55
if ((err = mp_init_multi(&tmp, &tmp2, &key->g, &key->q, &key->p, &key->x, &key->y, NULL)) != MP_OKAY) {
56
err = mpi_to_ltc_error(err);
56
if ((err = mp_init_multi(&tmp, &tmp2, &key->g, &key->q, &key->p, &key->x, &key->y, NULL)) != CRYPT_OK) {
60
61
/* make our prime q */
61
if ((err = rand_prime(&key->q, group_size*8, prng, wprng)) != CRYPT_OK) { goto LBL_ERR; }
62
if ((err = rand_prime(key->q, group_size, prng, wprng)) != CRYPT_OK) { goto error; }
64
if ((err = mp_mul_2(&key->q, &tmp)) != MP_OKAY) { goto error; }
65
if ((err = mp_add(key->q, key->q, tmp)) != CRYPT_OK) { goto error; }
66
67
/* now make a random string and multply it against q */
67
68
if (prng_descriptor[wprng].read(buf+1, modulus_size - group_size, prng) != (unsigned long)(modulus_size - group_size)) {
68
69
err = CRYPT_ERROR_READPRNG;
72
73
/* force magnitude */
76
77
buf[modulus_size - group_size - 1] &= ~1;
78
if ((err = mp_read_unsigned_bin(&tmp2, buf, modulus_size - group_size)) != MP_OKAY) { goto error; }
79
if ((err = mp_mul(&key->q, &tmp2, &key->p)) != MP_OKAY) { goto error; }
80
if ((err = mp_add_d(&key->p, 1, &key->p)) != MP_OKAY) { goto error; }
79
if ((err = mp_read_unsigned_bin(tmp2, buf, modulus_size - group_size)) != CRYPT_OK) { goto error; }
80
if ((err = mp_mul(key->q, tmp2, key->p)) != CRYPT_OK) { goto error; }
81
if ((err = mp_add_d(key->p, 1, key->p)) != CRYPT_OK) { goto error; }
82
83
/* now loop until p is prime */
84
if ((err = is_prime(&key->p, &res)) != CRYPT_OK) { goto LBL_ERR; }
85
if (res == MP_YES) break;
85
if ((err = mp_prime_is_prime(key->p, 8, &res)) != CRYPT_OK) { goto error; }
86
if (res == LTC_MP_YES) break;
87
88
/* add 2q to p and 2 to tmp2 */
88
if ((err = mp_add(&tmp, &key->p, &key->p)) != MP_OKAY) { goto error; }
89
if ((err = mp_add_d(&tmp2, 2, &tmp2)) != MP_OKAY) { goto error; }
89
if ((err = mp_add(tmp, key->p, key->p)) != CRYPT_OK) { goto error; }
90
if ((err = mp_add_d(tmp2, 2, tmp2)) != CRYPT_OK) { goto error; }
92
93
/* now p = (q * tmp2) + 1 is prime, find a value g for which g^tmp2 != 1 */
96
if ((err = mp_add_d(&key->g, 1, &key->g)) != MP_OKAY) { goto error; }
97
if ((err = mp_exptmod(&key->g, &tmp2, &key->p, &tmp)) != MP_OKAY) { goto error; }
98
} while (mp_cmp_d(&tmp, 1) == MP_EQ);
97
if ((err = mp_add_d(key->g, 1, key->g)) != CRYPT_OK) { goto error; }
98
if ((err = mp_exptmod(key->g, tmp2, key->p, tmp)) != CRYPT_OK) { goto error; }
99
} while (mp_cmp_d(tmp, 1) == LTC_MP_EQ);
100
101
/* at this point tmp generates a group of order q mod p */
101
mp_exch(&tmp, &key->g);
102
mp_exch(tmp, key->g);
103
104
/* so now we have our DH structure, generator g, order q, modulus p
104
105
Now we need a random exponent [mod q] and it's power g^x mod p
107
108
if (prng_descriptor[wprng].read(buf, group_size, prng) != (unsigned long)group_size) {
108
109
err = CRYPT_ERROR_READPRNG;
111
if ((err = mp_read_unsigned_bin(&key->x, buf, group_size)) != MP_OKAY) { goto error; }
112
} while (mp_cmp_d(&key->x, 1) != MP_GT);
113
if ((err = mp_exptmod(&key->g, &key->x, &key->p, &key->y)) != MP_OKAY) { goto error; }
112
if ((err = mp_read_unsigned_bin(key->x, buf, group_size)) != CRYPT_OK) { goto error; }
113
} while (mp_cmp_d(key->x, 1) != LTC_MP_GT);
114
if ((err = mp_exptmod(key->g, key->x, key->p, key->y)) != CRYPT_OK) { goto error; }
115
116
key->type = PK_PRIVATE;
116
117
key->qord = group_size;
118
/* shrink the ram required */
119
if ((err = mp_shrink(&key->g)) != MP_OKAY) { goto error; }
120
if ((err = mp_shrink(&key->p)) != MP_OKAY) { goto error; }
121
if ((err = mp_shrink(&key->q)) != MP_OKAY) { goto error; }
122
if ((err = mp_shrink(&key->x)) != MP_OKAY) { goto error; }
123
if ((err = mp_shrink(&key->y)) != MP_OKAY) { goto error; }
125
119
#ifdef LTC_CLEAN_STACK
126
120
zeromem(buf, MDSA_DELTA);
132
err = mpi_to_ltc_error(err);
134
mp_clear_multi(&key->g, &key->q, &key->p, &key->x, &key->y, NULL);
126
mp_clear_multi(key->g, key->q, key->p, key->x, key->y, NULL);
136
mp_clear_multi(&tmp, &tmp2, NULL);
128
mp_clear_multi(tmp, tmp2, NULL);