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
9
* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org
15
RSA key generation, Tom St Denis
22
@param prng An active PRNG state
23
@param wprng The index of the PRNG desired
24
@param size The size of the modulus (key size) desired (octets)
25
@param e The "e" value (public key). e==65537 is a good choice
26
@param key [out] Destination of a newly created private key pair
27
@return CRYPT_OK if successful, upon error all allocated ram is freed
29
int rsa_make_key(prng_state *prng, int wprng, int size, long e, rsa_key *key)
31
mp_int p, q, tmp1, tmp2, tmp3;
34
LTC_ARGCHK(key != NULL);
36
if ((size < (MIN_RSA_SIZE/8)) || (size > (MAX_RSA_SIZE/8))) {
37
return CRYPT_INVALID_KEYSIZE;
40
if ((e < 3) || ((e & 1) == 0)) {
41
return CRYPT_INVALID_ARG;
44
if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
48
if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, &tmp3, NULL)) != MP_OKAY) {
49
return mpi_to_ltc_error(err);
52
/* make primes p and q (optimization provided by Wayne Scott) */
53
if ((err = mp_set_int(&tmp3, e)) != MP_OKAY) { goto error; } /* tmp3 = e */
57
if ((err = rand_prime(&p, size*4, prng, wprng)) != CRYPT_OK) { goto done; }
58
if ((err = mp_sub_d(&p, 1, &tmp1)) != MP_OKAY) { goto error; } /* tmp1 = p-1 */
59
if ((err = mp_gcd(&tmp1, &tmp3, &tmp2)) != MP_OKAY) { goto error; } /* tmp2 = gcd(p-1, e) */
60
} while (mp_cmp_d(&tmp2, 1) != 0); /* while e divides p-1 */
64
if ((err = rand_prime(&q, size*4, prng, wprng)) != CRYPT_OK) { goto done; }
65
if ((err = mp_sub_d(&q, 1, &tmp1)) != MP_OKAY) { goto error; } /* tmp1 = q-1 */
66
if ((err = mp_gcd(&tmp1, &tmp3, &tmp2)) != MP_OKAY) { goto error; } /* tmp2 = gcd(q-1, e) */
67
} while (mp_cmp_d(&tmp2, 1) != 0); /* while e divides q-1 */
69
/* tmp1 = lcm(p-1, q-1) */
70
if ((err = mp_sub_d(&p, 1, &tmp2)) != MP_OKAY) { goto error; } /* tmp2 = p-1 */
71
/* tmp1 = q-1 (previous do/while loop) */
72
if ((err = mp_lcm(&tmp1, &tmp2, &tmp1)) != MP_OKAY) { goto error; } /* tmp1 = lcm(p-1, q-1) */
75
if ((err = mp_init_multi(&key->e, &key->d, &key->N, &key->dQ, &key->dP,
76
&key->qP, &key->p, &key->q, NULL)) != MP_OKAY) {
80
if ((err = mp_set_int(&key->e, e)) != MP_OKAY) { goto error2; } /* key->e = e */
81
if ((err = mp_invmod(&key->e, &tmp1, &key->d)) != MP_OKAY) { goto error2; } /* key->d = 1/e mod lcm(p-1,q-1) */
82
if ((err = mp_mul(&p, &q, &key->N)) != MP_OKAY) { goto error2; } /* key->N = pq */
84
/* optimize for CRT now */
85
/* find d mod q-1 and d mod p-1 */
86
if ((err = mp_sub_d(&p, 1, &tmp1)) != MP_OKAY) { goto error2; } /* tmp1 = q-1 */
87
if ((err = mp_sub_d(&q, 1, &tmp2)) != MP_OKAY) { goto error2; } /* tmp2 = p-1 */
88
if ((err = mp_mod(&key->d, &tmp1, &key->dP)) != MP_OKAY) { goto error2; } /* dP = d mod p-1 */
89
if ((err = mp_mod(&key->d, &tmp2, &key->dQ)) != MP_OKAY) { goto error2; } /* dQ = d mod q-1 */
90
if ((err = mp_invmod(&q, &p, &key->qP)) != MP_OKAY) { goto error2; } /* qP = 1/q mod p */
92
if ((err = mp_copy(&p, &key->p)) != MP_OKAY) { goto error2; }
93
if ((err = mp_copy(&q, &key->q)) != MP_OKAY) { goto error2; }
95
/* shrink ram required */
96
if ((err = mp_shrink(&key->e)) != MP_OKAY) { goto error2; }
97
if ((err = mp_shrink(&key->d)) != MP_OKAY) { goto error2; }
98
if ((err = mp_shrink(&key->N)) != MP_OKAY) { goto error2; }
99
if ((err = mp_shrink(&key->dQ)) != MP_OKAY) { goto error2; }
100
if ((err = mp_shrink(&key->dP)) != MP_OKAY) { goto error2; }
101
if ((err = mp_shrink(&key->qP)) != MP_OKAY) { goto error2; }
102
if ((err = mp_shrink(&key->p)) != MP_OKAY) { goto error2; }
103
if ((err = mp_shrink(&key->q)) != MP_OKAY) { goto error2; }
105
/* set key type (in this case it's CRT optimized) */
106
key->type = PK_PRIVATE;
108
/* return ok and free temps */
112
mp_clear_multi(&key->d, &key->e, &key->N, &key->dQ, &key->dP,
113
&key->qP, &key->p, &key->q, NULL);
115
err = mpi_to_ltc_error(err);
117
mp_clear_multi(&tmp3, &tmp2, &tmp1, &p, &q, NULL);
123
/* $Source: /cvs/libtom/libtomcrypt/src/pk/rsa/rsa_make_key.c,v $ */
124
/* $Revision: 1.3 $ */
125
/* $Date: 2005/05/05 14:35:59 $ */