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.]
63 #include <openssl/rand.h>
65 /* The quick sieve algorithm approach to weeding out primes is
66 * Philip Zimmermann's, as implemented in PGP. I have had a read of
67 * his comments and implemented my own version.
71 static int witness(BIGNUM *w, BIGNUM *a, BIGNUM *a1, BIGNUM *a1_odd, int k,
72 BN_CTX *ctx, BN_MONT_CTX *mont);
73 static int probable_prime(BIGNUM *rnd, int bits);
74 static int probable_prime_dh(BIGNUM *rnd, int bits,
75 BIGNUM *add, BIGNUM *rem, BN_CTX *ctx);
76 static int probable_prime_dh_safe(BIGNUM *rnd, int bits,
77 BIGNUM *add, BIGNUM *rem, BN_CTX *ctx);
79 BIGNUM *BN_generate_prime(BIGNUM *ret, int bits, int safe, BIGNUM *add,
80 BIGNUM *rem, void (*callback)(int,int,void *), void *cb_arg)
87 int checks = BN_prime_checks_for_size(bits);
90 if (ctx == NULL) goto err;
93 if ((rnd=BN_new()) == NULL) goto err;
99 /* make a random number and set the top and bottom bits */
102 if (!probable_prime(rnd,bits)) goto err;
108 if (!probable_prime_dh_safe(rnd,bits,add,rem,ctx))
113 if (!probable_prime_dh(rnd,bits,add,rem,ctx))
117 /* if (BN_mod_word(rnd,(BN_ULONG)3) == 1) goto loop; */
118 if (callback != NULL) callback(0,c1++,cb_arg);
122 i=BN_is_prime_fasttest(rnd,checks,callback,ctx,cb_arg,0);
123 if (i == -1) goto err;
124 if (i == 0) goto loop;
128 /* for "safe prime" generation,
129 * check that (p-1)/2 is prime.
130 * Since a prime is odd, We just
131 * need to divide by 2 */
132 if (!BN_rshift1(&t,rnd)) goto err;
134 for (i=0; i<checks; i++)
136 j=BN_is_prime_fasttest(rnd,1,callback,ctx,cb_arg,0);
137 if (j == -1) goto err;
138 if (j == 0) goto loop;
140 j=BN_is_prime_fasttest(&t,1,callback,ctx,cb_arg,0);
141 if (j == -1) goto err;
142 if (j == 0) goto loop;
144 if (callback != NULL) callback(2,c1-1,cb_arg);
145 /* We have a safe prime test pass */
148 /* we have a prime :-) */
151 if (!found && (ret == NULL) && (rnd != NULL)) BN_free(rnd);
153 if (ctx != NULL) BN_CTX_free(ctx);
154 return(found ? rnd : NULL);
157 int BN_is_prime(BIGNUM *a, int checks, void (*callback)(int,int,void *),
158 BN_CTX *ctx_passed, void *cb_arg)
160 return BN_is_prime_fasttest(a, checks, callback, ctx_passed, cb_arg, 0);
163 int BN_is_prime_fasttest(BIGNUM *a, int checks,
164 void (*callback)(int,int,void *),
165 BN_CTX *ctx_passed, void *cb_arg,
166 int do_trial_division)
171 BIGNUM *a1, *a1_odd, *check; /* taken from ctx */
172 BN_MONT_CTX *mont = NULL;
174 if (checks == BN_prime_checks)
175 checks = BN_prime_checks_for_size(BN_num_bits(a));
177 if (a->neg) /* for now, refuse to handle negative numbers */
180 /* first look for small factors */
183 if (do_trial_division)
185 for (i = 1; i < NUMPRIMES; i++)
186 if (BN_mod_word(a, primes[i]) == 0)
188 if (callback != NULL) callback(1, -1, cb_arg);
191 if (ctx_passed != NULL)
194 if ((ctx=BN_CTX_new()) == NULL)
196 a1 = &(ctx->bn[ctx->tos++]);
197 a1_odd = &(ctx->bn[ctx->tos++]);
198 check = &(ctx->bn[ctx->tos++]);;
200 /* compute a1 := a - 1 */
203 if (!BN_sub_word(a1, 1))
211 /* write a1 as a1_odd * 2^k */
213 while (!BN_is_bit_set(a1, k))
215 if (!BN_rshift(a1_odd, a1, k))
218 /* Montgomery setup for computations mod a */
219 mont = BN_MONT_CTX_new();
222 if (!BN_MONT_CTX_set(mont, a, ctx))
225 for (i = 0; i < checks; i++)
227 if (!BN_pseudo_rand(check, BN_num_bits(a1), 0, 0))
229 if (BN_cmp(check, a1) >= 0)
230 if (!BN_sub(check, check, a1))
232 if (!BN_add_word(check, 1))
234 /* now 1 <= check < a */
236 j = witness(check, a, a1, a1_odd, k, ctx, mont);
237 if (j == -1) goto err;
243 if (callback != NULL) callback(1,i,cb_arg);
247 if (ctx_passed != NULL)
248 ctx_passed->tos -= 3; /* a1, a1_odd, check */
249 else if (ctx != NULL)
252 BN_MONT_CTX_free(mont);
257 static int witness(BIGNUM *w, BIGNUM *a, BIGNUM *a1, BIGNUM *a1_odd, int k,
258 BN_CTX *ctx, BN_MONT_CTX *mont)
260 if (!BN_mod_exp_mont(w, w, a1_odd, a, ctx, mont)) /* w := w^a1_odd mod a */
263 return 0; /* probably prime */
264 if (BN_cmp(w, a1) == 0)
265 return 0; /* w == -1 (mod a), 'a' is probably prime */
268 if (!BN_mod_mul(w, w, w, a, ctx)) /* w := w^2 mod a */
271 return 1; /* 'a' is composite, otherwise a previous 'w' would
272 * have been == -1 (mod 'a') */
273 if (BN_cmp(w, a1) == 0)
274 return 0; /* w == -1 (mod a), 'a' is probably prime */
276 /* If we get here, 'w' is the (a-1)/2-th power of the original 'w',
277 * and it is neither -1 nor +1 -- so 'a' cannot be prime */
281 static int probable_prime(BIGNUM *rnd, int bits)
284 BN_ULONG mods[NUMPRIMES];
288 if (!BN_rand(rnd,bits,1,1)) return(0);
289 /* we now have a random number 'rand' to test. */
290 for (i=1; i<NUMPRIMES; i++)
291 mods[i]=BN_mod_word(rnd,(BN_ULONG)primes[i]);
293 loop: for (i=1; i<NUMPRIMES; i++)
295 /* check that rnd is not a prime and also
296 * that gcd(rnd-1,primes) == 1 (except for 2) */
297 if (((mods[i]+delta)%primes[i]) <= 1)
301 /* perhaps need to check for overflow of
302 * delta (but delta can be upto 2^32)
303 * 21-May-98 eay - added overflow check */
304 if (delta < d) goto again;
308 if (!BN_add_word(rnd,delta)) return(0);
312 static int probable_prime_dh(BIGNUM *rnd, int bits, BIGNUM *add, BIGNUM *rem,
318 t1= &(ctx->bn[ctx->tos++]);
320 if (!BN_rand(rnd,bits,0,1)) goto err;
322 /* we need ((rnd-rem) % add) == 0 */
324 if (!BN_mod(t1,rnd,add,ctx)) goto err;
325 if (!BN_sub(rnd,rnd,t1)) goto err;
327 { if (!BN_add_word(rnd,1)) goto err; }
329 { if (!BN_add(rnd,rnd,rem)) goto err; }
331 /* we now have a random number 'rand' to test. */
333 loop: for (i=1; i<NUMPRIMES; i++)
335 /* check that rnd is a prime */
336 if (BN_mod_word(rnd,(BN_ULONG)primes[i]) <= 1)
338 if (!BN_add(rnd,rnd,add)) goto err;
348 static int probable_prime_dh_safe(BIGNUM *p, int bits, BIGNUM *padd,
349 BIGNUM *rem, BN_CTX *ctx)
352 BIGNUM *t1,*qadd=NULL,*q=NULL;
355 t1= &(ctx->bn[ctx->tos++]);
356 q= &(ctx->bn[ctx->tos++]);
357 qadd= &(ctx->bn[ctx->tos++]);
359 if (!BN_rshift1(qadd,padd)) goto err;
361 if (!BN_rand(q,bits,0,1)) goto err;
363 /* we need ((rnd-rem) % add) == 0 */
364 if (!BN_mod(t1,q,qadd,ctx)) goto err;
365 if (!BN_sub(q,q,t1)) goto err;
367 { if (!BN_add_word(q,1)) goto err; }
370 if (!BN_rshift1(t1,rem)) goto err;
371 if (!BN_add(q,q,t1)) goto err;
374 /* we now have a random number 'rand' to test. */
375 if (!BN_lshift1(p,q)) goto err;
376 if (!BN_add_word(p,1)) goto err;
378 loop: for (i=1; i<NUMPRIMES; i++)
380 /* check that p and q are prime */
381 /* check that for p and q
382 * gcd(p-1,primes) == 1 (except for 2) */
383 if ( (BN_mod_word(p,(BN_ULONG)primes[i]) == 0) ||
384 (BN_mod_word(q,(BN_ULONG)primes[i]) == 0))
386 if (!BN_add(p,p,padd)) goto err;
387 if (!BN_add(q,q,qadd)) goto err;