1 /* crypto/bn/bn_prime.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
58 /* ====================================================================
59 * Copyright (c) 1998-2001 The OpenSSL Project. All rights reserved.
61 * Redistribution and use in source and binary forms, with or without
62 * modification, are permitted provided that the following conditions
65 * 1. Redistributions of source code must retain the above copyright
66 * notice, this list of conditions and the following disclaimer.
68 * 2. Redistributions in binary form must reproduce the above copyright
69 * notice, this list of conditions and the following disclaimer in
70 * the documentation and/or other materials provided with the
73 * 3. All advertising materials mentioning features or use of this
74 * software must display the following acknowledgment:
75 * "This product includes software developed by the OpenSSL Project
76 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
78 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
79 * endorse or promote products derived from this software without
80 * prior written permission. For written permission, please contact
81 * openssl-core@openssl.org.
83 * 5. Products derived from this software may not be called "OpenSSL"
84 * nor may "OpenSSL" appear in their names without prior written
85 * permission of the OpenSSL Project.
87 * 6. Redistributions of any form whatsoever must retain the following
89 * "This product includes software developed by the OpenSSL Project
90 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
92 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
93 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
94 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
95 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
96 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
97 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
98 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
99 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
100 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
101 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
102 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
103 * OF THE POSSIBILITY OF SUCH DAMAGE.
104 * ====================================================================
106 * This product includes cryptographic software written by Eric Young
107 * (eay@cryptsoft.com). This product includes software written by Tim
108 * Hudson (tjh@cryptsoft.com).
114 #include "cryptlib.h"
116 #include <openssl/rand.h>
118 /* NB: these functions have been "upgraded", the deprecated versions (which are
119 * compatibility wrappers using these functions) are in bn_depr.c.
123 /* The quick sieve algorithm approach to weeding out primes is
124 * Philip Zimmermann's, as implemented in PGP. I have had a read of
125 * his comments and implemented my own version.
127 #include "bn_prime.h"
129 static int witness(BIGNUM *w, const BIGNUM *a, const BIGNUM *a1,
130 const BIGNUM *a1_odd, int k, BN_CTX *ctx, BN_MONT_CTX *mont);
131 static int probable_prime(BIGNUM *rnd, int bits);
132 static int probable_prime_dh(BIGNUM *rnd, const BIGNUM *add,
133 const BIGNUM *rem, BN_CTX *ctx, int first_prime_index);
134 static int probable_prime_dh_safe(BIGNUM *rnd, int bits,
135 const BIGNUM *add, const BIGNUM *rem, BN_CTX *ctx);
137 static int prime_offsets[8] = { 7, 11, 13, 17, 19, 23, 29, 31 };
139 int BN_GENCB_call(BN_GENCB *cb, int a, int b)
141 /* No callback means continue */
146 /* Deprecated-style callbacks */
149 cb->cb.cb_1(a, b, cb->arg);
152 /* New-style callbacks */
153 return cb->cb.cb_2(a, b, cb);
157 /* Unrecognised callback type */
161 int BN_generate_prime_ex(BIGNUM *ret, int bits, int safe,
162 const BIGNUM *add, const BIGNUM *rem, BN_GENCB *cb)
168 int checks = BN_prime_checks_for_size(bits);
172 /* There are no prime numbers this small. */
173 BNerr(BN_F_BN_GENERATE_PRIME_EX, BN_R_BITS_TOO_SMALL);
176 else if (bits == 2 && safe)
178 /* The smallest safe prime (7) is three bits. */
179 BNerr(BN_F_BN_GENERATE_PRIME_EX, BN_R_BITS_TOO_SMALL);
184 if (ctx == NULL) goto err;
189 /* make a random number and set the top and bottom bits */
192 if (!probable_prime(ret,bits)) goto err;
198 if (!probable_prime_dh_safe(ret,bits,add,rem,ctx))
203 if (!bn_probable_prime_dh(ret,bits,add,rem,ctx))
207 /* if (BN_mod_word(ret,(BN_ULONG)3) == 1) goto loop; */
208 if(!BN_GENCB_call(cb, 0, c1++))
214 i=BN_is_prime_fasttest_ex(ret,checks,ctx,0,cb);
215 if (i == -1) goto err;
216 if (i == 0) goto loop;
220 /* for "safe prime" generation,
221 * check that (p-1)/2 is prime.
222 * Since a prime is odd, We just
223 * need to divide by 2 */
224 if (!BN_rshift1(t,ret)) goto err;
226 for (i=0; i<checks; i++)
228 j=BN_is_prime_fasttest_ex(ret,1,ctx,0,cb);
229 if (j == -1) goto err;
230 if (j == 0) goto loop;
232 j=BN_is_prime_fasttest_ex(t,1,ctx,0,cb);
233 if (j == -1) goto err;
234 if (j == 0) goto loop;
236 if(!BN_GENCB_call(cb, 2, c1-1))
238 /* We have a safe prime test pass */
241 /* we have a prime :-) */
253 int BN_is_prime_ex(const BIGNUM *a, int checks, BN_CTX *ctx_passed, BN_GENCB *cb)
255 return BN_is_prime_fasttest_ex(a, checks, ctx_passed, 0, cb);
258 int BN_is_prime_fasttest_ex(const BIGNUM *a, int checks, BN_CTX *ctx_passed,
259 int do_trial_division, BN_GENCB *cb)
264 BIGNUM *A1, *A1_odd, *check; /* taken from ctx */
265 BN_MONT_CTX *mont = NULL;
266 const BIGNUM *A = NULL;
268 if (BN_cmp(a, BN_value_one()) <= 0)
271 if (checks == BN_prime_checks)
272 checks = BN_prime_checks_for_size(BN_num_bits(a));
274 /* first look for small factors */
276 /* a is even => a is prime if and only if a == 2 */
277 return BN_is_word(a, 2);
278 if (do_trial_division)
280 for (i = 1; i < NUMPRIMES; i++)
281 if (BN_mod_word(a, primes[i]) == 0)
283 if(!BN_GENCB_call(cb, 1, -1))
287 if (ctx_passed != NULL)
290 if ((ctx=BN_CTX_new()) == NULL)
298 if ((t = BN_CTX_get(ctx)) == NULL) goto err;
305 A1 = BN_CTX_get(ctx);
306 A1_odd = BN_CTX_get(ctx);
307 check = BN_CTX_get(ctx);
308 if (check == NULL) goto err;
310 /* compute A1 := A - 1 */
313 if (!BN_sub_word(A1, 1))
321 /* write A1 as A1_odd * 2^k */
323 while (!BN_is_bit_set(A1, k))
325 if (!BN_rshift(A1_odd, A1, k))
328 /* Montgomery setup for computations mod A */
329 mont = BN_MONT_CTX_new();
332 if (!BN_MONT_CTX_set(mont, A, ctx))
335 for (i = 0; i < checks; i++)
337 if (!BN_pseudo_rand_range(check, A1))
339 if (!BN_add_word(check, 1))
341 /* now 1 <= check < A */
343 j = witness(check, A, A1, A1_odd, k, ctx, mont);
344 if (j == -1) goto err;
350 if(!BN_GENCB_call(cb, 1, i))
358 if (ctx_passed == NULL)
362 BN_MONT_CTX_free(mont);
367 int bn_probable_prime_dh(BIGNUM *rnd, int bits,
368 const BIGNUM *add, const BIGNUM *rem, BN_CTX *ctx)
370 if (!BN_rand(rnd, bits, 0, 1)) return(0);
372 return(probable_prime_dh(rnd, add, rem, ctx, 1));
375 int bn_probable_prime_dh_coprime(BIGNUM *rnd, int bits,
376 const BIGNUM *add, const BIGNUM *rem, BN_CTX *ctx)
378 BIGNUM *offset_index = BN_new();
380 if (!BN_rand(rnd, bits, 0, 1)) return(0);
381 if (!BN_rand(offset_index, 3, -1, -1)) return(0);
383 BN_mul_word(rnd, 30);
384 BN_add_word(rnd, prime_offsets[BN_get_word(offset_index)]);
386 BN_free(offset_index);
388 return(probable_prime_dh(rnd, add, rem, ctx, 3));
391 static int witness(BIGNUM *w, const BIGNUM *a, const BIGNUM *a1,
392 const BIGNUM *a1_odd, int k, BN_CTX *ctx, BN_MONT_CTX *mont)
394 if (!BN_mod_exp_mont(w, w, a1_odd, a, ctx, mont)) /* w := w^a1_odd mod a */
397 return 0; /* probably prime */
398 if (BN_cmp(w, a1) == 0)
399 return 0; /* w == -1 (mod a), 'a' is probably prime */
402 if (!BN_mod_mul(w, w, w, a, ctx)) /* w := w^2 mod a */
405 return 1; /* 'a' is composite, otherwise a previous 'w' would
406 * have been == -1 (mod 'a') */
407 if (BN_cmp(w, a1) == 0)
408 return 0; /* w == -1 (mod a), 'a' is probably prime */
410 /* If we get here, 'w' is the (a-1)/2-th power of the original 'w',
411 * and it is neither -1 nor +1 -- so 'a' cannot be prime */
416 static int probable_prime(BIGNUM *rnd, int bits)
419 prime_t mods[NUMPRIMES];
421 BN_ULONG maxdelta = BN_MASK2 - primes[NUMPRIMES-1];
422 char is_single_word = bits <= BN_BITS2;
425 if (!BN_rand(rnd,bits,1,1)) return(0);
426 /* we now have a random number 'rnd' to test. */
427 for (i=1; i<NUMPRIMES; i++)
428 mods[i]=(prime_t)BN_mod_word(rnd,(BN_ULONG)primes[i]);
429 /* If bits is so small that it fits into a single word then we
430 * additionally don't want to exceed that many bits. */
433 BN_ULONG size_limit = (((BN_ULONG) 1) << bits) - BN_get_word(rnd) - 1;
434 if (size_limit < maxdelta)
435 maxdelta = size_limit;
441 BN_ULONG rnd_word = BN_get_word(rnd);
443 /* In the case that the candidate prime is a single word then
445 * 1) It's greater than primes[i] because we shouldn't reject
446 * 3 as being a prime number because it's a multiple of
448 * 2) That it's not a multiple of a known prime. We don't
449 * check that rnd-1 is also coprime to all the known
450 * primes because there aren't many small primes where
452 for (i=1; i<NUMPRIMES && primes[i]<rnd_word; i++)
454 if ((mods[i]+delta)%primes[i] == 0)
457 if (delta > maxdelta) goto again;
464 for (i=1; i<NUMPRIMES; i++)
466 /* check that rnd is not a prime and also
467 * that gcd(rnd-1,primes) == 1 (except for 2) */
468 if (((mods[i]+delta)%primes[i]) <= 1)
471 if (delta > maxdelta) goto again;
476 if (!BN_add_word(rnd,delta)) return(0);
477 if (BN_num_bits(rnd) != bits)
483 static int probable_prime_dh(BIGNUM *rnd, const BIGNUM *add,
484 const BIGNUM *rem, BN_CTX *ctx, int first_prime_index)
490 if ((t1 = BN_CTX_get(ctx)) == NULL) goto err;
492 /* we need ((rnd-rem) % add) == 0 */
494 if (!BN_mod(t1,rnd,add,ctx)) goto err;
495 if (!BN_sub(rnd,rnd,t1)) goto err;
497 { if (!BN_add_word(rnd,1)) goto err; }
499 { if (!BN_add(rnd,rnd,rem)) goto err; }
501 /* we now have a random number 'rand' to test. */
504 for (i=first_prime_index; i<NUMPRIMES; i++)
506 /* check that rnd is a prime */
507 if (BN_mod_word(rnd,(BN_ULONG)primes[i]) <= 1)
509 if (!BN_add(rnd,rnd,add)) goto err;
520 static int probable_prime_dh_safe(BIGNUM *p, int bits, const BIGNUM *padd,
521 const BIGNUM *rem, BN_CTX *ctx)
528 t1 = BN_CTX_get(ctx);
530 qadd = BN_CTX_get(ctx);
531 if (qadd == NULL) goto err;
533 if (!BN_rshift1(qadd,padd)) goto err;
535 if (!BN_rand(q,bits,0,1)) goto err;
537 /* we need ((rnd-rem) % add) == 0 */
538 if (!BN_mod(t1,q,qadd,ctx)) goto err;
539 if (!BN_sub(q,q,t1)) goto err;
541 { if (!BN_add_word(q,1)) goto err; }
544 if (!BN_rshift1(t1,rem)) goto err;
545 if (!BN_add(q,q,t1)) goto err;
548 /* we now have a random number 'rand' to test. */
549 if (!BN_lshift1(p,q)) goto err;
550 if (!BN_add_word(p,1)) goto err;
553 for (i=1; i<NUMPRIMES; i++)
555 /* check that p and q are prime */
556 /* check that for p and q
557 * gcd(p-1,primes) == 1 (except for 2) */
558 if ( (BN_mod_word(p,(BN_ULONG)primes[i]) == 0) ||
559 (BN_mod_word(q,(BN_ULONG)primes[i]) == 0))
561 if (!BN_add(p,p,padd)) goto err;
562 if (!BN_add(q,q,qadd)) goto err;