File: rsa-keygen.c

package info (click to toggle)
nettle 2.7.1-1~bpo70%2B1
  • links: PTS, VCS
  • area: main
  • in suites: wheezy-backports
  • size: 5,648 kB
  • sloc: ansic: 40,319; asm: 9,808; sh: 3,517; makefile: 768; cpp: 71; awk: 7
file content (204 lines) | stat: -rw-r--r-- 4,756 bytes parent folder | download | duplicates (3)
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
/* rsa-keygen.c
 *
 * Generation of RSA keypairs
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2002 Niels Möller
 *  
 * The nettle library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 * 
 * The nettle library 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 Lesser General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with the nettle library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02111-1301, USA.
 */

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include <assert.h>
#include <stdlib.h>

#include "rsa.h"
#include "bignum.h"

#ifndef DEBUG
# define DEBUG 0
#endif

#if DEBUG
# include <stdio.h>
#endif


int
rsa_generate_keypair(struct rsa_public_key *pub,
		     struct rsa_private_key *key,
		     void *random_ctx, nettle_random_func *random,
		     void *progress_ctx, nettle_progress_func *progress,
		     unsigned n_size,
		     unsigned e_size)
{
  mpz_t p1;
  mpz_t q1;
  mpz_t phi;
  mpz_t tmp;

  if (e_size)
    {
      /* We should choose e randomly. Is the size reasonable? */
      if ((e_size < 16) || (e_size >= n_size) )
	return 0;
    }
  else
    {
      /* We have a fixed e. Check that it makes sense */

      /* It must be odd */
      if (!mpz_tstbit(pub->e, 0))
	return 0;

      /* And 3 or larger */
      if (mpz_cmp_ui(pub->e, 3) < 0)
	return 0;

      /* And size less than n */
      if (mpz_sizeinbase(pub->e, 2) >= n_size)
	return 0;
    }

  if (n_size < RSA_MINIMUM_N_BITS)
    return 0;
  
  mpz_init(p1); mpz_init(q1); mpz_init(phi); mpz_init(tmp);

  /* Generate primes */
  for (;;)
    {
      /* Generate p, such that gcd(p-1, e) = 1 */
      for (;;)
	{
	  nettle_random_prime(key->p, (n_size+1)/2, 1,
			      random_ctx, random,
			      progress_ctx, progress);

	  mpz_sub_ui(p1, key->p, 1);
      
	  /* If e was given, we must chose p such that p-1 has no factors in
	   * common with e. */
	  if (e_size)
	    break;
	  
	  mpz_gcd(tmp, pub->e, p1);

	  if (mpz_cmp_ui(tmp, 1) == 0)
	    break;
	  else if (progress) progress(progress_ctx, 'c');
	} 

      if (progress)
	progress(progress_ctx, '\n');
      
      /* Generate q, such that gcd(q-1, e) = 1 */
      for (;;)
	{
	  nettle_random_prime(key->q, n_size/2, 1,
			      random_ctx, random,
			      progress_ctx, progress);

	  /* Very unlikely. */
	  if (mpz_cmp (key->q, key->p) == 0)
	    continue;

	  mpz_sub_ui(q1, key->q, 1);
      
	  /* If e was given, we must chose q such that q-1 has no factors in
	   * common with e. */
	  if (e_size)
	    break;
	  
	  mpz_gcd(tmp, pub->e, q1);

	  if (mpz_cmp_ui(tmp, 1) == 0)
	    break;
	  else if (progress) progress(progress_ctx, 'c');
	}

      /* Now we have the primes. Is the product of the right size? */
      mpz_mul(pub->n, key->p, key->q);

      assert (mpz_sizeinbase(pub->n, 2) == n_size);

      if (progress)
	progress(progress_ctx, '\n');

      /* c = q^{-1} (mod p) */
      if (mpz_invert(key->c, key->q, key->p))
	/* This should succeed everytime. But if it doesn't,
	 * we try again. */
	break;
      else if (progress) progress(progress_ctx, '?');
    }

  mpz_mul(phi, p1, q1);
  
  /* If we didn't have a given e, generate one now. */
  if (e_size)
    {
      int retried = 0;
      for (;;)
	{
	  nettle_mpz_random_size(pub->e,
				 random_ctx, random,
				 e_size);
	
	  /* Make sure it's odd and that the most significant bit is
	   * set */
	  mpz_setbit(pub->e, 0);
	  mpz_setbit(pub->e, e_size - 1);

	  /* Needs gmp-3, or inverse might be negative. */
	  if (mpz_invert(key->d, pub->e, phi))
	    break;

	  if (progress) progress(progress_ctx, 'e');
	  retried = 1;
	}
      if (retried && progress)
	progress(progress_ctx, '\n');	
    }
  else
    {
      /* Must always succeed, as we already that e
       * doesn't have any common factor with p-1 or q-1. */
      int res = mpz_invert(key->d, pub->e, phi);
      assert(res);
    }

  /* Done! Almost, we must compute the auxillary private values. */
  /* a = d % (p-1) */
  mpz_fdiv_r(key->a, key->d, p1);

  /* b = d % (q-1) */
  mpz_fdiv_r(key->b, key->d, q1);

  /* c was computed earlier */

  pub->size = key->size = (n_size + 7) / 8;
  assert(pub->size >= RSA_MINIMUM_N_OCTETS);
  
  mpz_clear(p1); mpz_clear(q1); mpz_clear(phi); mpz_clear(tmp);

  return 1;
}