1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis */
2 /* SPDX-License-Identifier: Unlicense */
3 #include "tomcrypt_private.h"
4
5 /**
6 @file dsa_make_key.c
7 DSA implementation, generate a DSA key
8 */
9
10 #ifdef LTC_MDSA
11
12 /**
13 Create a DSA key
14 @param prng An active PRNG state
15 @param wprng The index of the PRNG desired
16 @param key [in/out] Where to store the created key
17 @return CRYPT_OK if successful.
18 */
dsa_generate_key(prng_state * prng,int wprng,dsa_key * key)19 int dsa_generate_key(prng_state *prng, int wprng, dsa_key *key)
20 {
21 int err;
22
23 LTC_ARGCHK(key != NULL);
24 LTC_ARGCHK(ltc_mp.name != NULL);
25
26 /* so now we have our DH structure, generator g, order q, modulus p
27 Now we need a random exponent [mod q] and it's power g^x mod p
28 */
29 /* private key x should be from range: 1 <= x <= q-1 (see FIPS 186-4 B.1.2) */
30 if ((err = rand_bn_upto(key->x, key->q, prng, wprng)) != CRYPT_OK) { return err; }
31 if ((err = mp_exptmod(key->g, key->x, key->p, key->y)) != CRYPT_OK) { return err; }
32 key->type = PK_PRIVATE;
33
34 return CRYPT_OK;
35 }
36
37 #endif
38