88 lines
1.8 KiB
C
88 lines
1.8 KiB
C
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org
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*/
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#include "tomcrypt.h"
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/**
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@file rand_prime.c
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Generate a random prime, Tom St Denis
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*/
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#define USE_BBS 1
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int rand_prime(void *N, long len, prng_state *prng, int wprng)
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{
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int err, res, type;
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unsigned char *buf;
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LTC_ARGCHK(N != NULL);
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/* get type */
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if (len < 0) {
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type = USE_BBS;
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len = -len;
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} else {
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type = 0;
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}
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/* allow sizes between 2 and 512 bytes for a prime size */
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if (len < 2 || len > 512) {
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return CRYPT_INVALID_PRIME_SIZE;
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}
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/* valid PRNG? Better be! */
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if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
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return err;
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}
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/* allocate buffer to work with */
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buf = XCALLOC(1, len);
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if (buf == NULL) {
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return CRYPT_MEM;
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}
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do {
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/* generate value */
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if (prng_descriptor[wprng].read(buf, len, prng) != (unsigned long)len) {
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XFREE(buf);
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return CRYPT_ERROR_READPRNG;
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}
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/* munge bits */
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buf[0] |= 0x80 | 0x40;
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buf[len-1] |= 0x01 | ((type & USE_BBS) ? 0x02 : 0x00);
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/* load value */
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if ((err = mp_read_unsigned_bin(N, buf, len)) != CRYPT_OK) {
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XFREE(buf);
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return err;
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}
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/* test */
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if ((err = mp_prime_is_prime(N, 8, &res)) != CRYPT_OK) {
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XFREE(buf);
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return err;
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}
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} while (res == LTC_MP_NO);
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#ifdef LTC_CLEAN_STACK
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zeromem(buf, len);
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#endif
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XFREE(buf);
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return CRYPT_OK;
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}
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/* $Source$ */
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/* $Revision$ */
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/* $Date$ */
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