sl@0: /* crypto/dh/dh_gen.c */ sl@0: /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) sl@0: * All rights reserved. sl@0: * sl@0: * This package is an SSL implementation written sl@0: * by Eric Young (eay@cryptsoft.com). sl@0: * The implementation was written so as to conform with Netscapes SSL. sl@0: * sl@0: * This library is free for commercial and non-commercial use as long as sl@0: * the following conditions are aheared to. The following conditions sl@0: * apply to all code found in this distribution, be it the RC4, RSA, sl@0: * lhash, DES, etc., code; not just the SSL code. The SSL documentation sl@0: * included with this distribution is covered by the same copyright terms sl@0: * except that the holder is Tim Hudson (tjh@cryptsoft.com). sl@0: * sl@0: * Copyright remains Eric Young's, and as such any Copyright notices in sl@0: * the code are not to be removed. sl@0: * If this package is used in a product, Eric Young should be given attribution sl@0: * as the author of the parts of the library used. sl@0: * This can be in the form of a textual message at program startup or sl@0: * in documentation (online or textual) provided with the package. sl@0: * sl@0: * Redistribution and use in source and binary forms, with or without sl@0: * modification, are permitted provided that the following conditions sl@0: * are met: sl@0: * 1. Redistributions of source code must retain the copyright sl@0: * notice, this list of conditions and the following disclaimer. sl@0: * 2. Redistributions in binary form must reproduce the above copyright sl@0: * notice, this list of conditions and the following disclaimer in the sl@0: * documentation and/or other materials provided with the distribution. sl@0: * 3. All advertising materials mentioning features or use of this software sl@0: * must display the following acknowledgement: sl@0: * "This product includes cryptographic software written by sl@0: * Eric Young (eay@cryptsoft.com)" sl@0: * The word 'cryptographic' can be left out if the rouines from the library sl@0: * being used are not cryptographic related :-). sl@0: * 4. If you include any Windows specific code (or a derivative thereof) from sl@0: * the apps directory (application code) you must include an acknowledgement: sl@0: * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" sl@0: * sl@0: * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND sl@0: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE sl@0: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE sl@0: * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE sl@0: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL sl@0: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS sl@0: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) sl@0: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT sl@0: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY sl@0: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF sl@0: * SUCH DAMAGE. sl@0: * sl@0: * The licence and distribution terms for any publically available version or sl@0: * derivative of this code cannot be changed. i.e. this code cannot simply be sl@0: * copied and put under another distribution licence sl@0: * [including the GNU Public Licence.] sl@0: */ sl@0: sl@0: /* NB: These functions have been upgraded - the previous prototypes are in sl@0: * dh_depr.c as wrappers to these ones. sl@0: * - Geoff sl@0: */ sl@0: sl@0: #include sl@0: #include "cryptlib.h" sl@0: #include sl@0: #include sl@0: sl@0: static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb); sl@0: sl@0: EXPORT_C int DH_generate_parameters_ex(DH *ret, int prime_len, int generator, BN_GENCB *cb) sl@0: { sl@0: if(ret->meth->generate_params) sl@0: return ret->meth->generate_params(ret, prime_len, generator, cb); sl@0: return dh_builtin_genparams(ret, prime_len, generator, cb); sl@0: } sl@0: sl@0: /* We generate DH parameters as follows sl@0: * find a prime q which is prime_len/2 bits long. sl@0: * p=(2*q)+1 or (p-1)/2 = q sl@0: * For this case, g is a generator if sl@0: * g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1. sl@0: * Since the factors of p-1 are q and 2, we just need to check sl@0: * g^2 mod p != 1 and g^q mod p != 1. sl@0: * sl@0: * Having said all that, sl@0: * there is another special case method for the generators 2, 3 and 5. sl@0: * for 2, p mod 24 == 11 sl@0: * for 3, p mod 12 == 5 <<<<< does not work for safe primes. sl@0: * for 5, p mod 10 == 3 or 7 sl@0: * sl@0: * Thanks to Phil Karn for the pointers about the sl@0: * special generators and for answering some of my questions. sl@0: * sl@0: * I've implemented the second simple method :-). sl@0: * Since DH should be using a safe prime (both p and q are prime), sl@0: * this generator function can take a very very long time to run. sl@0: */ sl@0: /* Actually there is no reason to insist that 'generator' be a generator. sl@0: * It's just as OK (and in some sense better) to use a generator of the sl@0: * order-q subgroup. sl@0: */ sl@0: static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb) sl@0: { sl@0: BIGNUM *t1,*t2; sl@0: int g,ok= -1; sl@0: BN_CTX *ctx=NULL; sl@0: sl@0: ctx=BN_CTX_new(); sl@0: if (ctx == NULL) goto err; sl@0: BN_CTX_start(ctx); sl@0: t1 = BN_CTX_get(ctx); sl@0: t2 = BN_CTX_get(ctx); sl@0: if (t1 == NULL || t2 == NULL) goto err; sl@0: sl@0: /* Make sure 'ret' has the necessary elements */ sl@0: if(!ret->p && ((ret->p = BN_new()) == NULL)) goto err; sl@0: if(!ret->g && ((ret->g = BN_new()) == NULL)) goto err; sl@0: sl@0: if (generator <= 1) sl@0: { sl@0: DHerr(DH_F_DH_BUILTIN_GENPARAMS, DH_R_BAD_GENERATOR); sl@0: goto err; sl@0: } sl@0: if (generator == DH_GENERATOR_2) sl@0: { sl@0: if (!BN_set_word(t1,24)) goto err; sl@0: if (!BN_set_word(t2,11)) goto err; sl@0: g=2; sl@0: } sl@0: #if 0 /* does not work for safe primes */ sl@0: else if (generator == DH_GENERATOR_3) sl@0: { sl@0: if (!BN_set_word(t1,12)) goto err; sl@0: if (!BN_set_word(t2,5)) goto err; sl@0: g=3; sl@0: } sl@0: #endif sl@0: else if (generator == DH_GENERATOR_5) sl@0: { sl@0: if (!BN_set_word(t1,10)) goto err; sl@0: if (!BN_set_word(t2,3)) goto err; sl@0: /* BN_set_word(t3,7); just have to miss sl@0: * out on these ones :-( */ sl@0: g=5; sl@0: } sl@0: else sl@0: { sl@0: /* in the general case, don't worry if 'generator' is a sl@0: * generator or not: since we are using safe primes, sl@0: * it will generate either an order-q or an order-2q group, sl@0: * which both is OK */ sl@0: if (!BN_set_word(t1,2)) goto err; sl@0: if (!BN_set_word(t2,1)) goto err; sl@0: g=generator; sl@0: } sl@0: sl@0: if(!BN_generate_prime_ex(ret->p,prime_len,1,t1,t2,cb)) goto err; sl@0: if(!BN_GENCB_call(cb, 3, 0)) goto err; sl@0: if (!BN_set_word(ret->g,g)) goto err; sl@0: ok=1; sl@0: err: sl@0: if (ok == -1) sl@0: { sl@0: DHerr(DH_F_DH_BUILTIN_GENPARAMS,ERR_R_BN_LIB); sl@0: ok=0; sl@0: } sl@0: sl@0: if (ctx != NULL) sl@0: { sl@0: BN_CTX_end(ctx); sl@0: BN_CTX_free(ctx); sl@0: } sl@0: return ok; sl@0: }