|
3
|
1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
|
|
2 * |
|
|
3 * LibTomCrypt is a library that provides various cryptographic |
|
|
4 * algorithms in a highly modular and flexible manner. |
|
|
5 * |
|
|
6 * The library is free for all purposes without any express |
|
|
7 * guarantee it works. |
|
|
8 * |
|
|
9 * Tom St Denis, [email protected], http://libtomcrypt.org |
|
|
10 */ |
|
|
11 #include "mycrypt.h" |
|
|
12 |
|
|
13 #ifdef MDSA |
|
|
14 |
|
|
15 int dsa_make_key(prng_state *prng, int wprng, int group_size, int modulus_size, dsa_key *key) |
|
|
16 { |
|
143
|
17 mp_int tmp, tmp2; |
|
|
18 int err, res; |
|
|
19 unsigned char *buf; |
|
3
|
20 |
|
|
21 _ARGCHK(key != NULL); |
|
|
22 |
|
|
23 /* check prng */ |
|
|
24 if ((err = prng_is_valid(wprng)) != CRYPT_OK) { |
|
|
25 return err; |
|
|
26 } |
|
|
27 |
|
|
28 /* check size */ |
|
143
|
29 if (group_size >= MDSA_MAX_GROUP || group_size <= 15 || |
|
|
30 group_size >= modulus_size || (modulus_size - group_size) >= MDSA_DELTA) { |
|
3
|
31 return CRYPT_INVALID_ARG; |
|
|
32 } |
|
|
33 |
|
143
|
34 /* allocate ram */ |
|
|
35 buf = XMALLOC(MDSA_DELTA); |
|
|
36 if (buf == NULL) { |
|
|
37 return CRYPT_MEM; |
|
|
38 } |
|
|
39 |
|
3
|
40 /* init mp_ints */ |
|
|
41 if ((err = mp_init_multi(&tmp, &tmp2, &key->g, &key->q, &key->p, &key->x, &key->y, NULL)) != MP_OKAY) { |
|
143
|
42 err = mpi_to_ltc_error(err); |
|
|
43 goto __ERR; |
|
3
|
44 } |
|
|
45 |
|
|
46 /* make our prime q */ |
|
143
|
47 if ((err = rand_prime(&key->q, group_size*8, prng, wprng)) != CRYPT_OK) { goto __ERR; } |
|
3
|
48 |
|
|
49 /* double q */ |
|
143
|
50 if ((err = mp_mul_2(&key->q, &tmp)) != MP_OKAY) { goto error; } |
|
3
|
51 |
|
|
52 /* now make a random string and multply it against q */ |
|
|
53 if (prng_descriptor[wprng].read(buf+1, modulus_size - group_size, prng) != (unsigned long)(modulus_size - group_size)) { |
|
|
54 err = CRYPT_ERROR_READPRNG; |
|
143
|
55 goto __ERR; |
|
3
|
56 } |
|
|
57 |
|
|
58 /* force magnitude */ |
|
|
59 buf[0] = 1; |
|
|
60 |
|
|
61 /* force even */ |
|
|
62 buf[modulus_size - group_size] &= ~1; |
|
|
63 |
|
|
64 if ((err = mp_read_unsigned_bin(&tmp2, buf, modulus_size - group_size+1)) != MP_OKAY) { goto error; } |
|
|
65 if ((err = mp_mul(&key->q, &tmp2, &key->p)) != MP_OKAY) { goto error; } |
|
|
66 if ((err = mp_add_d(&key->p, 1, &key->p)) != MP_OKAY) { goto error; } |
|
|
67 |
|
|
68 /* now loop until p is prime */ |
|
|
69 for (;;) { |
|
143
|
70 if ((err = is_prime(&key->p, &res)) != CRYPT_OK) { goto __ERR; } |
|
3
|
71 if (res == MP_YES) break; |
|
|
72 |
|
|
73 /* add 2q to p and 2 to tmp2 */ |
|
|
74 if ((err = mp_add(&tmp, &key->p, &key->p)) != MP_OKAY) { goto error; } |
|
|
75 if ((err = mp_add_d(&tmp2, 2, &tmp2)) != MP_OKAY) { goto error; } |
|
|
76 } |
|
|
77 |
|
|
78 /* now p = (q * tmp2) + 1 is prime, find a value g for which g^tmp2 != 1 */ |
|
|
79 mp_set(&key->g, 1); |
|
|
80 |
|
|
81 do { |
|
|
82 if ((err = mp_add_d(&key->g, 1, &key->g)) != MP_OKAY) { goto error; } |
|
|
83 if ((err = mp_exptmod(&key->g, &tmp2, &key->p, &tmp)) != MP_OKAY) { goto error; } |
|
|
84 } while (mp_cmp_d(&tmp, 1) == MP_EQ); |
|
|
85 |
|
|
86 /* at this point tmp generates a group of order q mod p */ |
|
|
87 mp_exch(&tmp, &key->g); |
|
|
88 |
|
|
89 /* so now we have our DH structure, generator g, order q, modulus p |
|
|
90 Now we need a random exponent [mod q] and it's power g^x mod p |
|
|
91 */ |
|
|
92 do { |
|
|
93 if (prng_descriptor[wprng].read(buf, group_size, prng) != (unsigned long)group_size) { |
|
|
94 err = CRYPT_ERROR_READPRNG; |
|
143
|
95 goto __ERR; |
|
3
|
96 } |
|
|
97 if ((err = mp_read_unsigned_bin(&key->x, buf, group_size)) != MP_OKAY) { goto error; } |
|
|
98 } while (mp_cmp_d(&key->x, 1) != MP_GT); |
|
|
99 if ((err = mp_exptmod(&key->g, &key->x, &key->p, &key->y)) != MP_OKAY) { goto error; } |
|
|
100 |
|
|
101 key->type = PK_PRIVATE; |
|
|
102 key->qord = group_size; |
|
|
103 |
|
|
104 /* shrink the ram required */ |
|
|
105 if ((err = mp_shrink(&key->g)) != MP_OKAY) { goto error; } |
|
|
106 if ((err = mp_shrink(&key->p)) != MP_OKAY) { goto error; } |
|
|
107 if ((err = mp_shrink(&key->q)) != MP_OKAY) { goto error; } |
|
|
108 if ((err = mp_shrink(&key->x)) != MP_OKAY) { goto error; } |
|
|
109 if ((err = mp_shrink(&key->y)) != MP_OKAY) { goto error; } |
|
|
110 |
|
|
111 #ifdef CLEAN_STACK |
|
143
|
112 zeromem(buf, MDSA_DELTA); |
|
3
|
113 #endif |
|
|
114 |
|
143
|
115 err = CRYPT_OK; |
|
3
|
116 goto done; |
|
143
|
117 error: |
|
|
118 err = mpi_to_ltc_error(err); |
|
|
119 __ERR: |
|
|
120 mp_clear_multi(&key->g, &key->q, &key->p, &key->x, &key->y, NULL); |
|
|
121 done: |
|
|
122 mp_clear_multi(&tmp, &tmp2, NULL); |
|
|
123 |
|
|
124 XFREE(buf); |
|
|
125 return err; |
|
3
|
126 } |
|
|
127 |
|
|
128 #endif |
