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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
*/
#include "tomcrypt.h"
/**
@file rsa_make_key.c
RSA key generation, Tom St Denis
*/
#ifdef MRSA
/**
Create an RSA key
@param prng An active PRNG state
@param wprng The index of the PRNG desired
@param size The size of the modulus (key size) desired (octets)
@param e The "e" value (public key). e==65537 is a good choice
@param key [out] Destination of a newly created private key pair
@return CRYPT_OK if successful, upon error all allocated ram is freed
*/
int rsa_make_key(prng_state *prng, int wprng, int size, long e, rsa_key *key)
{
void *p, *q, *tmp1, *tmp2, *tmp3;
int err;
LTC_ARGCHK(ltc_mp.name != NULL);
LTC_ARGCHK(key != NULL);
if ((size < (MIN_RSA_SIZE/8)) || (size > (MAX_RSA_SIZE/8))) {
return CRYPT_INVALID_KEYSIZE;
}
if ((e < 3) || ((e & 1) == 0)) {
return CRYPT_INVALID_ARG;
}
if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
return err;
}
if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, &tmp3, NULL)) != CRYPT_OK) {
return err;
}
/* make primes p and q (optimization provided by Wayne Scott) */
if ((err = mp_set_int(tmp3, e)) != CRYPT_OK) { goto errkey; } /* tmp3 = e */
/* make prime "p" */
do {
if ((err = rand_prime( p, size/2, prng, wprng)) != CRYPT_OK) { goto errkey; }
if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto errkey; } /* tmp1 = p-1 */
if ((err = mp_gcd( tmp1, tmp3, tmp2)) != CRYPT_OK) { goto errkey; } /* tmp2 = gcd(p-1, e) */
} while (mp_cmp_d( tmp2, 1) != 0); /* while e divides p-1 */
/* make prime "q" */
do {
if ((err = rand_prime( q, size/2, prng, wprng)) != CRYPT_OK) { goto errkey; }
if ((err = mp_sub_d( q, 1, tmp1)) != CRYPT_OK) { goto errkey; } /* tmp1 = q-1 */
if ((err = mp_gcd( tmp1, tmp3, tmp2)) != CRYPT_OK) { goto errkey; } /* tmp2 = gcd(q-1, e) */
} while (mp_cmp_d( tmp2, 1) != 0); /* while e divides q-1 */
/* tmp1 = lcm(p-1, q-1) */
if ((err = mp_sub_d( p, 1, tmp2)) != CRYPT_OK) { goto errkey; } /* tmp2 = p-1 */
/* tmp1 = q-1 (previous do/while loop) */
if ((err = mp_lcm( tmp1, tmp2, tmp1)) != CRYPT_OK) { goto errkey; } /* tmp1 = lcm(p-1, q-1) */
/* make key */
if ((err = mp_init_multi(&key->e, &key->d, &key->N, &key->dQ, &key->dP, &key->qP, &key->p, &key->q, NULL)) != CRYPT_OK) {
goto errkey;
}
if ((err = mp_set_int( key->e, e)) != CRYPT_OK) { goto errkey; } /* key->e = e */
if ((err = mp_invmod( key->e, tmp1, key->d)) != CRYPT_OK) { goto errkey; } /* key->d = 1/e mod lcm(p-1,q-1) */
if ((err = mp_mul( p, q, key->N)) != CRYPT_OK) { goto errkey; } /* key->N = pq */
/* optimize for CRT now */
/* find d mod q-1 and d mod p-1 */
if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto errkey; } /* tmp1 = q-1 */
if ((err = mp_sub_d( q, 1, tmp2)) != CRYPT_OK) { goto errkey; } /* tmp2 = p-1 */
if ((err = mp_mod( key->d, tmp1, key->dP)) != CRYPT_OK) { goto errkey; } /* dP = d mod p-1 */
if ((err = mp_mod( key->d, tmp2, key->dQ)) != CRYPT_OK) { goto errkey; } /* dQ = d mod q-1 */
if ((err = mp_invmod( q, p, key->qP)) != CRYPT_OK) { goto errkey; } /* qP = 1/q mod p */
if ((err = mp_copy( p, key->p)) != CRYPT_OK) { goto errkey; }
if ((err = mp_copy( q, key->q)) != CRYPT_OK) { goto errkey; }
/* set key type (in this case it's CRT optimized) */
key->type = PK_PRIVATE;
/* return ok and free temps */
err = CRYPT_OK;
goto cleanup;
errkey:
mp_clear_multi(key->d, key->e, key->N, key->dQ, key->dP, key->qP, key->p, key->q, NULL);
cleanup:
mp_clear_multi(tmp3, tmp2, tmp1, p, q, NULL);
return err;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/pk/rsa/rsa_make_key.c,v $ */
/* $Revision: 1.14 $ */
/* $Date: 2006/12/04 22:23:27 $ */
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