Mercurial > dropbear
comparison src/pk/dsa/dsa_verify_key.c @ 280:59400faa4b44 libtomcrypt-orig libtomcrypt-1.05
Re-import libtomcrypt 1.05 for cleaner propagating.
From crypt-1.05.tar.bz2, SHA1 of 88250202bb51570dc64f7e8f1c943cda9479258f
author | Matt Johnston <matt@ucc.asn.au> |
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date | Wed, 08 Mar 2006 12:58:00 +0000 |
parents | |
children | d5faf4814ddb |
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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 "tomcrypt.h" | |
12 | |
13 /** | |
14 @file dsa_verify_key.c | |
15 DSA implementation, verify a key, Tom St Denis | |
16 */ | |
17 | |
18 #ifdef MDSA | |
19 | |
20 /** | |
21 Verify a DSA key for validity | |
22 @param key The key to verify | |
23 @param stat [out] Result of test, 1==valid, 0==invalid | |
24 @return CRYPT_OK if successful | |
25 */ | |
26 int dsa_verify_key(dsa_key *key, int *stat) | |
27 { | |
28 mp_int tmp, tmp2; | |
29 int res, err; | |
30 | |
31 LTC_ARGCHK(key != NULL); | |
32 LTC_ARGCHK(stat != NULL); | |
33 | |
34 /* default to an invalid key */ | |
35 *stat = 0; | |
36 | |
37 /* first make sure key->q and key->p are prime */ | |
38 if ((err = is_prime(&key->q, &res)) != CRYPT_OK) { | |
39 return err; | |
40 } | |
41 if (res == 0) { | |
42 return CRYPT_OK; | |
43 } | |
44 | |
45 | |
46 if ((err = is_prime(&key->p, &res)) != CRYPT_OK) { | |
47 return err; | |
48 } | |
49 if (res == 0) { | |
50 return CRYPT_OK; | |
51 } | |
52 | |
53 /* now make sure that g is not -1, 0 or 1 and <p */ | |
54 if (mp_cmp_d(&key->g, 0) == MP_EQ || mp_cmp_d(&key->g, 1) == MP_EQ) { | |
55 return CRYPT_OK; | |
56 } | |
57 if ((err = mp_init_multi(&tmp, &tmp2, NULL)) != MP_OKAY) { goto error; } | |
58 if ((err = mp_sub_d(&key->p, 1, &tmp)) != MP_OKAY) { goto error; } | |
59 if (mp_cmp(&tmp, &key->g) == MP_EQ || mp_cmp(&key->g, &key->p) != MP_LT) { | |
60 err = CRYPT_OK; | |
61 goto done; | |
62 } | |
63 | |
64 /* 1 < y < p-1 */ | |
65 if (!(mp_cmp_d(&key->y, 1) == MP_GT && mp_cmp(&key->y, &tmp) == MP_LT)) { | |
66 err = CRYPT_OK; | |
67 goto done; | |
68 } | |
69 | |
70 /* now we have to make sure that g^q = 1, and that p-1/q gives 0 remainder */ | |
71 if ((err = mp_div(&tmp, &key->q, &tmp, &tmp2)) != MP_OKAY) { goto error; } | |
72 if (mp_iszero(&tmp2) != MP_YES) { | |
73 err = CRYPT_OK; | |
74 goto done; | |
75 } | |
76 | |
77 if ((err = mp_exptmod(&key->g, &key->q, &key->p, &tmp)) != MP_OKAY) { goto error; } | |
78 if (mp_cmp_d(&tmp, 1) != MP_EQ) { | |
79 err = CRYPT_OK; | |
80 goto done; | |
81 } | |
82 | |
83 /* now we have to make sure that y^q = 1, this makes sure y \in g^x mod p */ | |
84 if ((err = mp_exptmod(&key->y, &key->q, &key->p, &tmp)) != MP_OKAY) { goto error; } | |
85 if (mp_cmp_d(&tmp, 1) != MP_EQ) { | |
86 err = CRYPT_OK; | |
87 goto done; | |
88 } | |
89 | |
90 /* at this point we are out of tests ;-( */ | |
91 err = CRYPT_OK; | |
92 *stat = 1; | |
93 goto done; | |
94 error: err = mpi_to_ltc_error(err); | |
95 done : mp_clear_multi(&tmp, &tmp2, NULL); | |
96 return err; | |
97 } | |
98 #endif | |
99 | |
100 /* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_verify_key.c,v $ */ | |
101 /* $Revision: 1.3 $ */ | |
102 /* $Date: 2005/05/05 14:35:59 $ */ |