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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 katja_make_key.c
Katja key generation, Tom St Denis
*/
#ifdef MKAT
/**
Create a Katja 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 key [out] Destination of a newly created private key pair
@return CRYPT_OK if successful, upon error all allocated ram is freed
*/
int katja_make_key(prng_state *prng, int wprng, int size, katja_key *key)
{
void *p, *q, *tmp1, *tmp2;
int err;
LTC_ARGCHK(key != NULL);
LTC_ARGCHK(ltc_mp.name != NULL);
if ((size < (MIN_KAT_SIZE/8)) || (size > (MAX_KAT_SIZE/8))) {
return CRYPT_INVALID_KEYSIZE;
}
if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
return err;
}
if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, NULL)) != CRYPT_OK) {
return err;
}
/* divide size by three */
size = (((size << 3) / 3) + 7) >> 3;
/* make prime "q" (we negate size to make q == 3 mod 4) */
if ((err = rand_prime(q, -size, prng, wprng)) != CRYPT_OK) { goto done; }
if ((err = mp_sub_d(q, 1, tmp1)) != CRYPT_OK) { goto done; }
/* make prime "p" */
do {
if ((err = rand_prime(p, size+1, prng, wprng)) != CRYPT_OK) { goto done; }
if ((err = mp_gcd(p, tmp1, tmp2)) != CRYPT_OK) { goto done; }
} while (mp_cmp_d(tmp2, 1) != LTC_MP_EQ);
/* make key */
if ((err = mp_init_multi(&key->d, &key->N, &key->dQ, &key->dP,
&key->qP, &key->p, &key->q, &key->pq, NULL)) != CRYPT_OK) {
goto error;
}
/* n=p^2q and 1/n mod pq */
if ((err = mp_copy( p, key->p)) != CRYPT_OK) { goto error2; }
if ((err = mp_copy( q, key->q)) != CRYPT_OK) { goto error2; }
if ((err = mp_mul(key->p, key->q, key->pq)) != CRYPT_OK) { goto error2; } /* tmp1 = pq */
if ((err = mp_mul(key->pq, key->p, key->N)) != CRYPT_OK) { goto error2; } /* N = p^2q */
if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto error2; } /* tmp1 = q-1 */
if ((err = mp_sub_d( q, 1, tmp2)) != CRYPT_OK) { goto error2; } /* tmp2 = p-1 */
if ((err = mp_lcm(tmp1, tmp2, key->d)) != CRYPT_OK) { goto error2; } /* tmp1 = lcd(p-1,q-1) */
if ((err = mp_invmod( key->N, key->d, key->d)) != CRYPT_OK) { goto error2; } /* key->d = 1/N mod pq */
/* optimize for CRT now */
/* find d mod q-1 and d mod p-1 */
if ((err = mp_mod( key->d, tmp1, key->dP)) != CRYPT_OK) { goto error2; } /* dP = d mod p-1 */
if ((err = mp_mod( key->d, tmp2, key->dQ)) != CRYPT_OK) { goto error2; } /* dQ = d mod q-1 */
if ((err = mp_invmod( q, p, key->qP)) != CRYPT_OK) { goto error2; } /* qP = 1/q mod p */
/* 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->N, key->dQ, key->dP, key->qP, key->p, key->q, key->pq, NULL);
error:
done:
mp_clear_multi( tmp2, tmp1, p, q, NULL);
return err;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/pk/katja/katja_make_key.c,v $ */
/* $Revision: 1.10 $ */
/* $Date: 2006/03/31 14:15:35 $ */
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