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
|
/*
* Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* @test
* @bug 8225603
* @summary Tests whether modInverse() completes in a reasonable time
* @run main/othervm ModInvTime
*/
import java.math.BigInteger;
public class ModInvTime {
public static void main(String[] args) throws InterruptedException {
BigInteger prime = new BigInteger("39402006196394479212279040100143613805079739270465446667946905279627659399113263569398956308152294913554433653942643");
BigInteger s = new BigInteger("9552729729729327851382626410162104591956625415831952158766936536163093322096473638446154604799898109762512409920799");
System.out.format("int length: %d, modulus length: %d%n",
s.bitLength(), prime.bitLength());
System.out.println("Computing modular inverse ...");
BigInteger mi = s.modInverse(prime);
System.out.format("Modular inverse: %s%n", mi);
check(s, prime, mi);
BigInteger ns = s.negate();
BigInteger nmi = ns.modInverse(prime);
System.out.format("Modular inverse of negation: %s%n", nmi);
check(ns, prime, nmi);
}
public static void check(BigInteger val, BigInteger mod, BigInteger inv) {
BigInteger r = inv.multiply(val).remainder(mod);
if (r.signum() == -1)
r = r.add(mod);
if (!r.equals(BigInteger.ONE))
throw new RuntimeException("Numerically incorrect modular inverse");
}
}
|
