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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.org
*/
#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)
{
mp_int p, q, tmp1, tmp2, tmp3;
int err;
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)) != MP_OKAY) {
return mpi_to_ltc_error(err);
}
/* make primes p and q (optimization provided by Wayne Scott) */
if ((err = mp_set_int(&tmp3, e)) != MP_OKAY) { goto error; } /* tmp3 = e */
/* make prime "p" */
do {
if ((err = rand_prime(&p, size*4, prng, wprng)) != CRYPT_OK) { goto done; }
if ((err = mp_sub_d(&p, 1, &tmp1)) != MP_OKAY) { goto error; } /* tmp1 = p-1 */
if ((err = mp_gcd(&tmp1, &tmp3, &tmp2)) != MP_OKAY) { goto error; } /* 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*4, prng, wprng)) != CRYPT_OK) { goto done; }
if ((err = mp_sub_d(&q, 1, &tmp1)) != MP_OKAY) { goto error; } /* tmp1 = q-1 */
if ((err = mp_gcd(&tmp1, &tmp3, &tmp2)) != MP_OKAY) { goto error; } /* 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)) != MP_OKAY) { goto error; } /* tmp2 = p-1 */
/* tmp1 = q-1 (previous do/while loop) */
if ((err = mp_lcm(&tmp1, &tmp2, &tmp1)) != MP_OKAY) { goto error; } /* 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)) != MP_OKAY) {
goto error;
}
if ((err = mp_set_int(&key->e, e)) != MP_OKAY) { goto error2; } /* key->e = e */
if ((err = mp_invmod(&key->e, &tmp1, &key->d)) != MP_OKAY) { goto error2; } /* key->d = 1/e mod lcm(p-1,q-1) */
if ((err = mp_mul(&p, &q, &key->N)) != MP_OKAY) { goto error2; } /* 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)) != MP_OKAY) { goto error2; } /* tmp1 = q-1 */
if ((err = mp_sub_d(&q, 1, &tmp2)) != MP_OKAY) { goto error2; } /* tmp2 = p-1 */
if ((err = mp_mod(&key->d, &tmp1, &key->dP)) != MP_OKAY) { goto error2; } /* dP = d mod p-1 */
if ((err = mp_mod(&key->d, &tmp2, &key->dQ)) != MP_OKAY) { goto error2; } /* dQ = d mod q-1 */
if ((err = mp_invmod(&q, &p, &key->qP)) != MP_OKAY) { goto error2; } /* qP = 1/q mod p */
if ((err = mp_copy(&p, &key->p)) != MP_OKAY) { goto error2; }
if ((err = mp_copy(&q, &key->q)) != MP_OKAY) { goto error2; }
/* shrink ram required */
if ((err = mp_shrink(&key->e)) != MP_OKAY) { goto error2; }
if ((err = mp_shrink(&key->d)) != MP_OKAY) { goto error2; }
if ((err = mp_shrink(&key->N)) != MP_OKAY) { goto error2; }
if ((err = mp_shrink(&key->dQ)) != MP_OKAY) { goto error2; }
if ((err = mp_shrink(&key->dP)) != MP_OKAY) { goto error2; }
if ((err = mp_shrink(&key->qP)) != MP_OKAY) { goto error2; }
if ((err = mp_shrink(&key->p)) != MP_OKAY) { goto error2; }
if ((err = mp_shrink(&key->q)) != MP_OKAY) { goto error2; }
/* set key type (in this case it's CRT optimized) */
key->type = PK_PRIVATE;
/* return ok and free temps */
err = CRYPT_OK;
goto done;
error2:
mp_clear_multi(&key->d, &key->e, &key->N, &key->dQ, &key->dP,
&key->qP, &key->p, &key->q, NULL);
error:
err = mpi_to_ltc_error(err);
done:
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: 1.3 $ */
/* $Date: 2005/05/05 14:35:59 $ */
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