-kp-OCSPSigning OBJECT IDENTIFIER ::= { id-kp 9 }
-- Signing OCSP responses
-- Key usage bits that may be consistent: digitalSignature
-- and/or nonRepudiation
4.2.1.14 CRL Distribution Points
The CRL distribution points extension identifies how CRL information
is obtained. The extension SHOULD be non-critical, but this profile
RECOMMENDS support for this extension by CAs and applications.
Further discussion of CRL management is contained in section 5.
The cRLDistributionPoints extension is a SEQUENCE of
DistributionPoint. A DistributionPoint consists of three fields,
each of which is optional: distributionPoint, reasons, and cRLIssuer.
While each of these fields is optional, a DistributionPoint MUST NOT
consist of only the reasons field; either distributionPoint or
cRLIssuer MUST be present. If the certificate issuer is not the CRL
issuer, then the cRLIssuer field MUST be present and contain the Name
of the CRL issuer. If the certificate issuer is also the CRL issuer,
then the cRLIssuer field MUST be omitted and the distributionPoint
field MUST be present. If the distributionPoint field is omitted,
cRLIssuer MUST be present and include a Name corresponding to an
X.500 or LDAP directory entry where the CRL is located.
When the distributionPoint field is present, it contains either a
SEQUENCE of general names or a single value, nameRelativeToCRLIssuer.
If the cRLDistributionPoints extension contains a general name of
type URI, the following semantics MUST be assumed: the URI is a
pointer to the current CRL for the associated reasons and will be
issued by the associated cRLIssuer. The expected values for the URI
are those defined in 4.2.1.7. Processing rules for other values are
not defined by this specification.
Housley, et. al. Standards Track [Page 42]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
If the DistributionPointName contains multiple values, each name
describes a different mechanism to obtain the same CRL. For example,
the same CRL could be available for retrieval through both LDAP and
HTTP.
If the DistributionPointName contains the single value
nameRelativeToCRLIssuer, the value provides a distinguished name
fragment. The fragment is appended to the X.500 distinguished name
of the CRL issuer to obtain the distribution point name. If the
cRLIssuer field in the DistributionPoint is present, then the name
fragment is appended to the distinguished name that it contains;
otherwise, the name fragment is appended to the certificate issuer
distinguished name. The DistributionPointName MUST NOT use the
nameRealtiveToCRLIssuer alternative when cRLIssuer contains more than
one distinguished name.
If the DistributionPoint omits the reasons field, the CRL MUST
include revocation information for all reasons.
The cRLIssuer identifies the entity who signs and issues the CRL. If
present, the cRLIssuer MUST contain at least one an X.500
distinguished name (DN), and MAY also contain other name forms.
Since the cRLIssuer is compared to the CRL issuer name, the X.501
type Name MUST follow the encoding rules for the issuer name field in
the certificate (section 4.1.2.4).
id-ce-cRLDistributionPoints OBJECT IDENTIFIER ::= { id-ce 31 }
CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
DistributionPoint ::= SEQUENCE {
distributionPoint [0] DistributionPointName OPTIONAL,
reasons [1] ReasonFlags OPTIONAL,
cRLIssuer [2] GeneralNames OPTIONAL }
DistributionPointName ::= CHOICE {
fullName [0] GeneralNames,
nameRelativeToCRLIssuer [1] RelativeDistinguishedName }
Housley, et. al. Standards Track [Page 43]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
ReasonFlags ::= BIT STRING {
unused (0),
keyCompromise (1),
cACompromise (2),
affiliationChanged (3),
superseded (4),
cessationOfOperation (5),
certificateHold (6),
privilegeWithdrawn (7),
aACompromise (8) }
4.2.1.15 Inhibit Any-Policy
The inhibit any-policy extension can be used in certificates issued
to CAs. The inhibit any-policy indicates that the special anyPolicy
OID, with the value { 2 5 29 32 0 }, is not considered an explicit
match for other certificate policies. The value indicates the number
of additional certificates that may appear in the path before
anyPolicy is no longer permitted. For example, a value of one
indicates that anyPolicy may be processed in certificates issued by
the subject of this certificate, but not in additional certificates
in the path.
This extension MUST be critical.
id-ce-inhibitAnyPolicy OBJECT IDENTIFIER ::= { id-ce 54 }
InhibitAnyPolicy ::= SkipCerts
SkipCerts ::= INTEGER (0..MAX)
4.2.1.16 Freshest CRL (a.k.a. Delta CRL Distribution Point)
The freshest CRL extension identifies how delta CRL information is
obtained. The extension MUST be non-critical. Further discussion of
CRL management is contained in section 5.
The same syntax is used for this extension and the
cRLDistributionPoints extension, and is described in section
4.2.1.14. The same conventions apply to both extensions.
id-ce-freshestCRL OBJECT IDENTIFIER ::= { id-ce 46 }
FreshestCRL ::= CRLDistributionPoints
Housley, et. al. Standards Track [Page 44]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
4.2.2 Private Internet Extensions
This section defines two extensions for use in the Internet Public
Key Infrastructure. These extensions may be used to direct
applications to on-line information about the issuing CA or the
subject. As the information may be available in multiple forms, each
extension is a sequence of IA5String values, each of which represents
a URI. The URI implicitly specifies the location and format of the
information and the method for obtaining the information.
An object identifier is defined for the private extension. The
object identifier associated with the private extension is defined
under the arc id-pe within the arc id-pkix. Any future extensions
defined for the Internet PKI are also expected to be defined under
the arc id-pe.
id-pkix OBJECT IDENTIFIER ::=
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) }
id-pe OBJECT IDENTIFIER ::= { id-pkix 1 }
4.2.2.1 Authority Information Access
The authority information access extension indicates how to access CA
information and services for the issuer of the certificate in which
the extension appears. Information and services may include on-line
validation services and CA policy data. (The location of CRLs is not
specified in this extension; that information is provided by the
cRLDistributionPoints extension.) This extension may be included in
end entity or CA certificates, and it MUST be non-critical.
id-pe-authorityInfoAccess OBJECT IDENTIFIER ::= { id-pe 1 }
AuthorityInfoAccessSyntax ::=
SEQUENCE SIZE (1..MAX) OF AccessDescription
AccessDescription ::= SEQUENCE {
accessMethod OBJECT IDENTIFIER,
accessLocation GeneralName }
id-ad OBJECT IDENTIFIER ::= { id-pkix 48 }
id-ad-caIssuers OBJECT IDENTIFIER ::= { id-ad 2 }
id-ad-ocsp OBJECT IDENTIFIER ::= { id-ad 1 }
Housley, et. al. Standards Track [Page 45]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
Each entry in the sequence AuthorityInfoAccessSyntax describes the
format and location of additional information provided by the CA that
issued the certificate in which this extension appears. The type and
format of the information is specified by the accessMethod field; the
accessLocation field specifies the location of the information. The
retrieval mechanism may be implied by the accessMethod or specified
by accessLocation.
This profile defines two accessMethod OIDs: id-ad-caIssuers and
id-ad-ocsp.
The id-ad-caIssuers OID is used when the additional information lists
CAs that have issued certificates superior to the CA that issued the
certificate containing this extension. The referenced CA issuers
description is intended to aid certificate users in the selection of
a certification path that terminates at a point trusted by the
certificate user.
When id-ad-caIssuers appears as accessMethod, the accessLocation
field describes the referenced description server and the access
protocol to obtain the referenced description. The accessLocation
field is defined as a GeneralName, which can take several forms.
Where the information is available via http, ftp, or ldap,
accessLocation MUST be a uniformResourceIdentifier. Where the
information is available via the Directory Access Protocol (DAP),
accessLocation MUST be a directoryName. The entry for that
directoryName contains CA certificates in the crossCertificatePair
attribute. When the information is available via electronic mail,
accessLocation MUST be an rfc822Name. The semantics of other
id-ad-caIssuers accessLocation name forms are not defined.
The id-ad-ocsp OID is used when revocation information for the
certificate containing this extension is available using the Online
Certificate Status Protocol (OCSP) [RFC 2560].
When id-ad-ocsp appears as accessMethod, the accessLocation field is
the location of the OCSP responder, using the conventions defined in
[RFC 2560].
Additional access descriptors may be defined in other PKIX
specifications.
4.2.2.2 Subject Information Access
The subject information access extension indicates how to access
information and services for the subject of the certificate in which
the extension appears. When the subject is a CA, information and
services may include certificate validation services and CA policy
Housley, et. al. Standards Track [Page 46]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
data. When the subject is an end entity, the information describes
the type of services offered and how to access them. In this case,
the contents of this extension are defined in the protocol
specifications for the suported services. This extension may be
included in subject or CA certificates, and it MUST be non-critical.
id-pe-subjectInfoAccess OBJECT IDENTIFIER ::= { id-pe 11 }
SubjectInfoAccessSyntax ::=
SEQUENCE SIZE (1..MAX) OF AccessDescription
AccessDescription ::= SEQUENCE {
accessMethod OBJECT IDENTIFIER,
accessLocation GeneralName }
Each entry in the sequence SubjectInfoAccessSyntax describes the
format and location of additional information provided by the subject
of the certificate in which this extension appears. The type and
format of the information is specified by the accessMethod field; the
accessLocation field specifies the location of the information. The
retrieval mechanism may be implied by the accessMethod or specified
by accessLocation.
This profile defines one access method to be used when the subject is
a CA, and one access method to be used when the subject is an end
entity. Additional access methods may be defined in the future in
the protocol specifications for other services.
The id-ad-caRepository OID is used when the subject is a CA, and
publishes its certificates and CRLs (if issued) in a repository. The
accessLocation field is defined as a GeneralName, which can take
several forms. Where the information is available via http, ftp, or
ldap, accessLocation MUST be a uniformResourceIdentifier. Where the
information is available via the directory access protocol (dap),
accessLocation MUST be a directoryName. When the information is
available via electronic mail, accessLocation MUST be an rfc822Name.
The semantics of other name forms of of accessLocation (when
accessMethod is id-ad-caRepository) are not defined by this
specification.
The id-ad-timeStamping OID is used when the subject offers
timestamping services using the Time Stamp Protocol defined in
[PKIXTSA]. Where the timestamping services are available via http or
ftp, accessLocation MUST be a uniformResourceIdentifier. Where the
timestamping services are available via electronic mail,
accessLocation MUST be an rfc822Name. Where timestamping services
Housley, et. al. Standards Track [Page 47]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
are available using TCP/IP, the dNSName or ipAddress name forms may
be used. The semantics of other name forms of accessLocation (when
accessMethod is id-ad-timeStamping) are not defined by this
specification.
Additional access descriptors may be defined in other PKIX
specifications.
id-ad OBJECT IDENTIFIER ::= { id-pkix 48 }
id-ad-caRepository OBJECT IDENTIFIER ::= { id-ad 5 }
id-ad-timeStamping OBJECT IDENTIFIER ::= { id-ad 3 }
5 CRL and CRL Extensions Profile
As discussed above, one goal of this X.509 v2 CRL profile is to
foster the creation of an interoperable and reusable Internet PKI.
To achieve this goal, guidelines for the use of extensions are
specified, and some assumptions are made about the nature of
information included in the CRL.
CRLs may be used in a wide range of applications and environments
covering a broad spectrum of interoperability goals and an even
broader spectrum of operational and assurance requirements. This
profile establishes a common baseline for generic applications
requiring broad interoperability. The profile defines a set of
information that can be expected in every CRL. Also, the profile
defines common locations within the CRL for frequently used
attributes as well as common representations for these attributes.
CRL issuers issue CRLs. In general, the CRL issuer is the CA. CAs
publish CRLs to provide status information about the certificates
they issued. However, a CA may delegate this responsibility to
another trusted authority. Whenever the CRL issuer is not the CA
that issued the certificates, the CRL is referred to as an indirect
CRL.
Each CRL has a particular scope. The CRL scope is the set of
certificates that could appear on a given CRL. For example, the
scope could be "all certificates issued by CA X", "all CA
certificates issued by CA X", "all certificates issued by CA X that
have been revoked for reasons of key compromise and CA compromise",
or could be a set of certificates based on arbitrary local
information, such as "all certificates issued to the NIST employees
located in Boulder".
Housley, et. al. Standards Track [Page 48]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
A complete CRL lists all unexpired certificates, within its scope,
that have been revoked for one of the revocation reasons covered by
the CRL scope. The CRL issuer MAY also generate delta CRLs. A delta
CRL only lists those certificates, within its scope, whose revocation
status has changed since the issuance of a referenced complete CRL.
The referenced complete CRL is referred to as a base CRL. The scope
of a delta CRL MUST be the same as the base CRL that it references.
This profile does not define any private Internet CRL extensions or
CRL entry extensions.
Environments with additional or special purpose requirements may
build on this profile or may replace it.
Conforming CAs are not required to issue CRLs if other revocation or
certificate status mechanisms are provided. When CRLs are issued,
the CRLs MUST be version 2 CRLs, include the date by which the next
CRL will be issued in the nextUpdate field (section 5.1.2.5), include
the CRL number extension (section 5.2.3), and include the authority
key identifier extension (section 5.2.1). Conforming applications
that support CRLs are REQUIRED to process both version 1 and version
2 complete CRLs that provide revocation information for all
certificates issued by one CA. Conforming applications are NOT
REQUIRED to support processing of delta CRLs, indirect CRLs, or CRLs
with a scope other than all certificates issued by one CA.
5.1 CRL Fields
The X.509 v2 CRL syntax is as follows. For signature calculation,
the data that is to be signed is ASN.1 DER encoded. ASN.1 DER
encoding is a tag, length, value encoding system for each element.
CertificateList ::= SEQUENCE {
tbsCertList TBSCertList,
signatureAlgorithm AlgorithmIdentifier,
signatureValue BIT STRING }
Housley, et. al. Standards Track [Page 49]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
TBSCertList ::= SEQUENCE {
version Version OPTIONAL,
-- if present, MUST be v2
signature AlgorithmIdentifier,
issuer Name,
thisUpdate Time,
nextUpdate Time OPTIONAL,
revokedCertificates SEQUENCE OF SEQUENCE {
userCertificate CertificateSerialNumber,
revocationDate Time,
crlEntryExtensions Extensions OPTIONAL
-- if present, MUST be v2
} OPTIONAL,
crlExtensions [0] EXPLICIT Extensions OPTIONAL
-- if present, MUST be v2
}
-- Version, Time, CertificateSerialNumber, and Extensions
-- are all defined in the ASN.1 in section 4.1
-- AlgorithmIdentifier is defined in section 4.1.1.2
The following items describe the use of the X.509 v2 CRL in the
Internet PKI.
5.1.1 CertificateList Fields
The CertificateList is a SEQUENCE of three required fields. The
fields are described in detail in the following subsections.
5.1.1.1 tbsCertList
The first field in the sequence is the tbsCertList. This field is
itself a sequence containing the name of the issuer, issue date,
issue date of the next list, the optional list of revoked
certificates, and optional CRL extensions. When there are no revoked
certificates, the revoked certificates list is absent. When one or
more certificates are revoked, each entry on the revoked certificate
list is defined by a sequence of user certificate serial number,
revocation date, and optional CRL entry extensions.
5.1.1.2 signatureAlgorithm
The signatureAlgorithm field contains the algorithm identifier for
the algorithm used by the CRL issuer to sign the CertificateList.
The field is of type AlgorithmIdentifier, which is defined in section
4.1.1.2. [PKIXALGS] lists the supported algorithms for this
specification, but other signature algorithms MAY also be supported.
Housley, et. al. Standards Track [Page 50]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
This field MUST contain the same algorithm identifier as the
signature field in the sequence tbsCertList (section 5.1.2.2).
5.1.1.3 signatureValue
The signatureValue field contains a digital signature computed upon
the ASN.1 DER encoded tbsCertList. The ASN.1 DER encoded tbsCertList
is used as the input to the signature function. This signature value
is encoded as a BIT STRING and included in the CRL signatureValue
field. The details of this process are specified for each of the
supported algorithms in [PKIXALGS].
CAs that are also CRL issuers MAY use one private key to digitally
sign certificates and CRLs, or MAY use separate private keys to
digitally sign certificates and CRLs. When separate private keys are
employed, each of the public keys associated with these private keys
is placed in a separate certificate, one with the keyCertSign bit set
in the key usage extension, and one with the cRLSign bit set in the
key usage extension (section 4.2.1.3). When separate private keys
are employed, certificates issued by the CA contain one authority key
identifier, and the corresponding CRLs contain a different authority
key identifier. The use of separate CA certificates for validation
of certificate signatures and CRL signatures can offer improved
security characteristics; however, it imposes a burden on
applications, and it might limit interoperability. Many applications
construct a certification path, and then validate the certification
path (section 6). CRL checking in turn requires a separate
certification path to be constructed and validated for the CA's CRL
signature validation certificate. Applications that perform CRL
checking MUST support certification path validation when certificates
and CRLs are digitally signed with the same CA private key. These
applications SHOULD support certification path validation when
certificates and CRLs are digitally signed with different CA private
keys.
5.1.2 Certificate List "To Be Signed"
The certificate list to be signed, or TBSCertList, is a sequence of
required and optional fields. The required fields identify the CRL
issuer, the algorithm used to sign the CRL, the date and time the CRL
was issued, and the date and time by which the CRL issuer will issue
the next CRL.
Optional fields include lists of revoked certificates and CRL
extensions. The revoked certificate list is optional to support the
case where a CA has not revoked any unexpired certificates that it
Housley, et. al. Standards Track [Page 51]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
has issued. The profile requires conforming CRL issuers to use the
CRL number and authority key identifier CRL extensions in all CRLs
issued.
5.1.2.1 Version
This optional field describes the version of the encoded CRL. When
extensions are used, as required by this profile, this field MUST be
present and MUST specify version 2 (the integer value is 1).
5.1.2.2 Signature
This field contains the algorithm identifier for the algorithm used
to sign the CRL. [PKIXALGS] lists OIDs for the most popular
signature algorithms used in the Internet PKI.
This field MUST contain the same algorithm identifier as the
signatureAlgorithm field in the sequence CertificateList (section
5.1.1.2).
5.1.2.3 Issuer Name
The issuer name identifies the entity who has signed and issued the
CRL. The issuer identity is carried in the issuer name field.
Alternative name forms may also appear in the issuerAltName extension
(section 5.2.2). The issuer name field MUST contain an X.500
distinguished name (DN). The issuer name field is defined as the
X.501 type Name, and MUST follow the encoding rules for the issuer
name field in the certificate (section 4.1.2.4).
5.1.2.4 This Update
This field indicates the issue date of this CRL. ThisUpdate may be
encoded as UTCTime or GeneralizedTime.
CRL issuers conforming to this profile MUST encode thisUpdate as
UTCTime for dates through the year 2049. CRL issuers conforming to
this profile MUST encode thisUpdate as GeneralizedTime for dates in
the year 2050 or later.
Where encoded as UTCTime, thisUpdate MUST be specified and
interpreted as defined in section 4.1.2.5.1. Where encoded as
GeneralizedTime, thisUpdate MUST be specified and interpreted as
defined in section 4.1.2.5.2.
Housley, et. al. Standards Track [Page 52]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
5.1.2.5 Next Update
This field indicates the date by which the next CRL will be issued.
The next CRL could be issued before the indicated date, but it will
not be issued any later than the indicated date. CRL issuers SHOULD
issue CRLs with a nextUpdate time equal to or later than all previous
CRLs. nextUpdate may be encoded as UTCTime or GeneralizedTime.
This profile requires inclusion of nextUpdate in all CRLs issued by
conforming CRL issuers. Note that the ASN.1 syntax of TBSCertList
describes this field as OPTIONAL, which is consistent with the ASN.1
structure defined in [X.509]. The behavior of clients processing
CRLs which omit nextUpdate is not specified by this profile.
CRL issuers conforming to this profile MUST encode nextUpdate as
UTCTime for dates through the year 2049. CRL issuers conforming to
this profile MUST encode nextUpdate as GeneralizedTime for dates in
the year 2050 or later.
Where encoded as UTCTime, nextUpdate MUST be specified and
interpreted as defined in section 4.1.2.5.1. Where encoded as
GeneralizedTime, nextUpdate MUST be specified and interpreted as
defined in section 4.1.2.5.2.
5.1.2.6 Revoked Certificates
When there are no revoked certificates, the revoked certificates list
MUST be absent. Otherwise, revoked certificates are listed by their
serial numbers. Certificates revoked by the CA are uniquely
identified by the certificate serial number. The date on which the
revocation occurred is specified. The time for revocationDate MUST
be expressed as described in section 5.1.2.4. Additional information
may be supplied in CRL entry extensions; CRL entry extensions are
discussed in section 5.3.
5.1.2.7 Extensions
This field may only appear if the version is 2 (section 5.1.2.1). If
present, this field is a sequence of one or more CRL extensions. CRL
extensions are discussed in section 5.2.
5.2 CRL Extensions
The extensions defined by ANSI X9, ISO/IEC, and ITU-T for X.509 v2
CRLs [X.509] [X9.55] provide methods for associating additional
attributes with CRLs. The X.509 v2 CRL format also allows
communities to define private extensions to carry information unique
to those communities. Each extension in a CRL may be designated as
Housley, et. al. Standards Track [Page 53]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
critical or non-critical. A CRL validation MUST fail if it
encounters a critical extension which it does not know how to
process. However, an unrecognized non-critical extension may be
ignored. The following subsections present those extensions used
within Internet CRLs. Communities may elect to include extensions in
CRLs which are not defined in this specification. However, caution
should be exercised in adopting any critical extensions in CRLs which
might be used in a general context.
Conforming CRL issuers are REQUIRED to include the authority key
identifier (section 5.2.1) and the CRL number (section 5.2.3)
extensions in all CRLs issued.
5.2.1 Authority Key Identifier
The authority key identifier extension provides a means of
identifying the public key corresponding to the private key used to
sign a CRL. The identification can be based on either the key
identifier (the subject key identifier in the CRL signer's
certificate) or on the issuer name and serial number. This extension
is especially useful where an issuer has more than one signing key,
either due to multiple concurrent key pairs or due to changeover.
Conforming CRL issuers MUST use the key identifier method, and MUST
include this extension in all CRLs issued.
The syntax for this CRL extension is defined in section 4.2.1.1.
5.2.2 Issuer Alternative Name
The issuer alternative names extension allows additional identities
to be associated with the issuer of the CRL. Defined options include
an rfc822 name (electronic mail address), a DNS name, an IP address,
and a URI. Multiple instances of a name and multiple name forms may
be included. Whenever such identities are used, the issuer
alternative name extension MUST be used; however, a DNS name MAY be
represented in the issuer field using the domainComponent attribute
as described in section 4.1.2.4.
The issuerAltName extension SHOULD NOT be marked critical.
The OID and syntax for this CRL extension are defined in section
4.2.1.8.
Housley, et. al. Standards Track [Page 54]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
5.2.3 CRL Number
The CRL number is a non-critical CRL extension which conveys a
monotonically increasing sequence number for a given CRL scope and
CRL issuer. This extension allows users to easily determine when a
particular CRL supersedes another CRL. CRL numbers also support the
identification of complementary complete CRLs and delta CRLs. CRL
issuers conforming to this profile MUST include this extension in all
CRLs.
If a CRL issuer generates delta CRLs in addition to complete CRLs for
a given scope, the complete CRLs and delta CRLs MUST share one
numbering sequence. If a delta CRL and a complete CRL that cover the
same scope are issued at the same time, they MUST have the same CRL
number and provide the same revocation information. That is, the
combination of the delta CRL and an acceptable complete CRL MUST
provide the same revocation information as the simultaneously issued
complete CRL.
If a CRL issuer generates two CRLs (two complete CRLs, two delta
CRLs, or a complete CRL and a delta CRL) for the same scope at
different times, the two CRLs MUST NOT have the same CRL number.
That is, if the this update field (section 5.1.2.4) in the two CRLs
are not identical, the CRL numbers MUST be different.
Given the requirements above, CRL numbers can be expected to contain
long integers. CRL verifiers MUST be able to handle CRLNumber values
up to 20 octets. Conformant CRL issuers MUST NOT use CRLNumber
values longer than 20 octets.
id-ce-cRLNumber OBJECT IDENTIFIER ::= { id-ce 20 }
CRLNumber ::= INTEGER (0..MAX)
5.2.4 Delta CRL Indicator
The delta CRL indicator is a critical CRL extension that identifies a
CRL as being a delta CRL. Delta CRLs contain updates to revocation
information previously distributed, rather than all the information
that would appear in a complete CRL. The use of delta CRLs can
significantly reduce network load and processing time in some
environments. Delta CRLs are generally smaller than the CRLs they
update, so applications that obtain delta CRLs consume less network
bandwidth than applications that obtain the corresponding complete
CRLs. Applications which store revocation information in a format
other than the CRL structure can add new revocation information to
the local database without reprocessing information.
Housley, et. al. Standards Track [Page 55]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
The delta CRL indicator extension contains the single value of type
BaseCRLNumber. The CRL number identifies the CRL, complete for a
given scope, that was used as the starting point in the generation of
this delta CRL. A conforming CRL issuer MUST publish the referenced
base CRL as a complete CRL. The delta CRL contains all updates to
the revocation status for that same scope. The combination of a
delta CRL plus the referenced base CRL is equivalent to a complete
CRL, for the applicable scope, at the time of publication of the
delta CRL.
When a conforming CRL issuer generates a delta CRL, the delta CRL
MUST include a critical delta CRL indicator extension.
When a delta CRL is issued, it MUST cover the same set of reasons and
the same set of certificates that were covered by the base CRL it
references. That is, the scope of the delta CRL MUST be the same as
the scope of the complete CRL referenced as the base. The referenced
base CRL and the delta CRL MUST omit the issuing distribution point
extension or contain identical issuing distribution point extensions.
Further, the CRL issuer MUST use the same private key to sign the
delta CRL and any complete CRL that it can be used to update.
An application that supports delta CRLs can construct a CRL that is
complete for a given scope by combining a delta CRL for that scope
with either an issued CRL that is complete for that scope or a
locally constructed CRL that is complete for that scope.
When a delta CRL is combined with a complete CRL or a locally
constructed CRL, the resulting locally constructed CRL has the CRL
number specified in the CRL number extension found in the delta CRL
used in its construction. In addition, the resulting locally
constructed CRL has the thisUpdate and nextUpdate times specified in
the corresponding fields of the delta CRL used in its construction.
In addition, the locally constructed CRL inherits the issuing
distribution point from the delta CRL.
A complete CRL and a delta CRL MAY be combined if the following four
conditions are satisfied:
(a) The complete CRL and delta CRL have the same issuer.
(b) The complete CRL and delta CRL have the same scope. The two
CRLs have the same scope if either of the following conditions are
met:
(1) The issuingDistributionPoint extension is omitted from
both the complete CRL and the delta CRL.
Housley, et. al. Standards Track [Page 56]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(2) The issuingDistributionPoint extension is present in both
the complete CRL and the delta CRL, and the values for each of
the fields in the extensions are the same in both CRLs.
(c) The CRL number of the complete CRL is equal to or greater
than the BaseCRLNumber specified in the delta CRL. That is, the
complete CRL contains (at a minimum) all the revocation
information held by the referenced base CRL.
(d) The CRL number of the complete CRL is less than the CRL
number of the delta CRL. That is, the delta CRL follows the
complete CRL in the numbering sequence.
CRL issuers MUST ensure that the combination of a delta CRL and any
appropriate complete CRL accurately reflects the current revocation
status. The CRL issuer MUST include an entry in the delta CRL for
each certificate within the scope of the delta CRL whose status has
changed since the generation of the referenced base CRL:
(a) If the certificate is revoked for a reason included in the
scope of the CRL, list the certificate as revoked.
(b) If the certificate is valid and was listed on the referenced
base CRL or any subsequent CRL with reason code certificateHold,
and the reason code certificateHold is included in the scope of
the CRL, list the certificate with the reason code removeFromCRL.
(c) If the certificate is revoked for a reason outside the scope
of the CRL, but the certificate was listed on the referenced base
CRL or any subsequent CRL with a reason code included in the scope
of this CRL, list the certificate as revoked but omit the reason
code.
(d) If the certificate is revoked for a reason outside the scope
of the CRL and the certificate was neither listed on the
referenced base CRL nor any subsequent CRL with a reason code
included in the scope of this CRL, do not list the certificate on
this CRL.
The status of a certificate is considered to have changed if it is
revoked, placed on hold, released from hold, or if its revocation
reason changes.
It is appropriate to list a certificate with reason code
removeFromCRL on a delta CRL even if the certificate was not on hold
in the referenced base CRL. If the certificate was placed on hold in
Housley, et. al. Standards Track [Page 57]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
any CRL issued after the base but before this delta CRL and then
released from hold, it MUST be listed on the delta CRL with
revocation reason removeFromCRL.
A CRL issuer MAY optionally list a certificate on a delta CRL with
reason code removeFromCRL if the notAfter time specified in the
certificate precedes the thisUpdate time specified in the delta CRL
and the certificate was listed on the referenced base CRL or in any
CRL issued after the base but before this delta CRL.
If a certificate revocation notice first appears on a delta CRL, then
it is possible for the certificate validity period to expire before
the next complete CRL for the same scope is issued. In this case,
the revocation notice MUST be included in all subsequent delta CRLs
until the revocation notice is included on at least one explicitly
issued complete CRL for this scope.
An application that supports delta CRLs MUST be able to construct a
current complete CRL by combining a previously issued complete CRL
and the most current delta CRL. An application that supports delta
CRLs MAY also be able to construct a current complete CRL by
combining a previously locally constructed complete CRL and the
current delta CRL. A delta CRL is considered to be the current one
if the current time is between the times contained in the thisUpdate
and nextUpdate fields. Under some circumstances, the CRL issuer may
publish one or more delta CRLs before indicated by the nextUpdate
field. If more than one current delta CRL for a given scope is
encountered, the application SHOULD consider the one with the latest
value in thisUpdate to be the most current one.
id-ce-deltaCRLIndicator OBJECT IDENTIFIER ::= { id-ce 27 }
BaseCRLNumber ::= CRLNumber
5.2.5 Issuing Distribution Point
The issuing distribution point is a critical CRL extension that
identifies the CRL distribution point and scope for a particular CRL,
and it indicates whether the CRL covers revocation for end entity
certificates only, CA certificates only, attribute certificates only,
or a limited set of reason codes. Although the extension is
critical, conforming implementations are not required to support this
extension.
Housley, et. al. Standards Track [Page 58]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
The CRL is signed using the CRL issuer's private key. CRL
Distribution Points do not have their own key pairs. If the CRL is
stored in the X.500 Directory, it is stored in the Directory entry
corresponding to the CRL distribution point, which may be different
than the Directory entry of the CRL issuer.
The reason codes associated with a distribution point MUST be
specified in onlySomeReasons. If onlySomeReasons does not appear,
the distribution point MUST contain revocations for all reason codes.
CAs may use CRL distribution points to partition the CRL on the basis
of compromise and routine revocation. In this case, the revocations
with reason code keyCompromise (1), cACompromise (2), and
aACompromise (8) appear in one distribution point, and the
revocations with other reason codes appear in another distribution
point.
If the distributionPoint field is present and contains a URI, the
following semantics MUST be assumed: the object is a pointer to the
most current CRL issued by this CRL issuer. The URI schemes ftp,
http, mailto [RFC1738] and ldap [RFC1778] are defined for this
purpose. The URI MUST be an absolute pathname, not a relative
pathname, and MUST specify the host.
If the distributionPoint field is absent, the CRL MUST contain
entries for all revoked unexpired certificates issued by the CRL
issuer, if any, within the scope of the CRL.
The CRL issuer MUST assert the indirectCRL boolean, if the scope of
the CRL includes certificates issued by authorities other than the
CRL issuer. The authority responsible for each entry is indicated by
the certificate issuer CRL entry extension (section 5.3.4).
id-ce-issuingDistributionPoint OBJECT IDENTIFIER ::= { id-ce 28 }
issuingDistributionPoint ::= SEQUENCE {
distributionPoint [0] DistributionPointName OPTIONAL,
onlyContainsUserCerts [1] BOOLEAN DEFAULT FALSE,
onlyContainsCACerts [2] BOOLEAN DEFAULT FALSE,
onlySomeReasons [3] ReasonFlags OPTIONAL,
indirectCRL [4] BOOLEAN DEFAULT FALSE,
onlyContainsAttributeCerts [5] BOOLEAN DEFAULT FALSE }
5.2.6 Freshest CRL (a.k.a. Delta CRL Distribution Point)
The freshest CRL extension identifies how delta CRL information for
this complete CRL is obtained. The extension MUST be non-critical.
This extension MUST NOT appear in delta CRLs.
Housley, et. al. Standards Track [Page 59]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
The same syntax is used for this extension as the
cRLDistributionPoints certificate extension, and is described in
section 4.2.1.14. However, only the distribution point field is
meaningful in this context. The reasons and CRLIssuer fields MUST be
omitted from this CRL extension.
Each distribution point name provides the location at which a delta
CRL for this complete CRL can be found. The scope of these delta
CRLs MUST be the same as the scope of this complete CRL. The
contents of this CRL extension are only used to locate delta CRLs;
the contents are not used to validate the CRL or the referenced delta
CRLs. The encoding conventions defined for distribution points in
section 4.2.1.14 apply to this extension.
id-ce-freshestCRL OBJECT IDENTIFIER ::= { id-ce 46 }
FreshestCRL ::= CRLDistributionPoints
5.3 CRL Entry Extensions
The CRL entry extensions defined by ISO/IEC, ITU-T, and ANSI X9 for
X.509 v2 CRLs provide methods for associating additional attributes
with CRL entries [X.509] [X9.55]. The X.509 v2 CRL format also
allows communities to define private CRL entry extensions to carry
information unique to those communities. Each extension in a CRL
entry may be designated as critical or non-critical. A CRL
validation MUST fail if it encounters a critical CRL entry extension
which it does not know how to process. However, an unrecognized non-
critical CRL entry extension may be ignored. The following
subsections present recommended extensions used within Internet CRL
entries and standard locations for information. Communities may
elect to use additional CRL entry extensions; however, caution should
be exercised in adopting any critical extensions in CRL entries which
might be used in a general context.
All CRL entry extensions used in this specification are non-critical.
Support for these extensions is optional for conforming CRL issuers
and applications. However, CRL issuers SHOULD include reason codes
(section 5.3.1) and invalidity dates (section 5.3.3) whenever this
information is available.
5.3.1 Reason Code
The reasonCode is a non-critical CRL entry extension that identifies
the reason for the certificate revocation. CRL issuers are strongly
encouraged to include meaningful reason codes in CRL entries;
however, the reason code CRL entry extension SHOULD be absent instead
of using the unspecified (0) reasonCode value.
Housley, et. al. Standards Track [Page 60]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
id-ce-cRLReason OBJECT IDENTIFIER ::= { id-ce 21 }
-- reasonCode ::= { CRLReason }
CRLReason ::= ENUMERATED {
unspecified (0),
keyCompromise (1),
cACompromise (2),
affiliationChanged (3),
superseded (4),
cessationOfOperation (5),
certificateHold (6),
removeFromCRL (8),
privilegeWithdrawn (9),
aACompromise (10) }
5.3.2 Hold Instruction Code
The hold instruction code is a non-critical CRL entry extension that
provides a registered instruction identifier which indicates the
action to be taken after encountering a certificate that has been
placed on hold.
id-ce-holdInstructionCode OBJECT IDENTIFIER ::= { id-ce 23 }
holdInstructionCode ::= OBJECT IDENTIFIER
The following instruction codes have been defined. Conforming
applications that process this extension MUST recognize the following
instruction codes.
holdInstruction OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) x9-57(10040) 2 }
id-holdinstruction-none OBJECT IDENTIFIER ::= {holdInstruction 1}
id-holdinstruction-callissuer
OBJECT IDENTIFIER ::= {holdInstruction 2}
id-holdinstruction-reject OBJECT IDENTIFIER ::= {holdInstruction 3}
Conforming applications which encounter an id-holdinstruction-
callissuer MUST call the certificate issuer or reject the
certificate. Conforming applications which encounter an id-
holdinstruction-reject MUST reject the certificate. The hold
instruction id-holdinstruction-none is semantically equivalent to the
absence of a holdInstructionCode, and its use is strongly deprecated
for the Internet PKI.
Housley, et. al. Standards Track [Page 61]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
5.3.3 Invalidity Date
The invalidity date is a non-critical CRL entry extension that
provides the date on which it is known or suspected that the private
key was compromised or that the certificate otherwise became invalid.
This date may be earlier than the revocation date in the CRL entry,
which is the date at which the CA processed the revocation. When a
revocation is first posted by a CRL issuer in a CRL, the invalidity
date may precede the date of issue of earlier CRLs, but the
revocation date SHOULD NOT precede the date of issue of earlier CRLs.
Whenever this information is available, CRL issuers are strongly
encouraged to share it with CRL users.
The GeneralizedTime values included in this field MUST be expressed
in Greenwich Mean Time (Zulu), and MUST be specified and interpreted
as defined in section 4.1.2.5.2.
id-ce-invalidityDate OBJECT IDENTIFIER ::= { id-ce 24 }
invalidityDate ::= GeneralizedTime
5.3.4 Certificate Issuer
This CRL entry extension identifies the certificate issuer associated
with an entry in an indirect CRL, that is, a CRL that has the
indirectCRL indicator set in its issuing distribution point
extension. If this extension is not present on the first entry in an
indirect CRL, the certificate issuer defaults to the CRL issuer. On
subsequent entries in an indirect CRL, if this extension is not
present, the certificate issuer for the entry is the same as that for
the preceding entry. This field is defined as follows:
id-ce-certificateIssuer OBJECT IDENTIFIER ::= { id-ce 29 }
certificateIssuer ::= GeneralNames
If used by conforming CRL issuers, this extension MUST always be
critical. If an implementation ignored this extension it could not
correctly attribute CRL entries to certificates. This specification
RECOMMENDS that implementations recognize this extension.
6 Certification Path Validation
Certification path validation procedures for the Internet PKI are
based on the algorithm supplied in [X.509]. Certification path
processing verifies the binding between the subject distinguished
name and/or subject alternative name and subject public key. The
binding is limited by constraints which are specified in the
Housley, et. al. Standards Track [Page 62]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
certificates which comprise the path and inputs which are specified
by the relying party. The basic constraints and policy constraints
extensions allow the certification path processing logic to automate
the decision making process.
This section describes an algorithm for validating certification
paths. Conforming implementations of this specification are not
required to implement this algorithm, but MUST provide functionality
equivalent to the external behavior resulting from this procedure.
Any algorithm may be used by a particular implementation so long as
it derives the correct result.
In section 6.1, the text describes basic path validation. Valid
paths begin with certificates issued by a trust anchor. The
algorithm requires the public key of the CA, the CA's name, and any
constraints upon the set of paths which may be validated using this
key.
The selection of a trust anchor is a matter of policy: it could be
the top CA in a hierarchical PKI; the CA that issued the verifier's
own certificate(s); or any other CA in a network PKI. The path
validation procedure is the same regardless of the choice of trust
anchor. In addition, different applications may rely on different
trust anchor, or may accept paths that begin with any of a set of
trust anchor.
Section 6.2 describes methods for using the path validation algorithm
in specific implementations. Two specific cases are discussed: the
case where paths may begin with one of several trusted CAs; and where
compatibility with the PEM architecture is required.
Section 6.3 describes the steps necessary to determine if a
certificate is revoked or on hold status when CRLs are the revocation
mechanism used by the certificate issuer.
6.1 Basic Path Validation
This text describes an algorithm for X.509 path processing. A
conformant implementation MUST include an X.509 path processing
procedure that is functionally equivalent to the external behavior of
this algorithm. However, support for some of the certificate
extensions processed in this algorithm are OPTIONAL for compliant
implementations. Clients that do not support these extensions MAY
omit the corresponding steps in the path validation algorithm.
Housley, et. al. Standards Track [Page 63]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
For example, clients are NOT REQUIRED to support the policy mapping
extension. Clients that do not support this extension MAY omit the
path validation steps where policy mappings are processed. Note that
clients MUST reject the certificate if it contains an unsupported
critical extension.
The algorithm presented in this section validates the certificate
with respect to the current date and time. A conformant
implementation MAY also support validation with respect to some point
in the past. Note that mechanisms are not available for validating a
certificate with respect to a time outside the certificate validity
period.
The trust anchor is an input to the algorithm. There is no
requirement that the same trust anchor be used to validate all
certification paths. Different trust anchors MAY be used to validate
different paths, as discussed further in Section 6.2.
The primary goal of path validation is to verify the binding between
a subject distinguished name or a subject alternative name and
subject public key, as represented in the end entity certificate,
based on the public key of the trust anchor. This requires obtaining
a sequence of certificates that support that binding. The procedure
performed to obtain this sequence of certificates is outside the
scope of this specification.
To meet this goal, the path validation process verifies, among other
things, that a prospective certification path (a sequence of n
certificates) satisfies the following conditions:
(a) for all x in {1, ..., n-1}, the subject of certificate x is
the issuer of certificate x+1;
(b) certificate 1 is issued by the trust anchor;
(c) certificate n is the certificate to be validated; and
(d) for all x in {1, ..., n}, the certificate was valid at the
time in question.
When the trust anchor is provided in the form of a self-signed
certificate, this self-signed certificate is not included as part of
the prospective certification path. Information about trust anchors
are provided as inputs to the certification path validation algorithm
(section 6.1.1).
Housley, et. al. Standards Track [Page 64]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
A particular certification path may not, however, be appropriate for
all applications. Therefore, an application MAY augment this
algorithm to further limit the set of valid paths. The path
validation process also determines the set of certificate policies
that are valid for this path, based on the certificate policies
extension, policy mapping extension, policy constraints extension,
and inhibit any-policy extension. To achieve this, the path
validation algorithm constructs a valid policy tree. If the set of
certificate policies that are valid for this path is not empty, then
the result will be a valid policy tree of depth n, otherwise the
result will be a null valid policy tree.
A certificate is self-issued if the DNs that appear in the subject
and issuer fields are identical and are not empty. In general, the
issuer and subject of the certificates that make up a path are
different for each certificate. However, a CA may issue a
certificate to itself to support key rollover or changes in
certificate policies. These self-issued certificates are not counted
when evaluating path length or name constraints.
This section presents the algorithm in four basic steps: (1)
initialization, (2) basic certificate processing, (3) preparation for
the next certificate, and (4) wrap-up. Steps (1) and (4) are
performed exactly once. Step (2) is performed for all certificates
in the path. Step (3) is performed for all certificates in the path
except the final certificate. Figure 2 provides a high-level
flowchart of this algorithm.
Housley, et. al. Standards Track [Page 65]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
+-------+
| START |
+-------+
|
V
+----------------+
| Initialization |
+----------------+
|
+<--------------------+
| |
V |
+----------------+ |
| Process Cert | |
+----------------+ |
| |
V |
+================+ |
| IF Last Cert | |
| in Path | |
+================+ |
| | |
THEN | | ELSE |
V V |
+----------------+ +----------------+ |
| Wrap up | | Prepare for | |
+----------------+ | Next Cert | |
| +----------------+ |
V | |
+-------+ +--------------+
| STOP |
+-------+
Figure 2. Certification Path Processing Flowchart
6.1.1 Inputs
This algorithm assumes the following seven inputs are provided to the
path processing logic:
(a) a prospective certification path of length n.
(b) the current date/time.
Housley, et. al. Standards Track [Page 66]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(c) user-initial-policy-set: A set of certificate policy
identifiers naming the policies that are acceptable to the
certificate user. The user-initial-policy-set contains the
special value any-policy if the user is not concerned about
certificate policy.
(d) trust anchor information, describing a CA that serves as a
trust anchor for the certification path. The trust anchor
information includes:
(1) the trusted issuer name,
(2) the trusted public key algorithm,
(3) the trusted public key, and
(4) optionally, the trusted public key parameters associated
with the public key.
The trust anchor information may be provided to the path
processing procedure in the form of a self-signed certificate.
The trusted anchor information is trusted because it was delivered
to the path processing procedure by some trustworthy out-of-band
procedure. If the trusted public key algorithm requires
parameters, then the parameters are provided along with the
trusted public key.
(e) initial-policy-mapping-inhibit, which indicates if policy
mapping is allowed in the certification path.
(f) initial-explicit-policy, which indicates if the path must be
valid for at least one of the certificate policies in the user-
initial-policy-set.
(g) initial-any-policy-inhibit, which indicates whether the
anyPolicy OID should be processed if it is included in a
certificate.
6.1.2 Initialization
This initialization phase establishes eleven state variables based
upon the seven inputs:
(a) valid_policy_tree: A tree of certificate policies with their
optional qualifiers; each of the leaves of the tree represents a
valid policy at this stage in the certification path validation.
If valid policies exist at this stage in the certification path
validation, the depth of the tree is equal to the number of
Housley, et. al. Standards Track [Page 67]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
certificates in the chain that have been processed. If valid
policies do not exist at this stage in the certification path
validation, the tree is set to NULL. Once the tree is set to
NULL, policy processing ceases.
Each node in the valid_policy_tree includes four data objects: the
valid policy, a set of associated policy qualifiers, a set of one
or more expected policy values, and a criticality indicator. If
the node is at depth x, the components of the node have the
following semantics:
(1) The valid_policy is a single policy OID representing a
valid policy for the path of length x.
(2) The qualifier_set is a set of policy qualifiers associated
with the valid policy in certificate x.
(3) The criticality_indicator indicates whether the
certificate policy extension in certificate x was marked as
critical.
(4) The expected_policy_set contains one or more policy OIDs
that would satisfy this policy in the certificate x+1.
The initial value of the valid_policy_tree is a single node with
valid_policy anyPolicy, an empty qualifier_set, an
expected_policy_set with the single value anyPolicy, and a
criticality_indicator of FALSE. This node is considered to be at
depth zero.
Figure 3 is a graphic representation of the initial state of the
valid_policy_tree. Additional figures will use this format to
describe changes in the valid_policy_tree during path processing.
+----------------+
| anyPolicy | <---- valid_policy
+----------------+
| {} | <---- qualifier_set
+----------------+
| FALSE | <---- criticality_indicator
+----------------+
| {anyPolicy} | <---- expected_policy_set
+----------------+
Figure 3. Initial value of the valid_policy_tree state variable
Housley, et. al. Standards Track [Page 68]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(b) permitted_subtrees: A set of root names for each name type
(e.g., X.500 distinguished names, email addresses, or ip
addresses) defining a set of subtrees within which all subject
names in subsequent certificates in the certification path MUST
fall. This variable includes a set for each name type: the
initial value for the set for Distinguished Names is the set of
all Distinguished names; the initial value for the set of RFC822
names is the set of all RFC822 names, etc.
(c) excluded_subtrees: A set of root names for each name type
(e.g., X.500 distinguished names, email addresses, or ip
addresses) defining a set of subtrees within which no subject name
in subsequent certificates in the certification path may fall.
This variable includes a set for each name type, and the initial
value for each set is empty.
(d) explicit_policy: an integer which indicates if a non-NULL
valid_policy_tree is required. The integer indicates the number of
non-self-issued certificates to be processed before this
requirement is imposed. Once set, this variable may be decreased,
but may not be increased. That is, if a certificate in the path
requires a non-NULL valid_policy_tree, a later certificate can not
remove this requirement. If initial-explicit-policy is set, then
the initial value is 0, otherwise the initial value is n+1.
(e) inhibit_any-policy: an integer which indicates whether the
anyPolicy policy identifier is considered a match. The integer
indicates the number of non-self-issued certificates to be
processed before the anyPolicy OID, if asserted in a certificate,
is ignored. Once set, this variable may be decreased, but may not
be increased. That is, if a certificate in the path inhibits
processing of anyPolicy, a later certificate can not permit it.
If initial-any-policy-inhibit is set, then the initial value is 0,
otherwise the initial value is n+1.
(f) policy_mapping: an integer which indicates if policy mapping
is permitted. The integer indicates the number of non-self-issued
certificates to be processed before policy mapping is inhibited.
Once set, this variable may be decreased, but may not be
increased. That is, if a certificate in the path specifies policy
mapping is not permitted, it can not be overridden by a later
certificate. If initial-policy-mapping-inhibit is set, then the
initial value is 0, otherwise the initial value is n+1.
(g) working_public_key_algorithm: the digital signature algorithm
used to verify the signature of a certificate. The
working_public_key_algorithm is initialized from the trusted
public key algorithm provided in the trust anchor information.
Housley, et. al. Standards Track [Page 69]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(h) working_public_key: the public key used to verify the
signature of a certificate. The working_public_key is initialized
from the trusted public key provided in the trust anchor
information.
(i) working_public_key_parameters: parameters associated with the
current public key, that may be required to verify a signature
(depending upon the algorithm). The working_public_key_parameters
variable is initialized from the trusted public key parameters
provided in the trust anchor information.
(j) working_issuer_name: the issuer distinguished name expected
in the next certificate in the chain. The working_issuer_name is
initialized to the trusted issuer provided in the trust anchor
information.
(k) max_path_length: this integer is initialized to n, is
decremented for each non-self-issued certificate in the path, and
may be reduced to the value in the path length constraint field
within the basic constraints extension of a CA certificate.
Upon completion of the initialization steps, perform the basic
certificate processing steps specified in 6.1.3.
6.1.3 Basic Certificate Processing
The basic path processing actions to be performed for certificate i
(for all i in [1..n]) are listed below.
(a) Verify the basic certificate information. The certificate
MUST satisfy each of the following:
(1) The certificate was signed with the
working_public_key_algorithm using the working_public_key and
the working_public_key_parameters.
(2) The certificate validity period includes the current time.
(3) At the current time, the certificate is not revoked and is
not on hold status. This may be determined by obtaining the
appropriate CRL (section 6.3), status information, or by out-
of-band mechanisms.
(4) The certificate issuer name is the working_issuer_name.
Housley, et. al. Standards Track [Page 70]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(b) If certificate i is self-issued and it is not the final
certificate in the path, skip this step for certificate i.
Otherwise, verify that the subject name is within one of the
permitted_subtrees for X.500 distinguished names, and verify that
each of the alternative names in the subjectAltName extension
(critical or non-critical) is within one of the permitted_subtrees
for that name type.
(c) If certificate i is self-issued and it is not the final
certificate in the path, skip this step for certificate i.
Otherwise, verify that the subject name is not within one of the
excluded_subtrees for X.500 distinguished names, and verify that
each of the alternative names in the subjectAltName extension
(critical or non-critical) is not within one of the
excluded_subtrees for that name type.
(d) If the certificate policies extension is present in the
certificate and the valid_policy_tree is not NULL, process the
policy information by performing the following steps in order:
(1) For each policy P not equal to anyPolicy in the
certificate policies extension, let P-OID denote the OID in
policy P and P-Q denote the qualifier set for policy P.
Perform the following steps in order:
(i) If the valid_policy_tree includes a node of depth i-1
where P-OID is in the expected_policy_set, create a child
node as follows: set the valid_policy to OID-P; set the
qualifier_set to P-Q, and set the expected_policy_set to
{P-OID}.
For example, consider a valid_policy_tree with a node of
depth i-1 where the expected_policy_set is {Gold, White}.
Assume the certificate policies Gold and Silver appear in
the certificate policies extension of certificate i. The
Gold policy is matched but the Silver policy is not. This
rule will generate a child node of depth i for the Gold
policy. The result is shown as Figure 4.
Housley, et. al. Standards Track [Page 71]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
+-----------------+
| Red |
+-----------------+
| {} |
+-----------------+ node of depth i-1
| FALSE |
+-----------------+
| {Gold, White} |
+-----------------+
|
|
|
V
+-----------------+
| Gold |
+-----------------+
| {} |
+-----------------+ node of depth i
| uninitialized |
+-----------------+
| {Gold} |
+-----------------+
Figure 4. Processing an exact match
(ii) If there was no match in step (i) and the
valid_policy_tree includes a node of depth i-1 with the
valid policy anyPolicy, generate a child node with the
following values: set the valid_policy to P-OID; set the
qualifier_set to P-Q, and set the expected_policy_set to
{P-OID}.
For example, consider a valid_policy_tree with a node of
depth i-1 where the valid_policy is anyPolicy. Assume the
certificate policies Gold and Silver appear in the
certificate policies extension of certificate i. The Gold
policy does not have a qualifier, but the Silver policy has
the qualifier Q-Silver. If Gold and Silver were not matched
in (i) above, this rule will generate two child nodes of
depth i, one for each policy. The result is shown as Figure
5.
Housley, et. al. Standards Track [Page 72]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
+-----------------+
| anyPolicy |
+-----------------+
| {} |
+-----------------+ node of depth i-1
| FALSE |
+-----------------+
| {anyPolicy} |
+-----------------+
/ \
/ \
/ \
/ \
+-----------------+ +-----------------+
| Gold | | Silver |
+-----------------+ +-----------------+
| {} | | {Q-Silver} |
+-----------------+ nodes of +-----------------+
| uninitialized | depth i | uninitialized |
+-----------------+ +-----------------+
| {Gold} | | {Silver} |
+-----------------+ +-----------------+
Figure 5. Processing unmatched policies when a leaf node
specifies anyPolicy
(2) If the certificate policies extension includes the policy
anyPolicy with the qualifier set AP-Q and either (a)
inhibit_any-policy is greater than 0 or (b) i<n and the
certificate is self-issued, then:
For each node in the valid_policy_tree of depth i-1, for each
value in the expected_policy_set (including anyPolicy) that
does not appear in a child node, create a child node with the
following values: set the valid_policy to the value from the
expected_policy_set in the parent node; set the qualifier_set
to AP-Q, and set the expected_policy_set to the value in the
valid_policy from this node.
For example, consider a valid_policy_tree with a node of depth
i-1 where the expected_policy_set is {Gold, Silver}. Assume
anyPolicy appears in the certificate policies extension of
certificate i, but Gold and Silver do not. This rule will
generate two child nodes of depth i, one for each policy. The
result is shown below as Figure 6.
Housley, et. al. Standards Track [Page 73]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
+-----------------+
| Red |
+-----------------+
| {} |
+-----------------+ node of depth i-1
| FALSE |
+-----------------+
| {Gold, Silver} |
+-----------------+
/ \
/ \
/ \
/ \
+-----------------+ +-----------------+
| Gold | | Silver |
+-----------------+ +-----------------+
| {} | | {} |
+-----------------+ nodes of +-----------------+
| uninitialized | depth i | uninitialized |
+-----------------+ +-----------------+
| {Gold} | | {Silver} |
+-----------------+ +-----------------+
Figure 6. Processing unmatched policies when the certificate
policies extension specifies anyPolicy
(3) If there is a node in the valid_policy_tree of depth i-1
or less without any child nodes, delete that node. Repeat this
step until there are no nodes of depth i-1 or less without
children.
For example, consider the valid_policy_tree shown in Figure 7
below. The two nodes at depth i-1 that are marked with an 'X'
have no children, and are deleted. Applying this rule to the
resulting tree will cause the node at depth i-2 that is marked
with an 'Y' to be deleted. The following application of the
rule does not cause any nodes to be deleted, and this step is
complete.
Housley, et. al. Standards Track [Page 74]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
+-----------+
| | node of depth i-3
+-----------+
/ | \
/ | \
/ | \
+-----------+ +-----------+ +-----------+
| | | | | Y | nodes of
+-----------+ +-----------+ +-----------+ depth i-2
/ \ | |
/ \ | |
/ \ | |
+-----------+ +-----------+ +-----------+ +-----------+ nodes of
| | | X | | | | X | depth
+-----------+ +-----------+ +-----------+ +-----------+ i-1
| / | \
| / | \
| / | \
+-----------+ +-----------+ +-----------+ +-----------+ nodes of
| | | | | | | | depth
+-----------+ +-----------+ +-----------+ +-----------+ i
Figure 7. Pruning the valid_policy_tree
(4) If the certificate policies extension was marked as
critical, set the criticality_indicator in all nodes of depth i
to TRUE. If the certificate policies extension was not marked
critical, set the criticality_indicator in all nodes of depth i
to FALSE.
(e) If the certificate policies extension is not present, set the
valid_policy_tree to NULL.
(f) Verify that either explicit_policy is greater than 0 or the
valid_policy_tree is not equal to NULL;
If any of steps (a), (b), (c), or (f) fails, the procedure
terminates, returning a failure indication and an appropriate reason.
If i is not equal to n, continue by performing the preparatory steps
listed in 6.1.4. If i is equal to n, perform the wrap-up steps
listed in 6.1.5.
6.1.4 Preparation for Certificate i+1
To prepare for processing of certificate i+1, perform the following
steps for certificate i:
Housley, et. al. Standards Track [Page 75]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(a) If a policy mapping extension is present, verify that the
special value anyPolicy does not appear as an issuerDomainPolicy
or a subjectDomainPolicy.
(b) If a policy mapping extension is present, then for each
issuerDomainPolicy ID-P in the policy mapping extension:
(1) If the policy_mapping variable is greater than 0, for each
node in the valid_policy_tree of depth i where ID-P is the
valid_policy, set expected_policy_set to the set of
subjectDomainPolicy values that are specified as equivalent to
ID-P by the policy mapping extension.
If no node of depth i in the valid_policy_tree has a
valid_policy of ID-P but there is a node of depth i with a
valid_policy of anyPolicy, then generate a child node of the
node of depth i-1 that has a valid_policy of anyPolicy as
follows:
(i) set the valid_policy to ID-P;
(ii) set the qualifier_set to the qualifier set of the
policy anyPolicy in the certificate policies extension of
certificate i;
(iii) set the criticality_indicator to the criticality of
the certificate policies extension of certificate i;
(iv) and set the expected_policy_set to the set of
subjectDomainPolicy values that are specified as equivalent
to ID-P by the policy mappings extension.
(2) If the policy_mapping variable is equal to 0:
(i) delete each node of depth i in the valid_policy_tree
where ID-P is the valid_policy.
(ii) If there is a node in the valid_policy_tree of depth
i-1 or less without any child nodes, delete that node.
Repeat this step until there are no nodes of depth i-1 or
less without children.
(c) Assign the certificate subject name to working_issuer_name.
(d) Assign the certificate subjectPublicKey to
working_public_key.
Housley, et. al. Standards Track [Page 76]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(e) If the subjectPublicKeyInfo field of the certificate contains
an algorithm field with non-null parameters, assign the parameters
to the working_public_key_parameters variable.
If the subjectPublicKeyInfo field of the certificate contains an
algorithm field with null parameters or parameters are omitted,
compare the certificate subjectPublicKey algorithm to the
working_public_key_algorithm. If the certificate subjectPublicKey
algorithm and the working_public_key_algorithm are different, set
the working_public_key_parameters to null.
(f) Assign the certificate subjectPublicKey algorithm to the
working_public_key_algorithm variable.
(g) If a name constraints extension is included in the
certificate, modify the permitted_subtrees and excluded_subtrees
state variables as follows:
(1) If permittedSubtrees is present in the certificate, set
the permitted_subtrees state variable to the intersection of
its previous value and the value indicated in the extension
field. If permittedSubtrees does not include a particular name
type, the permitted_subtrees state variable is unchanged for
that name type. For example, the intersection of nist.gov and
csrc.nist.gov is csrc.nist.gov. And, the intersection of
nist.gov and rsasecurity.com is the empty set.
(2) If excludedSubtrees is present in the certificate, set the
excluded_subtrees state variable to the union of its previous
value and the value indicated in the extension field. If
excludedSubtrees does not include a particular name type, the
excluded_subtrees state variable is unchanged for that name
type. For example, the union of the name spaces nist.gov and
csrc.nist.gov is nist.gov. And, the union of nist.gov and
rsasecurity.com is both name spaces.
(h) If the issuer and subject names are not identical:
(1) If explicit_policy is not 0, decrement explicit_policy by
1.
(2) If policy_mapping is not 0, decrement policy_mapping by 1.
(3) If inhibit_any-policy is not 0, decrement inhibit_any-
policy by 1.
Housley, et. al. Standards Track [Page 77]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(i) If a policy constraints extension is included in the
certificate, modify the explicit_policy and policy_mapping state
variables as follows:
(1) If requireExplicitPolicy is present and is less than
explicit_policy, set explicit_policy to the value of
requireExplicitPolicy.
(2) If inhibitPolicyMapping is present and is less than
policy_mapping, set policy_mapping to the value of
inhibitPolicyMapping.
(j) If the inhibitAnyPolicy extension is included in the
certificate and is less than inhibit_any-policy, set inhibit_any-
policy to the value of inhibitAnyPolicy.
(k) Verify that the certificate is a CA certificate (as specified
in a basicConstraints extension or as verified out-of-band).
(l) If the certificate was not self-issued, verify that
max_path_length is greater than zero and decrement max_path_length
by 1.
(m) If pathLengthConstraint is present in the certificate and is
less than max_path_length, set max_path_length to the value of
pathLengthConstraint.
(n) If a key usage extension is present, verify that the
keyCertSign bit is set.
(o) Recognize and process any other critical extension present in
the certificate. Process any other recognized non-critical
extension present in the certificate.
If check (a), (k), (l), (n) or (o) fails, the procedure terminates,
returning a failure indication and an appropriate reason.
If (a), (k), (l), (n) and (o) have completed successfully, increment
i and perform the basic certificate processing specified in 6.1.3.
6.1.5 Wrap-up procedure
To complete the processing of the end entity certificate, perform the
following steps for certificate n:
(a) If certificate n was not self-issued and explicit_policy is
not 0, decrement explicit_policy by 1.
Housley, et. al. Standards Track [Page 78]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(b) If a policy constraints extension is included in the
certificate and requireExplicitPolicy is present and has a value
of 0, set the explicit_policy state variable to 0.
(c) Assign the certificate subjectPublicKey to
working_public_key.
(d) If the subjectPublicKeyInfo field of the certificate contains
an algorithm field with non-null parameters, assign the parameters
to the working_public_key_parameters variable.
If the subjectPublicKeyInfo field of the certificate contains an
algorithm field with null parameters or parameters are omitted,
compare the certificate subjectPublicKey algorithm to the
working_public_key_algorithm. If the certificate subjectPublicKey
algorithm and the working_public_key_algorithm are different, set
the working_public_key_parameters to null.
(e) Assign the certificate subjectPublicKey algorithm to the
working_public_key_algorithm variable.
(f) Recognize and process any other critical extension present in
the certificate n. Process any other recognized non-critical
extension present in certificate n.
(g) Calculate the intersection of the valid_policy_tree and the
user-initial-policy-set, as follows:
(i) If the valid_policy_tree is NULL, the intersection is
NULL.
(ii) If the valid_policy_tree is not NULL and the user-
initial-policy-set is any-policy, the intersection is the
entire valid_policy_tree.
(iii) If the valid_policy_tree is not NULL and the user-
initial-policy-set is not any-policy, calculate the
intersection of the valid_policy_tree and the user-initial-
policy-set as follows:
1. Determine the set of policy nodes whose parent nodes
have a valid_policy of anyPolicy. This is the
valid_policy_node_set.
2. If the valid_policy of any node in the
valid_policy_node_set is not in the user-initial-policy-set
and is not anyPolicy, delete this node and all its children.
Housley, et. al. Standards Track [Page 79]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
3. If the valid_policy_tree includes a node of depth n with
the valid_policy anyPolicy and the user-initial-policy-set
is not any-policy perform the following steps:
a. Set P-Q to the qualifier_set in the node of depth n
with valid_policy anyPolicy.
b. For each P-OID in the user-initial-policy-set that is
not the valid_policy of a node in the
valid_policy_node_set, create a child node whose parent
is the node of depth n-1 with the valid_policy anyPolicy.
Set the values in the child node as follows: set the
valid_policy to P-OID; set the qualifier_set to P-Q; copy
the criticality_indicator from the node of depth n with
the valid_policy anyPolicy; and set the
expected_policy_set to {P-OID}.
c. Delete the node of depth n with the valid_policy
anyPolicy.
4. If there is a node in the valid_policy_tree of depth n-1
or less without any child nodes, delete that node. Repeat
this step until there are no nodes of depth n-1 or less
without children.
If either (1) the value of explicit_policy variable is greater than
zero, or (2) the valid_policy_tree is not NULL, then path processing
has succeeded.
6.1.6 Outputs
If path processing succeeds, the procedure terminates, returning a
success indication together with final value of the
valid_policy_tree, the working_public_key, the
working_public_key_algorithm, and the working_public_key_parameters.
6.2 Using the Path Validation Algorithm
The path validation algorithm describes the process of validating a
single certification path. While each certification path begins with
a specific trust anchor, there is no requirement that all
certification paths validated by a particular system share a single
trust anchor. An implementation that supports multiple trust anchors
MAY augment the algorithm presented in section 6.1 to further limit
the set of valid certification paths which begin with a particular
trust anchor. For example, an implementation MAY modify the
algorithm to apply name constraints to a specific trust anchor during
the initialization phase, or the application MAY require the presence
Housley, et. al. Standards Track [Page 80]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
of a particular alternative name form in the end entity certificate,
or the application MAY impose requirements on application-specific
extensions. Thus, the path validation algorithm presented in section
6.1 defines the minimum conditions for a path to be considered valid.
The selection of one or more trusted CAs is a local decision. A
system may provide any one of its trusted CAs as the trust anchor for
a particular path. The inputs to the path validation algorithm may
be different for each path. The inputs used to process a path may
reflect application-specific requirements or limitations in the trust
accorded a particular trust anchor. For example, a trusted CA may
only be trusted for a particular certificate policy. This
restriction can be expressed through the inputs to the path
validation procedure.
It is also possible to specify an extended version of the above
certification path processing procedure which results in default
behavior identical to the rules of PEM [RFC 1422]. In this extended
version, additional inputs to the procedure are a list of one or more
Policy Certification Authority (PCA) names and an indicator of the
position in the certification path where the PCA is expected. At the
nominated PCA position, the CA name is compared against this list.
If a recognized PCA name is found, then a constraint of
SubordinateToCA is implicitly assumed for the remainder of the
certification path and processing continues. If no valid PCA name is
found, and if the certification path cannot be validated on the basis
of identified policies, then the certification path is considered
invalid.
6.3 CRL Validation
This section describes the steps necessary to determine if a
certificate is revoked or on hold status when CRLs are the revocation
mechanism used by the certificate issuer. Conforming implementations
that support CRLs are not required to implement this algorithm, but
they MUST be functionally equivalent to the external behavior
resulting from this procedure. Any algorithm may be used by a
particular implementation so long as it derives the correct result.
This algorithm assumes that all of the needed CRLs are available in a
local cache. Further, if the next update time of a CRL has passed,
the algorithm assumes a mechanism to fetch a current CRL and place it
in the local CRL cache.
This algorithm defines a set of inputs, a set of state variables, and
processing steps that are performed for each certificate in the path.
The algorithm output is the revocation status of the certificate.
Housley, et. al. Standards Track [Page 81]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
6.3.1 Revocation Inputs
To support revocation processing, the algorithm requires two inputs:
(a) certificate: The algorithm requires the certificate serial
number and issuer name to determine whether a certificate is on a
particular CRL. The basicConstraints extension is used to
determine whether the supplied certificate is associated with a CA
or an end entity. If present, the algorithm uses the
cRLDistributionsPoint and freshestCRL extensions to determine
revocation status.
(b) use-deltas: This boolean input determines whether delta CRLs
are applied to CRLs.
Note that implementations supporting legacy PKIs, such as RFC 1422
and X.509 version 1, will need an additional input indicating
whether the supplied certificate is associated with a CA or an end
entity.
6.3.2 Initialization and Revocation State Variables
To support CRL processing, the algorithm requires the following state
variables:
(a) reasons_mask: This variable contains the set of revocation
reasons supported by the CRLs and delta CRLs processed so far.
The legal members of the set are the possible revocation reason
values: unspecified, keyCompromise, caCompromise,
affiliationChanged, superseded, cessationOfOperation,
certificateHold, privilegeWithdrawn, and aACompromise. The
special value all-reasons is used to denote the set of all legal
members. This variable is initialized to the empty set.
(b) cert_status: This variable contains the status of the
certificate. This variable may be assigned one of the following
values: unspecified, keyCompromise, caCompromise,
affiliationChanged, superseded, cessationOfOperation,
certificateHold, removeFromCRL, privilegeWithdrawn, aACompromise,
the special value UNREVOKED, or the special value UNDETERMINED.
This variable is initialized to the special value UNREVOKED.
(c) interim_reasons_mask: This contains the set of revocation
reasons supported by the CRL or delta CRL currently being
processed.
Housley, et. al. Standards Track [Page 82]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
Note: In some environments, it is not necessary to check all reason
codes. For example, some environments are only concerned with
caCompromise and keyCompromise for CA certificates. This algorithm
checks all reason codes. Additional processing and state variables
may be necessary to limit the checking to a subset of the reason
codes.
6.3.3 CRL Processing
This algorithm begins by assuming the certificate is not revoked.
The algorithm checks one or more CRLs until either the certificate
status is determined to be revoked or sufficient CRLs have been
checked to cover all reason codes.
For each distribution point (DP) in the certificate CRL distribution
points extension, for each corresponding CRL in the local CRL cache,
while ((reasons_mask is not all-reasons) and (cert_status is
UNREVOKED)) perform the following:
(a) Update the local CRL cache by obtaining a complete CRL, a
delta CRL, or both, as required:
(1) If the current time is after the value of the CRL next
update field, then do one of the following:
(i) If use-deltas is set and either the certificate or the
CRL contains the freshest CRL extension, obtain a delta CRL
with the a next update value that is after the current time
and can be used to update the locally cached CRL as
specified in section 5.2.4.
(ii) Update the local CRL cache with a current complete
CRL, verify that the current time is before the next update
value in the new CRL, and continue processing with the new
CRL. If use-deltas is set, then obtain the current delta
CRL that can be used to update the new locally cached
complete CRL as specified in section 5.2.4.
(2) If the current time is before the value of the next update
field and use-deltas is set, then obtain the current delta CRL
that can be used to update the locally cached complete CRL as
specified in section 5.2.4.
(b) Verify the issuer and scope of the complete CRL as follows:
Housley, et. al. Standards Track [Page 83]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(1) If the DP includes cRLIssuer, then verify that the issuer
field in the complete CRL matches cRLIssuer in the DP and that
the complete CRL contains an issuing distribution point
extension with the indrectCRL boolean asserted. Otherwise,
verify that the CRL issuer matches the certificate issuer.
(2) If the complete CRL includes an issuing distribution point
(IDP) CRL extension check the following:
(i) If the distribution point name is present in the IDP
CRL extension and the distribution field is present in the
DP, then verify that one of the names in the IDP matches one
of the names in the DP. If the distribution point name is
present in the IDP CRL extension and the distribution field
is omitted from the DP, then verify that one of the names in
the IDP matches one of the names in the cRLIssuer field of
the DP.
(ii) If the onlyContainsUserCerts boolean is asserted in
the IDP CRL extension, verify that the certificate does not
include the basic constraints extension with the cA boolean
asserted.
(iii) If the onlyContainsCACerts boolean is asserted in the
IDP CRL extension, verify that the certificate includes the
basic constraints extension with the cA boolean asserted.
(iv) Verify that the onlyContainsAttributeCerts boolean is
not asserted.
(c) If use-deltas is set, verify the issuer and scope of the
delta CRL as follows:
(1) Verify that the delta CRL issuer matches complete CRL
issuer.
(2) If the complete CRL includes an issuing distribution point
(IDP) CRL extension, verify that the delta CRL contains a
matching IDP CRL extension. If the complete CRL omits an IDP
CRL extension, verify that the delta CRL also omits an IDP CRL
extension.
(3) Verify that the delta CRL authority key identifier
extension matches complete CRL authority key identifier
extension.
Housley, et. al. Standards Track [Page 84]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(d) Compute the interim_reasons_mask for this CRL as follows:
(1) If the issuing distribution point (IDP) CRL extension is
present and includes onlySomeReasons and the DP includes
reasons, then set interim_reasons_mask to the intersection of
reasons in the DP and onlySomeReasons in IDP CRL extension.
(2) If the IDP CRL extension includes onlySomeReasons but the
DP omits reasons, then set interim_reasons_mask to the value of
onlySomeReasons in IDP CRL extension.
(3) If the IDP CRL extension is not present or omits
onlySomeReasons but the DP includes reasons, then set
interim_reasons_mask to the value of DP reasons.
(4) If the IDP CRL extension is not present or omits
onlySomeReasons and the DP omits reasons, then set
interim_reasons_mask to the special value all-reasons.
(e) Verify that interim_reasons_mask includes one or more reasons
that is not included in the reasons_mask.
(f) Obtain and validate the certification path for the complete CRL
issuer. If a key usage extension is present in the CRL issuer's
certificate, verify that the cRLSign bit is set.
(g) Validate the signature on the complete CRL using the public key
validated in step (f).
(h) If use-deltas is set, then validate the signature on the delta
CRL using the public key validated in step (f).
(i) If use-deltas is set, then search for the certificate on the
delta CRL. If an entry is found that matches the certificate issuer
and serial number as described in section 5.3.4, then set the
cert_status variable to the indicated reason as follows:
(1) If the reason code CRL entry extension is present, set the
cert_status variable to the value of the reason code CRL entry
extension.
(2) If the reason code CRL entry extension is not present, set
the cert_status variable to the value unspecified.
Housley, et. al. Standards Track [Page 85]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(j) If (cert_status is UNREVOKED), then search for the
certificate on the complete CRL. If an entry is found that
matches the certificate issuer and serial number as described in
section 5.3.4, then set the cert_status variable to the indicated
reason as described in step (i).
(k) If (cert_status is removeFromCRL), then set cert_status to
UNREVOKED.
If ((reasons_mask is all-reasons) OR (cert_status is not UNREVOKED)),
then the revocation status has been determined, so return
cert_status.
If the revocation status has not been determined, repeat the process
above with any available CRLs not specified in a distribution point
but issued by the certificate issuer. For the processing of such a
CRL, assume a DP with both the reasons and the cRLIssuer fields
omitted and a distribution point name of the certificate issuer.
That is, the sequence of names in fullName is generated from the
certificate issuer field as well as the certificate issuerAltName
extension. If the revocation status remains undetermined, then
return the cert_status UNDETERMINED.
7 References
[ISO 10646] ISO/IEC 10646-1:1993. International Standard --
Information technology -- Universal Multiple-Octet Coded
Character Set (UCS) -- Part 1: Architecture and Basic
Multilingual Plane.
[RFC 791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC 822] Crocker, D., "Standard for the format of ARPA Internet
text messages", STD 11, RFC 822, August 1982.
[RFC 1034] Mockapetris, P., "Domain Names - Concepts and
Facilities", STD 13, RFC 1034, November 1987.
[RFC 1422] Kent, S., "Privacy Enhancement for Internet Electronic
Mail: Part II: Certificate-Based Key Management," RFC
1422, February 1993.
[RFC 1423] Balenson, D., "Privacy Enhancement for Internet
Electronic Mail: Part III: Algorithms, Modes, and
Identifiers," RFC 1423, February 1993.
Housley, et. al. Standards Track [Page 86]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
[RFC 1510] Kohl, J. and C. Neuman, "The Kerberos Network
Authentication Service (V5)," RFC 1510, September 1993.
[RFC 1519] Fuller, V., T. Li, J. Yu and K. Varadhan, "Classless
Inter-Domain Routing (CIDR): An Address Assignment and
Aggregation Strategy", RFC 1519, September 1993.
[RFC 1738] Berners-Lee, T., L. Masinter and M. McCahill, "Uniform
Resource Locators (URL)", RFC 1738, December 1994.
[RFC 1778] Howes, T., S. Kille, W. Yeong and C. Robbins, "The String
Representation of Standard Attribute Syntaxes," RFC 1778,
March 1995.
[RFC 1883] Deering, S. and R. Hinden. "Internet Protocol, Version 6
(IPv6) Specification", RFC 1883, December 1995.
[RFC 2044] F. Yergeau, F., "UTF-8, a transformation format of
Unicode and ISO 10646", RFC 2044, October 1996.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 2247] Kille, S., M. Wahl, A. Grimstad, R. Huber and S.
Sataluri, "Using Domains in LDAP/X.500 Distinguished
Names", RFC 2247, January 1998.
[RFC 2252] Wahl, M., A. Coulbeck, T. Howes and S. Kille,
"Lightweight Directory Access Protocol (v3): Attribute
Syntax Definitions", RFC 2252, December 1997.
[RFC 2277] Alvestrand, H., "IETF Policy on Character Sets and
Languages", BCP 18, RFC 2277, January 1998.
[RFC 2279] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 2279, January 1998.
[RFC 2459] Housley, R., W. Ford, W. Polk and D. Solo, "Internet
X.509 Public Key Infrastructure: Certificate and CRL
Profile", RFC 2459, January 1999.
[RFC 2560] Myers, M., R. Ankney, A. Malpani, S. Galperin and C.
Adams, "Online Certificate Status Protocal - OCSP", June
1999.
[SDN.701] SDN.701, "Message Security Protocol 4.0", Revision A,
1997-02-06.
Housley, et. al. Standards Track [Page 87]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
[X.501] ITU-T Recommendation X.501: Information Technology - Open
Systems Interconnection - The Directory: Models, 1993.
[X.509] ITU-T Recommendation X.509 (1997 E): Information
Technology - Open Systems Interconnection - The
Directory: Authentication Framework, June 1997.
[X.520] ITU-T Recommendation X.520: Information Technology - Open
Systems Interconnection - The Directory: Selected
Attribute Types, 1993.
[X.660] ITU-T Recommendation X.660 Information Technology - ASN.1
encoding rules: Specification of Basic Encoding Rules
(BER), Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER), 1997.
[X.690] ITU-T Recommendation X.690 Information Technology - Open
Systems Interconnection - Procedures for the operation of
OSI Registration Authorities: General procedures, 1992.
[X9.55] ANSI X9.55-1995, Public Key Cryptography For The
Financial Services Industry: Extensions To Public Key
Certificates And Certificate Revocation Lists, 8
December, 1995.
[PKIXALGS] Bassham, L., Polk, W. and R. Housley, "Algorithms and
Identifiers for the Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation
Lists (CRL) Profile", RFC 3279, April 2002.
[PKIXTSA] Adams, C., Cain, P., Pinkas, D. and R. Zuccherato,
"Internet X.509 Public Key Infrastructure Time-Stamp
Protocol (TSP)", RFC 3161, August 2001.
8 Intellectual Property Rights
The IETF has been notified of intellectual property rights claimed in
regard to some or all of the specification contained in this
document. For more information consult the online list of claimed
rights (see http://www.ietf.org/ipr.html).
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
Housley, et. al. Standards Track [Page 88]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
standards-related documentation can be found in BCP 11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
9 Security Considerations
The majority of this specification is devoted to the format and
content of certificates and CRLs. Since certificates and CRLs are
digitally signed, no additional integrity service is necessary.
Neither certificates nor CRLs need be kept secret, and unrestricted
and anonymous access to certificates and CRLs has no security
implications.
However, security factors outside the scope of this specification
will affect the assurance provided to certificate users. This
section highlights critical issues to be considered by implementers,
administrators, and users.
The procedures performed by CAs and RAs to validate the binding of
the subject's identity to their public key greatly affect the
assurance that ought to be placed in the certificate. Relying
parties might wish to review the CA's certificate practice statement.
This is particularly important when issuing certificates to other
CAs.
The use of a single key pair for both signature and other purposes is
strongly discouraged. Use of separate key pairs for signature and
key management provides several benefits to the users. The
ramifications associated with loss or disclosure of a signature key
are different from loss or disclosure of a key management key. Using
separate key pairs permits a balanced and flexible response.
Similarly, different validity periods or key lengths for each key
pair may be appropriate in some application environments.
Unfortunately, some legacy applications (e.g., SSL) use a single key
pair for signature and key management.
The protection afforded private keys is a critical security factor.
On a small scale, failure of users to protect their private keys will
permit an attacker to masquerade as them, or decrypt their personal
information. On a larger scale, compromise of a CA's private signing
key may have a catastrophic effect. If an attacker obtains the
private key unnoticed, the attacker may issue bogus certificates and
CRLs. Existence of bogus certificates and CRLs will undermine
confidence in the system. If such a compromise is detected, all
certificates issued to the compromised CA MUST be revoked, preventing
Housley, et. al. Standards Track [Page 89]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
services between its users and users of other CAs. Rebuilding after
such a compromise will be problematic, so CAs are advised to
implement a combination of strong technical measures (e.g., tamper-
resistant cryptographic modules) and appropriate management
procedures (e.g., separation of duties) to avoid such an incident.
Loss of a CA's private signing key may also be problematic. The CA
would not be able to produce CRLs or perform normal key rollover.
CAs SHOULD maintain secure backup for signing keys. The security of
the key backup procedures is a critical factor in avoiding key
compromise.
The availability and freshness of revocation information affects the
degree of assurance that ought to be placed in a certificate. While
certificates expire naturally, events may occur during its natural
lifetime which negate the binding between the subject and public key.
If revocation information is untimely or unavailable, the assurance
associated with the binding is clearly reduced. Relying parties
might not be able to process every critical extension that can appear
in a CRL. CAs SHOULD take extra care when making revocation
information available only through CRLs that contain critical
extensions, particularly if support for those extensions is not
mandated by this profile. For example, if revocation information is
supplied using a combination of delta CRLs and full CRLs, and the
delta CRLs are issued more frequently than the full CRLs, then
relying parties that cannot handle the critical extensions related to
delta CRL processing will not be able to obtain the most recent
revocation information. Alternatively, if a full CRL is issued
whenever a delta CRL is issued, then timely revocation information
will be available to all relying parties. Similarly, implementations
of the certification path validation mechanism described in section 6
that omit revocation checking provide less assurance than those that
support it.
The certification path validation algorithm depends on the certain
knowledge of the public keys (and other information) about one or
more trusted CAs. The decision to trust a CA is an important
decision as it ultimately determines the trust afforded a
certificate. The authenticated distribution of trusted CA public
keys (usually in the form of a "self-signed" certificate) is a
security critical out-of-band process that is beyond the scope of
this specification.
In addition, where a key compromise or CA failure occurs for a
trusted CA, the user will need to modify the information provided to
the path validation routine. Selection of too many trusted CAs makes
Housley, et. al. Standards Track [Page 90]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
the trusted CA information difficult to maintain. On the other hand,
selection of only one trusted CA could limit users to a closed
community of users.
The quality of implementations that process certificates also affects
the degree of assurance provided. The path validation algorithm
described in section 6 relies upon the integrity of the trusted CA
information, and especially the integrity of the public keys
associated with the trusted CAs. By substituting public keys for
which an attacker has the private key, an attacker could trick the
user into accepting false certificates.
The binding between a key and certificate subject cannot be stronger
than the cryptographic module implementation and algorithms used to
generate the signature. Short key lengths or weak hash algorithms
will limit the utility of a certificate. CAs are encouraged to note
advances in cryptology so they can employ strong cryptographic
techniques. In addition, CAs SHOULD decline to issue certificates to
CAs or end entities that generate weak signatures.
Inconsistent application of name comparison rules can result in
acceptance of invalid X.509 certification paths, or rejection of
valid ones. The X.500 series of specifications defines rules for
comparing distinguished names that require comparison of strings
without regard to case, character set, multi-character white space
substring, or leading and trailing white space. This specification
relaxes these requirements, requiring support for binary comparison
at a minimum.
CAs MUST encode the distinguished name in the subject field of a CA
certificate identically to the distinguished name in the issuer field
in certificates issued by that CA. If CAs use different encodings,
implementations might fail to recognize name chains for paths that
include this certificate. As a consequence, valid paths could be
rejected.
In addition, name constraints for distinguished names MUST be stated
identically to the encoding used in the subject field or
subjectAltName extension. If not, then name constraints stated as
excludedSubTrees will not match and invalid paths will be accepted
and name constraints expressed as permittedSubtrees will not match
and valid paths will be rejected. To avoid acceptance of invalid
paths, CAs SHOULD state name constraints for distinguished names as
permittedSubtrees wherever possible.
Housley, et. al. Standards Track [Page 91]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
Appendix A. Psuedo-ASN.1 Structures and OIDs
This section describes data objects used by conforming PKI components
in an "ASN.1-like" syntax. This syntax is a hybrid of the 1988 and
1993 ASN.1 syntaxes. The 1988 ASN.1 syntax is augmented with 1993
UNIVERSAL Types UniversalString, BMPString and UTF8String.
The ASN.1 syntax does not permit the inclusion of type statements in
the ASN.1 module, and the 1993 ASN.1 standard does not permit use of
the new UNIVERSAL types in modules using the 1988 syntax. As a
result, this module does not conform to either version of the ASN.1
standard.
This appendix may be converted into 1988 ASN.1 by replacing the
definitions for the UNIVERSAL Types with the 1988 catch-all "ANY".
A.1 Explicitly Tagged Module, 1988 Syntax
PKIX1Explicit88 { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-explicit(18) }
DEFINITIONS EXPLICIT TAGS ::=
BEGIN
-- EXPORTS ALL --
-- IMPORTS NONE --
-- UNIVERSAL Types defined in 1993 and 1998 ASN.1
-- and required by this specification
UniversalString ::= [UNIVERSAL 28] IMPLICIT OCTET STRING
-- UniversalString is defined in ASN.1:1993
BMPString ::= [UNIVERSAL 30] IMPLICIT OCTET STRING
-- BMPString is the subtype of UniversalString and models
-- the Basic Multilingual Plane of ISO/IEC/ITU 10646-1
UTF8String ::= [UNIVERSAL 12] IMPLICIT OCTET STRING
-- The content of this type conforms to RFC 2279.
-- PKIX specific OIDs
id-pkix OBJECT IDENTIFIER ::=
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) }
Housley, et. al. Standards Track [Page 92]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
-- PKIX arcs
id-pe OBJECT IDENTIFIER ::= { id-pkix 1 }
-- arc for private certificate extensions
id-qt OBJECT IDENTIFIER ::= { id-pkix 2 }
-- arc for policy qualifier types
id-kp OBJECT IDENTIFIER ::= { id-pkix 3 }
-- arc for extended key purpose OIDS
id-ad OBJECT IDENTIFIER ::= { id-pkix 48 }
-- arc for access descriptors
-- policyQualifierIds for Internet policy qualifiers
id-qt-cps OBJECT IDENTIFIER ::= { id-qt 1 }
-- OID for CPS qualifier
id-qt-unotice OBJECT IDENTIFIER ::= { id-qt 2 }
-- OID for user notice qualifier
-- access descriptor definitions
id-ad-ocsp OBJECT IDENTIFIER ::= { id-ad 1 }
id-ad-caIssuers OBJECT IDENTIFIER ::= { id-ad 2 }
id-ad-timeStamping OBJECT IDENTIFIER ::= { id-ad 3 }
id-ad-caRepository OBJECT IDENTIFIER ::= { id-ad 5 }
-- attribute data types
Attribute ::= SEQUENCE {
type AttributeType,
values SET OF AttributeValue }
-- at least one value is required
AttributeType ::= OBJECT IDENTIFIER
AttributeValue ::= ANY
AttributeTypeAndValue ::= SEQUENCE {
type AttributeType,
value AttributeValue }
-- suggested naming attributes: Definition of the following
-- information object set may be augmented to meet local
-- requirements. Note that deleting members of the set may
-- prevent interoperability with conforming implementations.
-- presented in pairs: the AttributeType followed by the
-- type definition for the corresponding AttributeValue
--Arc for standard naming attributes
id-at OBJECT IDENTIFIER ::= { joint-iso-ccitt(2) ds(5) 4 }
Housley, et. al. Standards Track [Page 93]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
-- Naming attributes of type X520name
id-at-name AttributeType ::= { id-at 41 }
id-at-surname AttributeType ::= { id-at 4 }
id-at-givenName AttributeType ::= { id-at 42 }
id-at-initials AttributeType ::= { id-at 43 }
id-at-generationQualifier AttributeType ::= { id-at 44 }
X520name ::= CHOICE {
teletexString TeletexString (SIZE (1..ub-name)),
printableString PrintableString (SIZE (1..ub-name)),
universalString UniversalString (SIZE (1..ub-name)),
utf8String UTF8String (SIZE (1..ub-name)),
bmpString BMPString (SIZE (1..ub-name)) }
-- Naming attributes of type X520CommonName
id-at-commonName AttributeType ::= { id-at 3 }
X520CommonName ::= CHOICE {
teletexString TeletexString (SIZE (1..ub-common-name)),
printableString PrintableString (SIZE (1..ub-common-name)),
universalString UniversalString (SIZE (1..ub-common-name)),
utf8String UTF8String (SIZE (1..ub-common-name)),
bmpString BMPString (SIZE (1..ub-common-name)) }
-- Naming attributes of type X520LocalityName
id-at-localityName AttributeType ::= { id-at 7 }
X520LocalityName ::= CHOICE {
teletexString TeletexString (SIZE (1..ub-locality-name)),
printableString PrintableString (SIZE (1..ub-locality-name)),
universalString UniversalString (SIZE (1..ub-locality-name)),
utf8String UTF8String (SIZE (1..ub-locality-name)),
bmpString BMPString (SIZE (1..ub-locality-name)) }
-- Naming attributes of type X520StateOrProvinceName
id-at-stateOrProvinceName AttributeType ::= { id-at 8 }
X520StateOrProvinceName ::= CHOICE {
teletexString TeletexString (SIZE (1..ub-state-name)),
printableString PrintableString (SIZE (1..ub-state-name)),
universalString UniversalString (SIZE (1..ub-state-name)),
utf8String UTF8String (SIZE (1..ub-state-name)),
bmpString BMPString (SIZE(1..ub-state-name)) }
Housley, et. al. Standards Track [Page 94]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
-- Naming attributes of type X520OrganizationName
id-at-organizationName AttributeType ::= { id-at 10 }
X520OrganizationName ::= CHOICE {
teletexString TeletexString
(SIZE (1..ub-organization-name)),
printableString PrintableString
(SIZE (1..ub-organization-name)),
universalString UniversalString
(SIZE (1..ub-organization-name)),
utf8String UTF8String
(SIZE (1..ub-organization-name)),
bmpString BMPString
(SIZE (1..ub-organization-name)) }
-- Naming attributes of type X520OrganizationalUnitName
id-at-organizationalUnitName AttributeType ::= { id-at 11 }
X520OrganizationalUnitName ::= CHOICE {
teletexString TeletexString
(SIZE (1..ub-organizational-unit-name)),
printableString PrintableString
(SIZE (1..ub-organizational-unit-name)),
universalString UniversalString
(SIZE (1..ub-organizational-unit-name)),
utf8String UTF8String
(SIZE (1..ub-organizational-unit-name)),
bmpString BMPString
(SIZE (1..ub-organizational-unit-name)) }
-- Naming attributes of type X520Title
id-at-title AttributeType ::= { id-at 12 }
X520Title ::= CHOICE {
teletexString TeletexString (SIZE (1..ub-title)),
printableString PrintableString (SIZE (1..ub-title)),
universalString UniversalString (SIZE (1..ub-title)),
utf8String UTF8String (SIZE (1..ub-title)),
bmpString BMPString (SIZE (1..ub-title)) }
-- Naming attributes of type X520dnQualifier
id-at-dnQualifier AttributeType ::= { id-at 46 }
X520dnQualifier ::= PrintableString
Housley, et. al. Standards Track [Page 95]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
-- Naming attributes of type X520countryName (digraph from IS 3166)
id-at-countryName AttributeType ::= { id-at 6 }
X520countryName ::= PrintableString (SIZE (2))
-- Naming attributes of type X520SerialNumber
id-at-serialNumber AttributeType ::= { id-at 5 }
X520SerialNumber ::= PrintableString (SIZE (1..ub-serial-number))
-- Naming attributes of type X520Pseudonym
id-at-pseudonym AttributeType ::= { id-at 65 }
X520Pseudonym ::= CHOICE {
teletexString TeletexString (SIZE (1..ub-pseudonym)),
printableString PrintableString (SIZE (1..ub-pseudonym)),
universalString UniversalString (SIZE (1..ub-pseudonym)),
utf8String UTF8String (SIZE (1..ub-pseudonym)),
bmpString BMPString (SIZE (1..ub-pseudonym)) }
-- Naming attributes of type DomainComponent (from RFC 2247)
id-domainComponent AttributeType ::=
{ 0 9 2342 19200300 100 1 25 }
DomainComponent ::= IA5String
-- Legacy attributes
pkcs-9 OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 9 }
id-emailAddress AttributeType ::= { pkcs-9 1 }
EmailAddress ::= IA5String (SIZE (1..ub-emailaddress-length))
-- naming data types --
Name ::= CHOICE { -- only one possibility for now --
rdnSequence RDNSequence }
RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
DistinguishedName ::= RDNSequence
Housley, et. al. Standards Track [Page 96]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
RelativeDistinguishedName ::=
SET SIZE (1 .. MAX) OF AttributeTypeAndValue
-- Directory string type --
DirectoryString ::= CHOICE {
teletexString TeletexString (SIZE (1..MAX)),
printableString PrintableString (SIZE (1..MAX)),
universalString UniversalString (SIZE (1..MAX)),
utf8String UTF8String (SIZE (1..MAX)),
bmpString BMPString (SIZE (1..MAX)) }
-- certificate and CRL specific structures begin here
Certificate ::= SEQUENCE {
tbsCertificate TBSCertificate,
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING }
TBSCertificate ::= SEQUENCE {
version [0] Version DEFAULT v1,
serialNumber CertificateSerialNumber,
signature AlgorithmIdentifier,
issuer Name,
validity Validity,
subject Name,
subjectPublicKeyInfo SubjectPublicKeyInfo,
issuerUniqueID [1] IMPLICIT UniqueIdentifier OPTIONAL,
-- If present, version MUST be v2 or v3
subjectUniqueID [2] IMPLICIT UniqueIdentifier OPTIONAL,
-- If present, version MUST be v2 or v3
extensions [3] Extensions OPTIONAL
-- If present, version MUST be v3 -- }
Version ::= INTEGER { v1(0), v2(1), v3(2) }
CertificateSerialNumber ::= INTEGER
Validity ::= SEQUENCE {
notBefore Time,
notAfter Time }
Time ::= CHOICE {
utcTime UTCTime,
generalTime GeneralizedTime }
UniqueIdentifier ::= BIT STRING
Housley, et. al. Standards Track [Page 97]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
SubjectPublicKeyInfo ::= SEQUENCE {
algorithm AlgorithmIdentifier,
subjectPublicKey BIT STRING }
Extensions ::= SEQUENCE SIZE (1..MAX) OF Extension
Extension ::= SEQUENCE {
extnID OBJECT IDENTIFIER,
critical BOOLEAN DEFAULT FALSE,
extnValue OCTET STRING }
-- CRL structures
CertificateList ::= SEQUENCE {
tbsCertList TBSCertList,
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING }
TBSCertList ::= SEQUENCE {
version Version OPTIONAL,
-- if present, MUST be v2
signature AlgorithmIdentifier,
issuer Name,
thisUpdate Time,
nextUpdate Time OPTIONAL,
revokedCertificates SEQUENCE OF SEQUENCE {
userCertificate CertificateSerialNumber,
revocationDate Time,
crlEntryExtensions Extensions OPTIONAL
-- if present, MUST be v2
} OPTIONAL,
crlExtensions [0] Extensions OPTIONAL }
-- if present, MUST be v2
-- Version, Time, CertificateSerialNumber, and Extensions were
-- defined earlier for use in the certificate structure
AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL }
-- contains a value of the type
-- registered for use with the
-- algorithm object identifier value
-- X.400 address syntax starts here
Housley, et. al. Standards Track [Page 98]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
ORAddress ::= SEQUENCE {
built-in-standard-attributes BuiltInStandardAttributes,
built-in-domain-defined-attributes
BuiltInDomainDefinedAttributes OPTIONAL,
-- see also teletex-domain-defined-attributes
extension-attributes ExtensionAttributes OPTIONAL }
-- Built-in Standard Attributes
BuiltInStandardAttributes ::= SEQUENCE {
country-name CountryName OPTIONAL,
administration-domain-name AdministrationDomainName OPTIONAL,
network-address [0] IMPLICIT NetworkAddress OPTIONAL,
-- see also extended-network-address
terminal-identifier [1] IMPLICIT TerminalIdentifier OPTIONAL,
private-domain-name [2] PrivateDomainName OPTIONAL,
organization-name [3] IMPLICIT OrganizationName OPTIONAL,
-- see also teletex-organization-name
numeric-user-identifier [4] IMPLICIT NumericUserIdentifier
OPTIONAL,
personal-name [5] IMPLICIT PersonalName OPTIONAL,
-- see also teletex-personal-name
organizational-unit-names [6] IMPLICIT OrganizationalUnitNames
OPTIONAL }
-- see also teletex-organizational-unit-names
CountryName ::= [APPLICATION 1] CHOICE {
x121-dcc-code NumericString
(SIZE (ub-country-name-numeric-length)),
iso-3166-alpha2-code PrintableString
(SIZE (ub-country-name-alpha-length)) }
AdministrationDomainName ::= [APPLICATION 2] CHOICE {
numeric NumericString (SIZE (0..ub-domain-name-length)),
printable PrintableString (SIZE (0..ub-domain-name-length)) }
NetworkAddress ::= X121Address -- see also extended-network-address
X121Address ::= NumericString (SIZE (1..ub-x121-address-length))
TerminalIdentifier ::= PrintableString (SIZE
(1..ub-terminal-id-length))
PrivateDomainName ::= CHOICE {
numeric NumericString (SIZE (1..ub-domain-name-length)),
printable PrintableString (SIZE (1..ub-domain-name-length)) }
Housley, et. al. Standards Track [Page 99]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
OrganizationName ::= PrintableString
(SIZE (1..ub-organization-name-length))
-- see also teletex-organization-name
NumericUserIdentifier ::= NumericString
(SIZE (1..ub-numeric-user-id-length))
PersonalName ::= SET {
surname [0] IMPLICIT PrintableString
(SIZE (1..ub-surname-length)),
given-name [1] IMPLICIT PrintableString
(SIZE (1..ub-given-name-length)) OPTIONAL,
initials [2] IMPLICIT PrintableString
(SIZE (1..ub-initials-length)) OPTIONAL,
generation-qualifier [3] IMPLICIT PrintableString
(SIZE (1..ub-generation-qualifier-length))
OPTIONAL }
-- see also teletex-personal-name
OrganizationalUnitNames ::= SEQUENCE SIZE (1..ub-organizational-units)
OF OrganizationalUnitName
-- see also teletex-organizational-unit-names
OrganizationalUnitName ::= PrintableString (SIZE
(1..ub-organizational-unit-name-length))
-- Built-in Domain-defined Attributes
BuiltInDomainDefinedAttributes ::= SEQUENCE SIZE
(1..ub-domain-defined-attributes) OF
BuiltInDomainDefinedAttribute
BuiltInDomainDefinedAttribute ::= SEQUENCE {
type PrintableString (SIZE
(1..ub-domain-defined-attribute-type-length)),
value PrintableString (SIZE
(1..ub-domain-defined-attribute-value-length)) }
-- Extension Attributes
ExtensionAttributes ::= SET SIZE (1..ub-extension-attributes) OF
ExtensionAttribute
ExtensionAttribute ::= SEQUENCE {
extension-attribute-type [0] IMPLICIT INTEGER
(0..ub-extension-attributes),
extension-attribute-value [1]
ANY DEFINED BY extension-attribute-type }
Housley, et. al. Standards Track [Page 100]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
-- Extension types and attribute values
common-name INTEGER ::= 1
CommonName ::= PrintableString (SIZE (1..ub-common-name-length))
teletex-common-name INTEGER ::= 2
TeletexCommonName ::= TeletexString (SIZE (1..ub-common-name-length))
teletex-organization-name INTEGER ::= 3
TeletexOrganizationName ::=
TeletexString (SIZE (1..ub-organization-name-length))
teletex-personal-name INTEGER ::= 4
TeletexPersonalName ::= SET {
surname [0] IMPLICIT TeletexString
(SIZE (1..ub-surname-length)),
given-name [1] IMPLICIT TeletexString
(SIZE (1..ub-given-name-length)) OPTIONAL,
initials [2] IMPLICIT TeletexString
(SIZE (1..ub-initials-length)) OPTIONAL,
generation-qualifier [3] IMPLICIT TeletexString
(SIZE (1..ub-generation-qualifier-length))
OPTIONAL }
teletex-organizational-unit-names INTEGER ::= 5
TeletexOrganizationalUnitNames ::= SEQUENCE SIZE
(1..ub-organizational-units) OF TeletexOrganizationalUnitName
TeletexOrganizationalUnitName ::= TeletexString
(SIZE (1..ub-organizational-unit-name-length))
pds-name INTEGER ::= 7
PDSName ::= PrintableString (SIZE (1..ub-pds-name-length))
physical-delivery-country-name INTEGER ::= 8
PhysicalDeliveryCountryName ::= CHOICE {
x121-dcc-code NumericString (SIZE
(ub-country-name-numeric-length)),
iso-3166-alpha2-code PrintableString
(SIZE (ub-country-name-alpha-length)) }
Housley, et. al. Standards Track [Page 101]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
postal-code INTEGER ::= 9
PostalCode ::= CHOICE {
numeric-code NumericString (SIZE (1..ub-postal-code-length)),
printable-code PrintableString (SIZE (1..ub-postal-code-length)) }
physical-delivery-office-name INTEGER ::= 10
PhysicalDeliveryOfficeName ::= PDSParameter
physical-delivery-office-number INTEGER ::= 11
PhysicalDeliveryOfficeNumber ::= PDSParameter
extension-OR-address-components INTEGER ::= 12
ExtensionORAddressComponents ::= PDSParameter
physical-delivery-personal-name INTEGER ::= 13
PhysicalDeliveryPersonalName ::= PDSParameter
physical-delivery-organization-name INTEGER ::= 14
PhysicalDeliveryOrganizationName ::= PDSParameter
extension-physical-delivery-address-components INTEGER ::= 15
ExtensionPhysicalDeliveryAddressComponents ::= PDSParameter
unformatted-postal-address INTEGER ::= 16
UnformattedPostalAddress ::= SET {
printable-address SEQUENCE SIZE (1..ub-pds-physical-address-lines)
OF PrintableString (SIZE (1..ub-pds-parameter-length))
OPTIONAL,
teletex-string TeletexString
(SIZE (1..ub-unformatted-address-length)) OPTIONAL }
street-address INTEGER ::= 17
StreetAddress ::= PDSParameter
post-office-box-address INTEGER ::= 18
PostOfficeBoxAddress ::= PDSParameter
poste-restante-address INTEGER ::= 19
Housley, et. al. Standards Track [Page 102]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
PosteRestanteAddress ::= PDSParameter
unique-postal-name INTEGER ::= 20
UniquePostalName ::= PDSParameter
local-postal-attributes INTEGER ::= 21
LocalPostalAttributes ::= PDSParameter
PDSParameter ::= SET {
printable-string PrintableString
(SIZE(1..ub-pds-parameter-length)) OPTIONAL,
teletex-string TeletexString
(SIZE(1..ub-pds-parameter-length)) OPTIONAL }
extended-network-address INTEGER ::= 22
ExtendedNetworkAddress ::= CHOICE {
e163-4-address SEQUENCE {
number [0] IMPLICIT NumericString
(SIZE (1..ub-e163-4-number-length)),
sub-address [1] IMPLICIT NumericString
(SIZE (1..ub-e163-4-sub-address-length))
OPTIONAL },
psap-address [0] IMPLICIT PresentationAddress }
PresentationAddress ::= SEQUENCE {
pSelector [0] EXPLICIT OCTET STRING OPTIONAL,
sSelector [1] EXPLICIT OCTET STRING OPTIONAL,
tSelector [2] EXPLICIT OCTET STRING OPTIONAL,
nAddresses [3] EXPLICIT SET SIZE (1..MAX) OF OCTET STRING }
terminal-type INTEGER ::= 23
TerminalType ::= INTEGER {
telex (3),
teletex (4),
g3-facsimile (5),
g4-facsimile (6),
ia5-terminal (7),
videotex (8) } (0..ub-integer-options)
-- Extension Domain-defined Attributes
teletex-domain-defined-attributes INTEGER ::= 6
Housley, et. al. Standards Track [Page 103]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
TeletexDomainDefinedAttributes ::= SEQUENCE SIZE
(1..ub-domain-defined-attributes) OF TeletexDomainDefinedAttribute
TeletexDomainDefinedAttribute ::= SEQUENCE {
type TeletexString
(SIZE (1..ub-domain-defined-attribute-type-length)),
value TeletexString
(SIZE (1..ub-domain-defined-attribute-value-length)) }
-- specifications of Upper Bounds MUST be regarded as mandatory
-- from Annex B of ITU-T X.411 Reference Definition of MTS Parameter
-- Upper Bounds
-- Upper Bounds
ub-name INTEGER ::= 32768
ub-common-name INTEGER ::= 64
ub-locality-name INTEGER ::= 128
ub-state-name INTEGER ::= 128
ub-organization-name INTEGER ::= 64
ub-organizational-unit-name INTEGER ::= 64
ub-title INTEGER ::= 64
ub-serial-number INTEGER ::= 64
ub-match INTEGER ::= 128
ub-emailaddress-length INTEGER ::= 128
ub-common-name-length INTEGER ::= 64
ub-country-name-alpha-length INTEGER ::= 2
ub-country-name-numeric-length INTEGER ::= 3
ub-domain-defined-attributes INTEGER ::= 4
ub-domain-defined-attribute-type-length INTEGER ::= 8
ub-domain-defined-attribute-value-length INTEGER ::= 128
ub-domain-name-length INTEGER ::= 16
ub-extension-attributes INTEGER ::= 256
ub-e163-4-number-length INTEGER ::= 15
ub-e163-4-sub-address-length INTEGER ::= 40
ub-generation-qualifier-length INTEGER ::= 3
ub-given-name-length INTEGER ::= 16
ub-initials-length INTEGER ::= 5
ub-integer-options INTEGER ::= 256
ub-numeric-user-id-length INTEGER ::= 32
ub-organization-name-length INTEGER ::= 64
ub-organizational-unit-name-length INTEGER ::= 32
ub-organizational-units INTEGER ::= 4
ub-pds-name-length INTEGER ::= 16
ub-pds-parameter-length INTEGER ::= 30
ub-pds-physical-address-lines INTEGER ::= 6
ub-postal-code-length INTEGER ::= 16
ub-pseudonym INTEGER ::= 128
ub-surname-length INTEGER ::= 40
Housley, et. al. Standards Track [Page 104]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
ub-terminal-id-length INTEGER ::= 24
ub-unformatted-address-length INTEGER ::= 180
ub-x121-address-length INTEGER ::= 16
-- Note - upper bounds on string types, such as TeletexString, are
-- measured in characters. Excepting PrintableString or IA5String, a
-- significantly greater number of octets will be required to hold
-- such a value. As a minimum, 16 octets, or twice the specified
-- upper bound, whichever is the larger, should be allowed for
-- TeletexString. For UTF8String or UniversalString at least four
-- times the upper bound should be allowed.
END
A.2 Implicitly Tagged Module, 1988 Syntax
PKIX1Implicit88 { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-implicit(19) }
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
-- EXPORTS ALL --
IMPORTS
id-pe, id-kp, id-qt-unotice, id-qt-cps,
-- delete following line if "new" types are supported --
BMPString, UTF8String, -- end "new" types --
ORAddress, Name, RelativeDistinguishedName,
CertificateSerialNumber, Attribute, DirectoryString
FROM PKIX1Explicit88 { iso(1) identified-organization(3)
dod(6) internet(1) security(5) mechanisms(5) pkix(7)
id-mod(0) id-pkix1-explicit(18) };
-- ISO arc for standard certificate and CRL extensions
id-ce OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) 29}
-- authority key identifier OID and syntax
id-ce-authorityKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 35 }
Housley, et. al. Standards Track [Page 105]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
AuthorityKeyIdentifier ::= SEQUENCE {
keyIdentifier [0] KeyIdentifier OPTIONAL,
authorityCertIssuer [1] GeneralNames OPTIONAL,
authorityCertSerialNumber [2] CertificateSerialNumber OPTIONAL }
-- authorityCertIssuer and authorityCertSerialNumber MUST both
-- be present or both be absent
KeyIdentifier ::= OCTET STRING
-- subject key identifier OID and syntax
id-ce-subjectKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 14 }
SubjectKeyIdentifier ::= KeyIdentifier
-- key usage extension OID and syntax
id-ce-keyUsage OBJECT IDENTIFIER ::= { id-ce 15 }
KeyUsage ::= BIT STRING {
digitalSignature (0),
nonRepudiation (1),
keyEncipherment (2),
dataEncipherment (3),
keyAgreement (4),
keyCertSign (5),
cRLSign (6),
encipherOnly (7),
decipherOnly (8) }
-- private key usage period extension OID and syntax
id-ce-privateKeyUsagePeriod OBJECT IDENTIFIER ::= { id-ce 16 }
PrivateKeyUsagePeriod ::= SEQUENCE {
notBefore [0] GeneralizedTime OPTIONAL,
notAfter [1] GeneralizedTime OPTIONAL }
-- either notBefore or notAfter MUST be present
-- certificate policies extension OID and syntax
id-ce-certificatePolicies OBJECT IDENTIFIER ::= { id-ce 32 }
anyPolicy OBJECT IDENTIFIER ::= { id-ce-certificatePolicies 0 }
CertificatePolicies ::= SEQUENCE SIZE (1..MAX) OF PolicyInformation
PolicyInformation ::= SEQUENCE {
Housley, et. al. Standards Track [Page 106]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
policyIdentifier CertPolicyId,
policyQualifiers SEQUENCE SIZE (1..MAX) OF
PolicyQualifierInfo OPTIONAL }
CertPolicyId ::= OBJECT IDENTIFIER
PolicyQualifierInfo ::= SEQUENCE {
policyQualifierId PolicyQualifierId,
qualifier ANY DEFINED BY policyQualifierId }
-- Implementations that recognize additional policy qualifiers MUST
-- augment the following definition for PolicyQualifierId
PolicyQualifierId ::=
OBJECT IDENTIFIER ( id-qt-cps | id-qt-unotice )
-- CPS pointer qualifier
CPSuri ::= IA5String
-- user notice qualifier
UserNotice ::= SEQUENCE {
noticeRef NoticeReference OPTIONAL,
explicitText DisplayText OPTIONAL}
NoticeReference ::= SEQUENCE {
organization DisplayText,
noticeNumbers SEQUENCE OF INTEGER }
DisplayText ::= CHOICE {
ia5String IA5String (SIZE (1..200)),
visibleString VisibleString (SIZE (1..200)),
bmpString BMPString (SIZE (1..200)),
utf8String UTF8String (SIZE (1..200)) }
-- policy mapping extension OID and syntax
id-ce-policyMappings OBJECT IDENTIFIER ::= { id-ce 33 }
PolicyMappings ::= SEQUENCE SIZE (1..MAX) OF SEQUENCE {
issuerDomainPolicy CertPolicyId,
subjectDomainPolicy CertPolicyId }
-- subject alternative name extension OID and syntax
id-ce-subjectAltName OBJECT IDENTIFIER ::= { id-ce 17 }
Housley, et. al. Standards Track [Page 107]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
SubjectAltName ::= GeneralNames
GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
GeneralName ::= CHOICE {
otherName [0] AnotherName,
rfc822Name [1] IA5String,
dNSName [2] IA5String,
x400Address [3] ORAddress,
directoryName [4] Name,
ediPartyName [5] EDIPartyName,
uniformResourceIdentifier [6] IA5String,
iPAddress [7] OCTET STRING,
registeredID [8] OBJECT IDENTIFIER }
-- AnotherName replaces OTHER-NAME ::= TYPE-IDENTIFIER, as
-- TYPE-IDENTIFIER is not supported in the '88 ASN.1 syntax
AnotherName ::= SEQUENCE {
type-id OBJECT IDENTIFIER,
value [0] EXPLICIT ANY DEFINED BY type-id }
EDIPartyName ::= SEQUENCE {
nameAssigner [0] DirectoryString OPTIONAL,
partyName [1] DirectoryString }
-- issuer alternative name extension OID and syntax
id-ce-issuerAltName OBJECT IDENTIFIER ::= { id-ce 18 }
IssuerAltName ::= GeneralNames
id-ce-subjectDirectoryAttributes OBJECT IDENTIFIER ::= { id-ce 9 }
SubjectDirectoryAttributes ::= SEQUENCE SIZE (1..MAX) OF Attribute
-- basic constraints extension OID and syntax
id-ce-basicConstraints OBJECT IDENTIFIER ::= { id-ce 19 }
BasicConstraints ::= SEQUENCE {
cA BOOLEAN DEFAULT FALSE,
pathLenConstraint INTEGER (0..MAX) OPTIONAL }
-- name constraints extension OID and syntax
id-ce-nameConstraints OBJECT IDENTIFIER ::= { id-ce 30 }
Housley, et. al. Standards Track [Page 108]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
NameConstraints ::= SEQUENCE {
permittedSubtrees [0] GeneralSubtrees OPTIONAL,
excludedSubtrees [1] GeneralSubtrees OPTIONAL }
GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
GeneralSubtree ::= SEQUENCE {
base GeneralName,
minimum [0] BaseDistance DEFAULT 0,
maximum [1] BaseDistance OPTIONAL }
BaseDistance ::= INTEGER (0..MAX)
-- policy constraints extension OID and syntax
id-ce-policyConstraints OBJECT IDENTIFIER ::= { id-ce 36 }
PolicyConstraints ::= SEQUENCE {
requireExplicitPolicy [0] SkipCerts OPTIONAL,
inhibitPolicyMapping [1] SkipCerts OPTIONAL }
SkipCerts ::= INTEGER (0..MAX)
-- CRL distribution points extension OID and syntax
id-ce-cRLDistributionPoints OBJECT IDENTIFIER ::= {id-ce 31}
CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
DistributionPoint ::= SEQUENCE {
distributionPoint [0] DistributionPointName OPTIONAL,
reasons [1] ReasonFlags OPTIONAL,
cRLIssuer [2] GeneralNames OPTIONAL }
DistributionPointName ::= CHOICE {
fullName [0] GeneralNames,
nameRelativeToCRLIssuer [1] RelativeDistinguishedName }
ReasonFlags ::= BIT STRING {
unused (0),
keyCompromise (1),
cACompromise (2),
affiliationChanged (3),
superseded (4),
cessationOfOperation (5),
certificateHold (6),
privilegeWithdrawn (7),
aACompromise (8) }
Housley, et. al. Standards Track [Page 109]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
-- extended key usage extension OID and syntax
id-ce-extKeyUsage OBJECT IDENTIFIER ::= {id-ce 37}
ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
KeyPurposeId ::= OBJECT IDENTIFIER
-- permit unspecified key uses
anyExtendedKeyUsage OBJECT IDENTIFIER ::= { id-ce-extKeyUsage 0 }
-- extended key purpose OIDs
id-kp-serverAuth OBJECT IDENTIFIER ::= { id-kp 1 }
id-kp-clientAuth OBJECT IDENTIFIER ::= { id-kp 2 }
id-kp-codeSigning OBJECT IDENTIFIER ::= { id-kp 3 }
id-kp-emailProtection OBJECT IDENTIFIER ::= { id-kp 4 }
id-kp-timeStamping OBJECT IDENTIFIER ::= { id-kp 8 }
id-kp-OCSPSigning OBJECT IDENTIFIER ::= { id-kp 9 }
-- inhibit any policy OID and syntax
id-ce-inhibitAnyPolicy OBJECT IDENTIFIER ::= { id-ce 54 }
InhibitAnyPolicy ::= SkipCerts
-- freshest (delta)CRL extension OID and syntax
id-ce-freshestCRL OBJECT IDENTIFIER ::= { id-ce 46 }
FreshestCRL ::= CRLDistributionPoints
-- authority info access
id-pe-authorityInfoAccess OBJECT IDENTIFIER ::= { id-pe 1 }
AuthorityInfoAccessSyntax ::=
SEQUENCE SIZE (1..MAX) OF AccessDescription
AccessDescription ::= SEQUENCE {
accessMethod OBJECT IDENTIFIER,
accessLocation GeneralName }
-- subject info access
id-pe-subjectInfoAccess OBJECT IDENTIFIER ::= { id-pe 11 }
Housley, et. al. Standards Track [Page 110]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
SubjectInfoAccessSyntax ::=
SEQUENCE SIZE (1..MAX) OF AccessDescription
-- CRL number extension OID and syntax
id-ce-cRLNumber OBJECT IDENTIFIER ::= { id-ce 20 }
CRLNumber ::= INTEGER (0..MAX)
-- issuing distribution point extension OID and syntax
id-ce-issuingDistributionPoint OBJECT IDENTIFIER ::= { id-ce 28 }
IssuingDistributionPoint ::= SEQUENCE {
distributionPoint [0] DistributionPointName OPTIONAL,
onlyContainsUserCerts [1] BOOLEAN DEFAULT FALSE,
onlyContainsCACerts [2] BOOLEAN DEFAULT FALSE,
onlySomeReasons [3] ReasonFlags OPTIONAL,
indirectCRL [4] BOOLEAN DEFAULT FALSE,
onlyContainsAttributeCerts [5] BOOLEAN DEFAULT FALSE }
id-ce-deltaCRLIndicator OBJECT IDENTIFIER ::= { id-ce 27 }
BaseCRLNumber ::= CRLNumber
-- CRL reasons extension OID and syntax
id-ce-cRLReasons OBJECT IDENTIFIER ::= { id-ce 21 }
CRLReason ::= ENUMERATED {
unspecified (0),
keyCompromise (1),
cACompromise (2),
affiliationChanged (3),
superseded (4),
cessationOfOperation (5),
certificateHold (6),
removeFromCRL (8),
privilegeWithdrawn (9),
aACompromise (10) }
-- certificate issuer CRL entry extension OID and syntax
id-ce-certificateIssuer OBJECT IDENTIFIER ::= { id-ce 29 }
CertificateIssuer ::= GeneralNames
-- hold instruction extension OID and syntax
Housley, et. al. Standards Track [Page 111]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
id-ce-holdInstructionCode OBJECT IDENTIFIER ::= { id-ce 23 }
HoldInstructionCode ::= OBJECT IDENTIFIER
-- ANSI x9 holdinstructions
-- ANSI x9 arc holdinstruction arc
holdInstruction OBJECT IDENTIFIER ::=
{joint-iso-itu-t(2) member-body(2) us(840) x9cm(10040) 2}
-- ANSI X9 holdinstructions referenced by this standard
id-holdinstruction-none OBJECT IDENTIFIER ::=
{holdInstruction 1} -- deprecated
id-holdinstruction-callissuer OBJECT IDENTIFIER ::=
{holdInstruction 2}
id-holdinstruction-reject OBJECT IDENTIFIER ::=
{holdInstruction 3}
-- invalidity date CRL entry extension OID and syntax
id-ce-invalidityDate OBJECT IDENTIFIER ::= { id-ce 24 }
InvalidityDate ::= GeneralizedTime
END
Appendix B. ASN.1 Notes
CAs MUST force the serialNumber to be a non-negative integer, that
is, the sign bit in the DER encoding of the INTEGER value MUST be
zero - this can be done by adding a leading (leftmost) `00'H octet if
necessary. This removes a potential ambiguity in mapping between a
string of octets and an integer value.
As noted in section 4.1.2.2, serial numbers can be expected to
contain long integers. Certificate users MUST be able to handle
serialNumber values up to 20 octets in length. Conformant CAs MUST
NOT use serialNumber values longer than 20 octets.
As noted in section 5.2.3, CRL numbers can be expected to contain
long integers. CRL validators MUST be able to handle cRLNumber
values up to 20 octets in length. Conformant CRL issuers MUST NOT
use cRLNumber values longer than 20 octets.
Housley, et. al. Standards Track [Page 112]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
The construct "SEQUENCE SIZE (1..MAX) OF" appears in several ASN.1
constructs. A valid ASN.1 sequence will have zero or more entries.
The SIZE (1..MAX) construct constrains the sequence to have at least
one entry. MAX indicates the upper bound is unspecified.
Implementations are free to choose an upper bound that suits their
environment.
The construct "positiveInt ::= INTEGER (0..MAX)" defines positiveInt
as a subtype of INTEGER containing integers greater than or equal to
zero. The upper bound is unspecified. Implementations are free to
select an upper bound that suits their environment.
The character string type PrintableString supports a very basic Latin
character set: the lower case letters 'a' through 'z', upper case
letters 'A' through 'Z', the digits '0' through '9', eleven special
characters ' = ( ) + , - . / : ? and space.
Implementers should note that the at sign ('@') and underscore ('_')
characters are not supported by the ASN.1 type PrintableString.
These characters often appear in internet addresses. Such addresses
MUST be encoded using an ASN.1 type that supports them. They are
usually encoded as IA5String in either the emailAddress attribute
within a distinguished name or the rfc822Name field of GeneralName.
Conforming implementations MUST NOT encode strings which include
either the at sign or underscore character as PrintableString.
The character string type TeletexString is a superset of
PrintableString. TeletexString supports a fairly standard (ASCII-
like) Latin character set, Latin characters with non-spacing accents
and Japanese characters.
Named bit lists are BIT STRINGs where the values have been assigned
names. This specification makes use of named bit lists in the
definitions for the key usage, CRL distribution points and freshest
CRL certificate extensions, as well as the freshest CRL and issuing
distribution point CRL extensions. When DER encoding a named bit
list, trailing zeroes MUST be omitted. That is, the encoded value
ends with the last named bit that is set to one.
The character string type UniversalString supports any of the
characters allowed by ISO 10646-1 [ISO 10646]. ISO 10646-1 is the
Universal multiple-octet coded Character Set (UCS). ISO 10646-1
specifies the architecture and the "basic multilingual plane" -- a
large standard character set which includes all major world character
standards.
Housley, et. al. Standards Track [Page 113]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
The character string type UTF8String was introduced in the 1997
version of ASN.1, and UTF8String was added to the list of choices for
DirectoryString in the 2001 version of X.520 [X.520]. UTF8String is
a universal type and has been assigned tag number 12. The content of
UTF8String was defined by RFC 2044 [RFC 2044] and updated in RFC 2279
[RFC 2279].
In anticipation of these changes, and in conformance with IETF Best
Practices codified in RFC 2277 [RFC 2277], IETF Policy on Character
Sets and Languages, this document includes UTF8String as a choice in
DirectoryString and the CPS qualifier extensions.
Implementers should note that the DER encoding of the SET OF values
requires ordering of the encodings of the values. In particular,
this issue arises with respect to distinguished names.
Implementers should note that the DER encoding of SET or SEQUENCE
components whose value is the DEFAULT omit the component from the
encoded certificate or CRL. For example, a BasicConstraints
extension whose cA value is FALSE would omit the cA boolean from the
encoded certificate.
Object Identifiers (OIDs) are used throughout this specification to
identify certificate policies, public key and signature algorithms,
certificate extensions, etc. There is no maximum size for OIDs.
This specification mandates support for OIDs which have arc elements
with values that are less than 2^28, that is, they MUST be between 0
and 268,435,455, inclusive. This allows each arc element to be
represented within a single 32 bit word. Implementations MUST also
support OIDs where the length of the dotted decimal (see [RFC 2252],
section 4.1) string representation can be up to 100 bytes
(inclusive). Implementations MUST be able to handle OIDs with up to
20 elements (inclusive). CAs SHOULD NOT issue certificates which
contain OIDs that exceed these requirements. Likewise, CRL issuers
SHOULD NOT issue CRLs which contain OIDs that exceed these
requirements.
Implementors are warned that the X.500 standards community has
developed a series of extensibility rules. These rules determine
when an ASN.1 definition can be changed without assigning a new
object identifier (OID). For example, at least two extension
definitions included in RFC 2459 [RFC 2459], the predecessor to this
profile document, have different ASN.1 definitions in this
specification, but the same OID is used. If unknown elements appear
within an extension, and the extension is not marked critical, those
unknown elements ought to be ignored, as follows:
(a) ignore all unknown bit name assignments within a bit string;
Housley, et. al. Standards Track [Page 114]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(b) ignore all unknown named numbers in an ENUMERATED type or
INTEGER type that is being used in the enumerated style, provided
the number occurs as an optional element of a SET or SEQUENCE; and
(c) ignore all unknown elements in SETs, at the end of SEQUENCEs,
or in CHOICEs where the CHOICE is itself an optional element of a
SET or SEQUENCE.
If an extension containing unexpected values is marked critical, the
implementation MUST reject the certificate or CRL containing the
unrecognized extension.
Appendix C. Examples
This section contains four examples: three certificates and a CRL.
The first two certificates and the CRL comprise a minimal
certification path.
Section C.1 contains an annotated hex dump of a "self-signed"
certificate issued by a CA whose distinguished name is
cn=us,o=gov,ou=nist. The certificate contains a DSA public key with
parameters, and is signed by the corresponding DSA private key.
Section C.2 contains an annotated hex dump of an end entity
certificate. The end entity certificate contains a DSA public key,
and is signed by the private key corresponding to the "self-signed"
certificate in section C.1.
Section C.3 contains a dump of an end entity certificate which
contains an RSA public key and is signed with RSA and MD5. This
certificate is not part of the minimal certification path.
Section C.4 contains an annotated hex dump of a CRL. The CRL is
issued by the CA whose distinguished name is cn=us,o=gov,ou=nist and
the list of revoked certificates includes the end entity certificate
presented in C.2.
The certificates were processed using Peter Gutman's dumpasn1 utility
to generate the output. The source for the dumpasn1 utility is
available at <http://www.cs.auckland.ac.nz/~pgut001/dumpasn1.c>. The
binaries for the certificates and CRLs are available at
<http://csrc.nist.gov/pki/pkixtools>.
C.1 Certificate
This section contains an annotated hex dump of a 699 byte version 3
certificate. The certificate contains the following information:
(a) the serial number is 23 (17 hex);
Housley, et. al. Standards Track [Page 115]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(b) the certificate is signed with DSA and the SHA-1 hash algorithm;
(c) the issuer's distinguished name is OU=NIST; O=gov; C=US
(d) and the subject's distinguished name is OU=NIST; O=gov; C=US
(e) the certificate was issued on June 30, 1997 and will expire on
December 31, 1997;
(f) the certificate contains a 1024 bit DSA public key with
parameters;
(g) the certificate contains a subject key identifier extension
generated using method (1) of section 4.2.1.2; and
(h) the certificate is a CA certificate (as indicated through the
basic constraints extension.)
0 30 699: SEQUENCE {
4 30 635: SEQUENCE {
8 A0 3: [0] {
10 02 1: INTEGER 2
: }
13 02 1: INTEGER 17
16 30 9: SEQUENCE {
18 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
: }
27 30 42: SEQUENCE {
29 31 11: SET {
31 30 9: SEQUENCE {
33 06 3: OBJECT IDENTIFIER countryName (2 5 4 6)
38 13 2: PrintableString 'US'
: }
: }
42 31 12: SET {
44 30 10: SEQUENCE {
46 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10)
51 13 3: PrintableString 'gov'
: }
: }
56 31 13: SET {
58 30 11: SEQUENCE {
60 06 3: OBJECT IDENTIFIER
: organizationalUnitName (2 5 4 11)
65 13 4: PrintableString 'NIST'
: }
: }
: }
71 30 30: SEQUENCE {
73 17 13: UTCTime '970630000000Z'
88 17 13: UTCTime '971231000000Z'
: }
103 30 42: SEQUENCE {
105 31 11: SET {
Housley, et. al. Standards Track [Page 116]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
107 30 9: SEQUENCE {
109 06 3: OBJECT IDENTIFIER countryName (2 5 4 6)
114 13 2: PrintableString 'US'
: }
: }
118 31 12: SET {
120 30 10: SEQUENCE {
122 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10)
127 13 3: PrintableString 'gov'
: }
: }
132 31 13: SET {
134 30 11: SEQUENCE {
136 06 3: OBJECT IDENTIFIER
: organizationalUnitName (2 5 4 11)
141 13 4: PrintableString 'NIST'
: }
: }
: }
147 30 440: SEQUENCE {
151 30 300: SEQUENCE {
155 06 7: OBJECT IDENTIFIER dsa (1 2 840 10040 4 1)
164 30 287: SEQUENCE {
168 02 129: INTEGER
: 00 B6 8B 0F 94 2B 9A CE A5 25 C6 F2 ED FC
: FB 95 32 AC 01 12 33 B9 E0 1C AD 90 9B BC
: 48 54 9E F3 94 77 3C 2C 71 35 55 E6 FE 4F
: 22 CB D5 D8 3E 89 93 33 4D FC BD 4F 41 64
: 3E A2 98 70 EC 31 B4 50 DE EB F1 98 28 0A
: C9 3E 44 B3 FD 22 97 96 83 D0 18 A3 E3 BD
: 35 5B FF EE A3 21 72 6A 7B 96 DA B9 3F 1E
: 5A 90 AF 24 D6 20 F0 0D 21 A7 D4 02 B9 1A
: FC AC 21 FB 9E 94 9E 4B 42 45 9E 6A B2 48
: 63 FE 43
300 02 21: INTEGER
: 00 B2 0D B0 B1 01 DF 0C 66 24 FC 13 92 BA
: 55 F7 7D 57 74 81 E5
323 02 129: INTEGER
: 00 9A BF 46 B1 F5 3F 44 3D C9 A5 65 FB 91
: C0 8E 47 F1 0A C3 01 47 C2 44 42 36 A9 92
: 81 DE 57 C5 E0 68 86 58 00 7B 1F F9 9B 77
: A1 C5 10 A5 80 91 78 51 51 3C F6 FC FC CC
: 46 C6 81 78 92 84 3D F4 93 3D 0C 38 7E 1A
: 5B 99 4E AB 14 64 F6 0C 21 22 4E 28 08 9C
: 92 B9 66 9F 40 E8 95 F6 D5 31 2A EF 39 A2
: 62 C7 B2 6D 9E 58 C4 3A A8 11 81 84 6D AF
: F8 B4 19 B4 C2 11 AE D0 22 3B AA 20 7F EE
: 1E 57 18
Housley, et. al. Standards Track [Page 117]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
: }
: }
455 03 133: BIT STRING 0 unused bits, encapsulates {
459 02 129: INTEGER
: 00 B5 9E 1F 49 04 47 D1 DB F5 3A DD CA 04
: 75 E8 DD 75 F6 9B 8A B1 97 D6 59 69 82 D3
: 03 4D FD 3B 36 5F 4A F2 D1 4E C1 07 F5 D1
: 2A D3 78 77 63 56 EA 96 61 4D 42 0B 7A 1D
: FB AB 91 A4 CE DE EF 77 C8 E5 EF 20 AE A6
: 28 48 AF BE 69 C3 6A A5 30 F2 C2 B9 D9 82
: 2B 7D D9 C4 84 1F DE 0D E8 54 D7 1B 99 2E
: B3 D0 88 F6 D6 63 9B A7 E2 0E 82 D4 3B 8A
: 68 1B 06 56 31 59 0B 49 EB 99 A5 D5 81 41
: 7B C9 55
: }
: }
591 A3 50: [3] {
593 30 48: SEQUENCE {
595 30 29: SEQUENCE {
597 06 3: OBJECT IDENTIFIER
: subjectKeyIdentifier (2 5 29 14)
602 04 22: OCTET STRING, encapsulates {
604 04 20: OCTET STRING
: 86 CA A5 22 81 62 EF AD 0A 89 BC AD 72 41
: 2C 29 49 F4 86 56
: }
: }
626 30 15: SEQUENCE {
628 06 3: OBJECT IDENTIFIER basicConstraints (2 5 29 19)
633 01 1: BOOLEAN TRUE
636 04 5: OCTET STRING, encapsulates {
638 30 3: SEQUENCE {
640 01 1: BOOLEAN TRUE
: }
: }
: }
: }
: }
: }
643 30 9: SEQUENCE {
645 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
: }
654 03 47: BIT STRING 0 unused bits, encapsulates {
657 30 44: SEQUENCE {
659 02 20: INTEGER
: 43 1B CF 29 25 45 C0 4E 52 E7 7D D6 FC B1
: 66 4C 83 CF 2D 77
681 02 20: INTEGER
Housley, et. al. Standards Track [Page 118]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
: 0B 5B 9A 24 11 98 E8 F3 86 90 04 F6 08 A9
: E1 8D A5 CC 3A D4
: }
: }
: }
C.2 Certificate
This section contains an annotated hex dump of a 730 byte version 3
certificate. The certificate contains the following information:
(a) the serial number is 18 (12 hex);
(b) the certificate is signed with DSA and the SHA-1 hash algorithm;
(c) the issuer's distinguished name is OU=nist; O=gov; C=US
(d) and the subject's distinguished name is CN=Tim Polk; OU=nist;
O=gov; C=US
(e) the certificate was valid from July 30, 1997 through December 1,
1997;
(f) the certificate contains a 1024 bit DSA public key;
(g) the certificate is an end entity certificate, as the basic
constraints extension is not present;
(h) the certificate contains an authority key identifier extension
matching the subject key identifier of the certificate in Appendix
C.1; and
(i) the certificate includes one alternative name - an RFC 822
address of "wpolk@nist.gov".
0 30 730: SEQUENCE {
4 30 665: SEQUENCE {
8 A0 3: [0] {
10 02 1: INTEGER 2
: }
13 02 1: INTEGER 18
16 30 9: SEQUENCE {
18 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
: }
27 30 42: SEQUENCE {
29 31 11: SET {
31 30 9: SEQUENCE {
33 06 3: OBJECT IDENTIFIER countryName (2 5 4 6)
38 13 2: PrintableString 'US'
: }
: }
42 31 12: SET {
44 30 10: SEQUENCE {
46 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10)
51 13 3: PrintableString 'gov'
: }
: }
Housley, et. al. Standards Track [Page 119]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
56 31 13: SET {
58 30 11: SEQUENCE {
60 06 3: OBJECT IDENTIFIER
: organizationalUnitName (2 5 4 11)
65 13 4: PrintableString 'NIST'
: }
: }
: }
71 30 30: SEQUENCE {
73 17 13: UTCTime '970730000000Z'
88 17 13: UTCTime '971201000000Z'
: }
103 30 61: SEQUENCE {
105 31 11: SET {
107 30 9: SEQUENCE {
109 06 3: OBJECT IDENTIFIER countryName (2 5 4 6)
114 13 2: PrintableString 'US'
: }
: }
118 31 12: SET {
120 30 10: SEQUENCE {
122 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10)
127 13 3: PrintableString 'gov'
: }
: }
132 31 13: SET {
134 30 11: SEQUENCE {
136 06 3: OBJECT IDENTIFIER
: organizationalUnitName (2 5 4 11)
141 13 4: PrintableString 'NIST'
: }
: }
147 31 17: SET {
149 30 15: SEQUENCE {
151 06 3: OBJECT IDENTIFIER commonName (2 5 4 3)
156 13 8: PrintableString 'Tim Polk'
: }
: }
: }
166 30 439: SEQUENCE {
170 30 300: SEQUENCE {
174 06 7: OBJECT IDENTIFIER dsa (1 2 840 10040 4 1)
183 30 287: SEQUENCE {
187 02 129: INTEGER
: 00 B6 8B 0F 94 2B 9A CE A5 25 C6 F2 ED FC
: FB 95 32 AC 01 12 33 B9 E0 1C AD 90 9B BC
: 48 54 9E F3 94 77 3C 2C 71 35 55 E6 FE 4F
: 22 CB D5 D8 3E 89 93 33 4D FC BD 4F 41 64
Housley, et. al. Standards Track [Page 120]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
: 3E A2 98 70 EC 31 B4 50 DE EB F1 98 28 0A
: C9 3E 44 B3 FD 22 97 96 83 D0 18 A3 E3 BD
: 35 5B FF EE A3 21 72 6A 7B 96 DA B9 3F 1E
: 5A 90 AF 24 D6 20 F0 0D 21 A7 D4 02 B9 1A
: FC AC 21 FB 9E 94 9E 4B 42 45 9E 6A B2 48
: 63 FE 43
319 02 21: INTEGER
: 00 B2 0D B0 B1 01 DF 0C 66 24 FC 13 92 BA
: 55 F7 7D 57 74 81 E5
342 02 129: INTEGER
: 00 9A BF 46 B1 F5 3F 44 3D C9 A5 65 FB 91
: C0 8E 47 F1 0A C3 01 47 C2 44 42 36 A9 92
: 81 DE 57 C5 E0 68 86 58 00 7B 1F F9 9B 77
: A1 C5 10 A5 80 91 78 51 51 3C F6 FC FC CC
: 46 C6 81 78 92 84 3D F4 93 3D 0C 38 7E 1A
: 5B 99 4E AB 14 64 F6 0C 21 22 4E 28 08 9C
: 92 B9 66 9F 40 E8 95 F6 D5 31 2A EF 39 A2
: 62 C7 B2 6D 9E 58 C4 3A A8 11 81 84 6D AF
: F8 B4 19 B4 C2 11 AE D0 22 3B AA 20 7F EE
: 1E 57 18
: }
: }
474 03 132: BIT STRING 0 unused bits, encapsulates {
478 02 128: INTEGER
: 30 B6 75 F7 7C 20 31 AE 38 BB 7E 0D 2B AB
: A0 9C 4B DF 20 D5 24 13 3C CD 98 E5 5F 6C
: B7 C1 BA 4A BA A9 95 80 53 F0 0D 72 DC 33
: 37 F4 01 0B F5 04 1F 9D 2E 1F 62 D8 84 3A
: 9B 25 09 5A 2D C8 46 8E 2B D4 F5 0D 3B C7
: 2D C6 6C B9 98 C1 25 3A 44 4E 8E CA 95 61
: 35 7C CE 15 31 5C 23 13 1E A2 05 D1 7A 24
: 1C CB D3 72 09 90 FF 9B 9D 28 C0 A1 0A EC
: 46 9F 0D B8 D0 DC D0 18 A6 2B 5E F9 8F B5
: 95 BE
: }
: }
609 A3 62: [3] {
611 30 60: SEQUENCE {
613 30 25: SEQUENCE {
615 06 3: OBJECT IDENTIFIER subjectAltName (2 5 29 17)
620 04 18: OCTET STRING, encapsulates {
622 30 16: SEQUENCE {
624 81 14: [1] 'wpolk@nist.gov'
: }
: }
: }
640 30 31: SEQUENCE {
642 06 3: OBJECT IDENTIFIER
Housley, et. al. Standards Track [Page 121]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
: authorityKeyIdentifier (2 5 29 35)
647 04 24: OCTET STRING, encapsulates {
649 30 22: SEQUENCE {
651 80 20: [0]
: 86 CA A5 22 81 62 EF AD 0A 89 BC AD 72
: 41 2C 29 49 F4 86 56
: }
: }
: }
: }
: }
: }
673 30 9: SEQUENCE {
675 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
: }
684 03 48: BIT STRING 0 unused bits, encapsulates {
687 30 45: SEQUENCE {
689 02 20: INTEGER
: 36 97 CB E3 B4 2C E1 BB 61 A9 D3 CC 24 CC
: 22 92 9F F4 F5 87
711 02 21: INTEGER
: 00 AB C9 79 AF D2 16 1C A9 E3 68 A9 14 10
: B4 A0 2E FF 22 5A 73
: }
: }
: }
C.3 End Entity Certificate Using RSA
This section contains an annotated hex dump of a 654 byte version 3
certificate. The certificate contains the following information:
(a) the serial number is 256;
(b) the certificate is signed with RSA and the SHA-1 hash algorithm;
(c) the issuer's distinguished name is OU=NIST; O=gov; C=US
(d) and the subject's distinguished name is CN=Tim Polk; OU=NIST;
O=gov; C=US
(e) the certificate was issued on May 21, 1996 at 09:58:26 and
expired on May 21, 1997 at 09:58:26;
(f) the certificate contains a 1024 bit RSA public key;
(g) the certificate is an end entity certificate (not a CA
certificate);
(h) the certificate includes an alternative subject name of
"<http://www.itl.nist.gov/div893/staff/polk/index.html>" and an
alternative issuer name of "<http://www.nist.gov/>" - both are URLs;
(i) the certificate include an authority key identifier extension
and a certificate policies extension specifying the policy OID
2.16.840.1.101.3.2.1.48.9; and
Housley, et. al. Standards Track [Page 122]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
(j) the certificate includes a critical key usage extension
specifying that the public key is intended for verification of
digital signatures.
0 30 654: SEQUENCE {
4 30 503: SEQUENCE {
8 A0 3: [0] {
10 02 1: INTEGER 2
: }
13 02 2: INTEGER 256
17 30 13: SEQUENCE {
19 06 9: OBJECT IDENTIFIER
: sha1withRSAEncryption (1 2 840 113549 1 1 5)
30 05 0: NULL
: }
32 30 42: SEQUENCE {
34 31 11: SET {
36 30 9: SEQUENCE {
38 06 3: OBJECT IDENTIFIER countryName (2 5 4 6)
43 13 2: PrintableString 'US'
: }
: }
47 31 12: SET {
49 30 10: SEQUENCE {
51 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10)
56 13 3: PrintableString 'gov'
: }
: }
61 31 13: SET {
63 30 11: SEQUENCE {
65 06 3: OBJECT IDENTIFIER
: organizationalUnitName (2 5 4 11)
70 13 4: PrintableString 'NIST'
: }
: }
: }
76 30 30: SEQUENCE {
78 17 13: UTCTime '960521095826Z'
93 17 13: UTCTime '970521095826Z'
: }
108 30 61: SEQUENCE {
110 31 11: SET {
112 30 9: SEQUENCE {
114 06 3: OBJECT IDENTIFIER countryName (2 5 4 6)
119 13 2: PrintableString 'US'
: }
: }
123 31 12: SET {
Housley, et. al. Standards Track [Page 123]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
125 30 10: SEQUENCE {
127 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10)
132 13 3: PrintableString 'gov'
: }
: }
137 31 13: SET {
139 30 11: SEQUENCE {
141 06 3: OBJECT IDENTIFIER
: organizationalUnitName (2 5 4 11)
146 13 4: PrintableString 'NIST'
: }
: }
152 31 17: SET {
154 30 15: SEQUENCE {
156 06 3: OBJECT IDENTIFIER commonName (2 5 4 3)
161 13 8: PrintableString 'Tim Polk'
: }
: }
: }
171 30 159: SEQUENCE {
174 30 13: SEQUENCE {
176 06 9: OBJECT IDENTIFIER
: rsaEncryption (1 2 840 113549 1 1 1)
187 05 0: NULL
: }
189 03 141: BIT STRING 0 unused bits, encapsulates {
193 30 137: SEQUENCE {
196 02 129: INTEGER
: 00 E1 6A E4 03 30 97 02 3C F4 10 F3 B5 1E
: 4D 7F 14 7B F6 F5 D0 78 E9 A4 8A F0 A3 75
: EC ED B6 56 96 7F 88 99 85 9A F2 3E 68 77
: 87 EB 9E D1 9F C0 B4 17 DC AB 89 23 A4 1D
: 7E 16 23 4C 4F A8 4D F5 31 B8 7C AA E3 1A
: 49 09 F4 4B 26 DB 27 67 30 82 12 01 4A E9
: 1A B6 C1 0C 53 8B 6C FC 2F 7A 43 EC 33 36
: 7E 32 B2 7B D5 AA CF 01 14 C6 12 EC 13 F2
: 2D 14 7A 8B 21 58 14 13 4C 46 A3 9A F2 16
: 95 FF 23
328 02 3: INTEGER 65537
: }
: }
: }
333 A3 175: [3] {
336 30 172: SEQUENCE {
339 30 63: SEQUENCE {
341 06 3: OBJECT IDENTIFIER subjectAltName (2 5 29 17)
346 04 56: OCTET STRING, encapsulates {
348 30 54: SEQUENCE {
Housley, et. al. Standards Track [Page 124]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
350 86 52: [6]
: 'http://www.itl.nist.gov/div893/staff/'
: 'polk/index.html'
: }
: }
: }
404 30 31: SEQUENCE {
406 06 3: OBJECT IDENTIFIER issuerAltName (2 5 29 18)
411 04 24: OCTET STRING, encapsulates {
413 30 22: SEQUENCE {
415 86 20: [6] 'http://www.nist.gov/'
: }
: }
: }
437 30 31: SEQUENCE {
439 06 3: OBJECT IDENTIFIER
: authorityKeyIdentifier (2 5 29 35)
444 04 24: OCTET STRING, encapsulates {
446 30 22: SEQUENCE {
448 80 20: [0]
: 08 68 AF 85 33 C8 39 4A 7A F8 82 93 8E
: 70 6A 4A 20 84 2C 32
: }
: }
: }
470 30 23: SEQUENCE {
472 06 3: OBJECT IDENTIFIER
: certificatePolicies (2 5 29 32)
477 04 16: OCTET STRING, encapsulates {
479 30 14: SEQUENCE {
481 30 12: SEQUENCE {
483 06 10: OBJECT IDENTIFIER
: '2 16 840 1 101 3 2 1 48 9'
: }
: }
: }
: }
495 30 14: SEQUENCE {
497 06 3: OBJECT IDENTIFIER keyUsage (2 5 29 15)
502 01 1: BOOLEAN TRUE
505 04 4: OCTET STRING, encapsulates {
507 03 2: BIT STRING 7 unused bits
: '1'B (bit 0)
: }
: }
: }
: }
: }
Housley, et. al. Standards Track [Page 125]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
511 30 13: SEQUENCE {
513 06 9: OBJECT IDENTIFIER
: sha1withRSAEncryption (1 2 840 113549 1 1 5)
524 05 0: NULL
: }
526 03 129: BIT STRING 0 unused bits
: 1E 07 77 6E 66 B5 B6 B8 57 F0 03 DC 6F 77
: 6D AF 55 1D 74 E5 CE 36 81 FC 4B C5 F4 47
: 82 C4 0A 25 AA 8D D6 7D 3A 89 AB 44 34 39
: F6 BD 61 1A 78 85 7A B8 1E 92 A2 22 2F CE
: 07 1A 08 8E F1 46 03 59 36 4A CB 60 E6 03
: 40 01 5B 2A 44 D6 E4 7F EB 43 5E 74 0A E6
: E4 F9 3E E1 44 BE 1F E7 5F 5B 2C 41 8D 08
: BD 26 FE 6A A6 C3 2F B2 3B 41 12 6B C1 06
: 8A B8 4C 91 59 EB 2F 38 20 2A 67 74 20 0B
: 77 F3
: }
C.4 Certificate Revocation List
This section contains an annotated hex dump of a version 2 CRL with
one extension (cRLNumber). The CRL was issued by OU=NIST; O=gov;
C=US on August 7, 1997; the next scheduled issuance was September 7,
1997. The CRL includes one revoked certificates: serial number 18
(12 hex), which was revoked on July 31, 1997 due to keyCompromise.
The CRL itself is number 18, and it was signed with DSA and SHA-1.
0 30 203: SEQUENCE {
3 30 140: SEQUENCE {
6 02 1: INTEGER 1
9 30 9: SEQUENCE {
11 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
: }
20 30 42: SEQUENCE {
22 31 11: SET {
24 30 9: SEQUENCE {
26 06 3: OBJECT IDENTIFIER countryName (2 5 4 6)
31 13 2: PrintableString 'US'
: }
: }
35 31 12: SET {
37 30 10: SEQUENCE {
39 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10)
44 13 3: PrintableString 'gov'
: }
: }
49 31 13: SET {
51 30 11: SEQUENCE {
Housley, et. al. Standards Track [Page 126]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
53 06 3: OBJECT IDENTIFIER
: organizationalUnitName (2 5 4 11)
58 13 4: PrintableString 'NIST'
: }
: }
: }
64 17 13: UTCTime '970807000000Z'
79 17 13: UTCTime '970907000000Z'
94 30 34: SEQUENCE {
96 30 32: SEQUENCE {
98 02 1: INTEGER 18
101 17 13: UTCTime '970731000000Z'
116 30 12: SEQUENCE {
118 30 10: SEQUENCE {
120 06 3: OBJECT IDENTIFIER cRLReason (2 5 29 21)
125 04 3: OCTET STRING, encapsulates {
127 0A 1: ENUMERATED 1
: }
: }
: }
: }
: }
130 A0 14: [0] {
132 30 12: SEQUENCE {
134 30 10: SEQUENCE {
136 06 3: OBJECT IDENTIFIER cRLNumber (2 5 29 20)
141 04 3: OCTET STRING, encapsulates {
143 02 1: INTEGER 12
: }
: }
: }
: }
: }
146 30 9: SEQUENCE {
148 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
: }
157 03 47: BIT STRING 0 unused bits, encapsulates {
160 30 44: SEQUENCE {
162 02 20: INTEGER
: 22 4E 9F 43 BA 95 06 34 F2 BB 5E 65 DB A6
: 80 05 C0 3A 29 47
184 02 20: INTEGER
: 59 1A 57 C9 82 D7 02 21 14 C3 D4 0B 32 1B
: 96 16 B1 1F 46 5A
: }
: }
: }
Housley, et. al. Standards Track [Page 127]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
Author Addresses
Russell Housley
RSA Laboratories
918 Spring Knoll Drive
Herndon, VA 20170
USA
EMail: rhousley@rsasecurity.com
Warwick Ford
VeriSign, Inc.
401 Edgewater Place
Wakefield, MA 01880
USA
EMail: wford@verisign.com
Tim Polk
NIST
Building 820, Room 426
Gaithersburg, MD 20899
USA
EMail: wpolk@nist.gov
David Solo
Citigroup
909 Third Ave, 16th Floor
New York, NY 10043
USA
EMail: dsolo@alum.mit.edu
Housley, et. al. Standards Track [Page 128]
RFC 3280 Internet X.509 Public Key Infrastructure April 2002
Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Housley, et. al. Standards Track [Page 129]
|