crypto/bn/bn_x931p.c

   1 /*
   2  * Copyright 2011-2018 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include <stdio.h>
  11 #include <openssl/bn.h>
  12 #include "bn_local.h"
  13
  14 /* X9.31 routines for prime derivation */
  15
  16 /*
  17  * X9.31 prime derivation. This is used to generate the primes pi (p1, p2,
  18  * q1, q2) from a parameter Xpi by checking successive odd integers.
  19  */
  20
  21 static int bn_x931_derive_pi(BIGNUM *pi, const BIGNUM *Xpi, BN_CTX *ctx,
  22                              BN_GENCB *cb)
  23 {
  24     int i = 0, is_prime;
  25     if (!BN_copy(pi, Xpi))
  26         return 0;
  27     if (!BN_is_odd(pi) && !BN_add_word(pi, 1))
  28         return 0;
  29     for (;;) {
  30         i++;
  31         BN_GENCB_call(cb, 0, i);
  32         /* NB 27 MR is specified in X9.31 */
  33         is_prime = BN_check_prime(pi, ctx, cb);
  34         if (is_prime < 0)
  35             return 0;
  36         if (is_prime)
  37             break;
  38         if (!BN_add_word(pi, 2))
  39             return 0;
  40     }
  41     BN_GENCB_call(cb, 2, i);
  42     return 1;
  43 }
  44
  45 /*
  46  * This is the main X9.31 prime derivation function. From parameters Xp1, Xp2
  47  * and Xp derive the prime p. If the parameters p1 or p2 are not NULL they
  48  * will be returned too: this is needed for testing.
  49  */
  50
  51 int BN_X931_derive_prime_ex(BIGNUM *p, BIGNUM *p1, BIGNUM *p2,
  52                             const BIGNUM *Xp, const BIGNUM *Xp1,
  53                             const BIGNUM *Xp2, const BIGNUM *e, BN_CTX *ctx,
  54                             BN_GENCB *cb)
  55 {
  56     int ret = 0;
  57
  58     BIGNUM *t, *p1p2, *pm1;
  59
  60     /* Only even e supported */
  61     if (!BN_is_odd(e))
  62         return 0;
  63
  64     BN_CTX_start(ctx);
  65     if (p1 == NULL)
  66         p1 = BN_CTX_get(ctx);
  67
  68     if (p2 == NULL)
  69         p2 = BN_CTX_get(ctx);
  70
  71     t = BN_CTX_get(ctx);
  72
  73     p1p2 = BN_CTX_get(ctx);
  74
  75     pm1 = BN_CTX_get(ctx);
  76
  77     if (pm1 == NULL)
  78         goto err;
  79
  80     if (!bn_x931_derive_pi(p1, Xp1, ctx, cb))
  81         goto err;
  82
  83     if (!bn_x931_derive_pi(p2, Xp2, ctx, cb))
  84         goto err;
  85
  86     if (!BN_mul(p1p2, p1, p2, ctx))
  87         goto err;
  88
  89     /* First set p to value of Rp */
  90
  91     if (!BN_mod_inverse(p, p2, p1, ctx))
  92         goto err;
  93
  94     if (!BN_mul(p, p, p2, ctx))
  95         goto err;
  96
  97     if (!BN_mod_inverse(t, p1, p2, ctx))
  98         goto err;
  99
 100     if (!BN_mul(t, t, p1, ctx))
 101         goto err;
 102
 103     if (!BN_sub(p, p, t))
 104         goto err;
 105
 106     if (p->neg && !BN_add(p, p, p1p2))
 107         goto err;
 108
 109     /* p now equals Rp */
 110
 111     if (!BN_mod_sub(p, p, Xp, p1p2, ctx))
 112         goto err;
 113
 114     if (!BN_add(p, p, Xp))
 115         goto err;
 116
 117     /* p now equals Yp0 */
 118
 119     for (;;) {
 120         int i = 1;
 121         BN_GENCB_call(cb, 0, i++);
 122         if (!BN_copy(pm1, p))
 123             goto err;
 124         if (!BN_sub_word(pm1, 1))
 125             goto err;
 126         if (!BN_gcd(t, pm1, e, ctx))
 127             goto err;
 128         if (BN_is_one(t)) {
 129             /*
 130              * X9.31 specifies 8 MR and 1 Lucas test or any prime test
 131              * offering similar or better guarantees 50 MR is considerably
 132              * better.
 133              */
 134             int r = BN_check_prime(p, ctx, cb);
 135             if (r < 0)
 136                 goto err;
 137             if (r)
 138                 break;
 139         }
 140         if (!BN_add(p, p, p1p2))
 141             goto err;
 142     }
 143
 144     BN_GENCB_call(cb, 3, 0);
 145
 146     ret = 1;
 147
 148  err:
 149
 150     BN_CTX_end(ctx);
 151
 152     return ret;
 153 }
 154
 155 /*
 156  * Generate pair of parameters Xp, Xq for X9.31 prime generation. Note: nbits
 157  * parameter is sum of number of bits in both.
 158  */
 159
 160 int BN_X931_generate_Xpq(BIGNUM *Xp, BIGNUM *Xq, int nbits, BN_CTX *ctx)
 161 {
 162     BIGNUM *t;
 163     int i;
 164     /*
 165      * Number of bits for each prime is of the form 512+128s for s = 0, 1,
 166      * ...
 167      */
 168     if ((nbits < 1024) || (nbits & 0xff))
 169         return 0;
 170     nbits >>= 1;
 171     /*
 172      * The random value Xp must be between sqrt(2) * 2^(nbits-1) and 2^nbits
 173      * - 1. By setting the top two bits we ensure that the lower bound is
 174      * exceeded.
 175      */
 176     if (!BN_priv_rand_ex(Xp, nbits, BN_RAND_TOP_TWO, BN_RAND_BOTTOM_ANY, ctx))
 177         goto err;
 178
 179     BN_CTX_start(ctx);
 180     t = BN_CTX_get(ctx);
 181     if (t == NULL)
 182         goto err;
 183
 184     for (i = 0; i < 1000; i++) {
 185         if (!BN_priv_rand_ex(Xq, nbits, BN_RAND_TOP_TWO, BN_RAND_BOTTOM_ANY,
 186                              ctx))
 187             goto err;
 188
 189         /* Check that |Xp - Xq| > 2^(nbits - 100) */
 190         if (!BN_sub(t, Xp, Xq))
 191             goto err;
 192         if (BN_num_bits(t) > (nbits - 100))
 193             break;
 194     }
 195
 196     BN_CTX_end(ctx);
 197
 198     if (i < 1000)
 199         return 1;
 200
 201     return 0;
 202
 203  err:
 204     BN_CTX_end(ctx);
 205     return 0;
 206 }
 207
 208 /*
 209  * Generate primes using X9.31 algorithm. Of the values p, p1, p2, Xp1 and
 210  * Xp2 only 'p' needs to be non-NULL. If any of the others are not NULL the
 211  * relevant parameter will be stored in it. Due to the fact that |Xp - Xq| >
 212  * 2^(nbits - 100) must be satisfied Xp and Xq are generated using the
 213  * previous function and supplied as input.
 214  */
 215
 216 int BN_X931_generate_prime_ex(BIGNUM *p, BIGNUM *p1, BIGNUM *p2,
 217                               BIGNUM *Xp1, BIGNUM *Xp2,
 218                               const BIGNUM *Xp,
 219                               const BIGNUM *e, BN_CTX *ctx, BN_GENCB *cb)
 220 {
 221     int ret = 0;
 222
 223     BN_CTX_start(ctx);
 224     if (Xp1 == NULL)
 225         Xp1 = BN_CTX_get(ctx);
 226     if (Xp2 == NULL)
 227         Xp2 = BN_CTX_get(ctx);
 228     if (Xp1 == NULL || Xp2 == NULL)
 229         goto error;
 230
 231     if (!BN_priv_rand_ex(Xp1, 101, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY, ctx))
 232         goto error;
 233     if (!BN_priv_rand_ex(Xp2, 101, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY, ctx))
 234         goto error;
 235     if (!BN_X931_derive_prime_ex(p, p1, p2, Xp, Xp1, Xp2, e, ctx, cb))
 236         goto error;
 237
 238     ret = 1;
 239
 240  error:
 241     BN_CTX_end(ctx);
 242
 243     return ret;
 244
 245 }