1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
6 * The library is free for all purposes without any express
12 @file katja_make_key.c
13 Katja key generation, Tom St Denis
20 @param prng An active PRNG state
21 @param wprng The index of the PRNG desired
22 @param size The size of the modulus (key size) desired (octets)
23 @param key [out] Destination of a newly created private key pair
24 @return CRYPT_OK if successful, upon error all allocated ram is freed
26 int katja_make_key(prng_state *prng, int wprng, int size, katja_key *key)
28 void *p, *q, *tmp1, *tmp2;
31 LTC_ARGCHK(key != NULL);
32 LTC_ARGCHK(ltc_mp.name != NULL);
34 if ((size < (MIN_KAT_SIZE/8)) || (size > (MAX_KAT_SIZE/8))) {
35 return CRYPT_INVALID_KEYSIZE;
38 if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
42 if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, NULL)) != CRYPT_OK) {
46 /* divide size by three */
47 size = (((size << 3) / 3) + 7) >> 3;
49 /* make prime "q" (we negate size to make q == 3 mod 4) */
50 if ((err = rand_prime(q, -size, prng, wprng)) != CRYPT_OK) { goto done; }
51 if ((err = mp_sub_d(q, 1, tmp1)) != CRYPT_OK) { goto done; }
55 if ((err = rand_prime(p, size+1, prng, wprng)) != CRYPT_OK) { goto done; }
56 if ((err = mp_gcd(p, tmp1, tmp2)) != CRYPT_OK) { goto done; }
57 } while (mp_cmp_d(tmp2, 1) != LTC_MP_EQ);
60 if ((err = mp_init_multi(&key->d, &key->N, &key->dQ, &key->dP,
61 &key->qP, &key->p, &key->q, &key->pq, NULL)) != CRYPT_OK) {
65 /* n=p^2q and 1/n mod pq */
66 if ((err = mp_copy( p, key->p)) != CRYPT_OK) { goto error2; }
67 if ((err = mp_copy( q, key->q)) != CRYPT_OK) { goto error2; }
68 if ((err = mp_mul(key->p, key->q, key->pq)) != CRYPT_OK) { goto error2; } /* tmp1 = pq */
69 if ((err = mp_mul(key->pq, key->p, key->N)) != CRYPT_OK) { goto error2; } /* N = p^2q */
70 if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto error2; } /* tmp1 = q-1 */
71 if ((err = mp_sub_d( q, 1, tmp2)) != CRYPT_OK) { goto error2; } /* tmp2 = p-1 */
72 if ((err = mp_lcm(tmp1, tmp2, key->d)) != CRYPT_OK) { goto error2; } /* tmp1 = lcd(p-1,q-1) */
73 if ((err = mp_invmod( key->N, key->d, key->d)) != CRYPT_OK) { goto error2; } /* key->d = 1/N mod pq */
75 /* optimize for CRT now */
76 /* find d mod q-1 and d mod p-1 */
77 if ((err = mp_mod( key->d, tmp1, key->dP)) != CRYPT_OK) { goto error2; } /* dP = d mod p-1 */
78 if ((err = mp_mod( key->d, tmp2, key->dQ)) != CRYPT_OK) { goto error2; } /* dQ = d mod q-1 */
79 if ((err = mp_invmod( q, p, key->qP)) != CRYPT_OK) { goto error2; } /* qP = 1/q mod p */
81 /* set key type (in this case it's CRT optimized) */
82 key->type = PK_PRIVATE;
84 /* return ok and free temps */
88 mp_clear_multi( key->d, key->N, key->dQ, key->dP, key->qP, key->p, key->q, key->pq, NULL);
91 mp_clear_multi( tmp2, tmp1, p, q, NULL);
97 /* ref: $Format:%D$ */
98 /* git commit: $Format:%H$ */
99 /* commit time: $Format:%ai$ */