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
13 RSA 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 e The "e" value (public key). e==65537 is a good choice
24 @param key [out] Destination of a newly created private key pair
25 @return CRYPT_OK if successful, upon error all allocated ram is freed
27 int rsa_make_key(prng_state *prng, int wprng, int size, long e, rsa_key *key)
29 void *p, *q, *tmp1, *tmp2, *tmp3;
32 LTC_ARGCHK(ltc_mp.name != NULL);
33 LTC_ARGCHK(key != NULL);
36 if ((e < 3) || ((e & 1) == 0)) {
37 return CRYPT_INVALID_ARG;
40 if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
44 if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, &tmp3, NULL)) != CRYPT_OK) {
48 /* make primes p and q (optimization provided by Wayne Scott) */
49 if ((err = mp_set_int(tmp3, e)) != CRYPT_OK) { goto cleanup; } /* tmp3 = e */
53 if ((err = rand_prime( p, size/2, prng, wprng)) != CRYPT_OK) { goto cleanup; }
54 if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto cleanup; } /* tmp1 = p-1 */
55 if ((err = mp_gcd( tmp1, tmp3, tmp2)) != CRYPT_OK) { goto cleanup; } /* tmp2 = gcd(p-1, e) */
56 } while (mp_cmp_d( tmp2, 1) != 0); /* while e divides p-1 */
60 if ((err = rand_prime( q, size/2, prng, wprng)) != CRYPT_OK) { goto cleanup; }
61 if ((err = mp_sub_d( q, 1, tmp1)) != CRYPT_OK) { goto cleanup; } /* tmp1 = q-1 */
62 if ((err = mp_gcd( tmp1, tmp3, tmp2)) != CRYPT_OK) { goto cleanup; } /* tmp2 = gcd(q-1, e) */
63 } while (mp_cmp_d( tmp2, 1) != 0); /* while e divides q-1 */
65 /* tmp1 = lcm(p-1, q-1) */
66 if ((err = mp_sub_d( p, 1, tmp2)) != CRYPT_OK) { goto cleanup; } /* tmp2 = p-1 */
67 /* tmp1 = q-1 (previous do/while loop) */
68 if ((err = mp_lcm( tmp1, tmp2, tmp1)) != CRYPT_OK) { goto cleanup; } /* tmp1 = lcm(p-1, q-1) */
71 if ((err = mp_init_multi(&key->e, &key->d, &key->N, &key->dQ, &key->dP, &key->qP, &key->p, &key->q, NULL)) != CRYPT_OK) {
75 if ((err = mp_set_int( key->e, e)) != CRYPT_OK) { goto errkey; } /* key->e = e */
76 if ((err = mp_invmod( key->e, tmp1, key->d)) != CRYPT_OK) { goto errkey; } /* key->d = 1/e mod lcm(p-1,q-1) */
77 if ((err = mp_mul( p, q, key->N)) != CRYPT_OK) { goto errkey; } /* key->N = pq */
79 /* optimize for CRT now */
80 /* find d mod q-1 and d mod p-1 */
81 if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto errkey; } /* tmp1 = q-1 */
82 if ((err = mp_sub_d( q, 1, tmp2)) != CRYPT_OK) { goto errkey; } /* tmp2 = p-1 */
83 if ((err = mp_mod( key->d, tmp1, key->dP)) != CRYPT_OK) { goto errkey; } /* dP = d mod p-1 */
84 if ((err = mp_mod( key->d, tmp2, key->dQ)) != CRYPT_OK) { goto errkey; } /* dQ = d mod q-1 */
85 if ((err = mp_invmod( q, p, key->qP)) != CRYPT_OK) { goto errkey; } /* qP = 1/q mod p */
87 if ((err = mp_copy( p, key->p)) != CRYPT_OK) { goto errkey; }
88 if ((err = mp_copy( q, key->q)) != CRYPT_OK) { goto errkey; }
90 /* set key type (in this case it's CRT optimized) */
91 key->type = PK_PRIVATE;
93 /* return ok and free temps */
99 mp_clear_multi(tmp3, tmp2, tmp1, q, p, NULL);
105 /* ref: $Format:%D$ */
106 /* git commit: $Format:%H$ */
107 /* commit time: $Format:%ai$ */