3 This file is part of the AVR-Crypto-Lib.
4 Copyright (C) 2010 Daniel Otte (daniel.otte@rub.de)
6 This program is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
23 #include "hfal-basic.h"
25 uint8_t dsa_verify_bigint(const dsa_signature_t* s, const bigint_t* m,
26 const dsa_ctx_t* ctx){
27 if(s->r.length_B==0 || s->s.length_B==0){
28 return DSA_SIGNATURE_FAIL;
30 if(bigint_cmp_u(&(s->r), &(ctx->domain.q))>=0 || bigint_cmp_u(&(s->s), &(ctx->domain.q))>=0){
31 return DSA_SIGNATURE_FAIL;
33 bigint_t w, u1, u2, v1, v2;
34 uint8_t w_b[ctx->domain.q.length_B], u1_b[ctx->domain.q.length_B*2], u2_b[ctx->domain.q.length_B*2];
35 uint8_t v1_b[ctx->domain.p.length_B*2], v2_b[ctx->domain.p.length_B];
41 bigint_inverse(&w, &(s->s), &(ctx->domain.q));
42 bigint_mul_u(&u1, &w, m);
43 bigint_reduce(&u1, &(ctx->domain.q));
44 bigint_mul_u(&u2, &w, &(s->r));
45 bigint_reduce(&u2, &(ctx->domain.q));
46 bigint_expmod_u(&v1, &(ctx->domain.g), &u1, &(ctx->domain.p));
47 bigint_expmod_u(&v2, &(ctx->pub), &u2, &(ctx->domain.p));
48 bigint_mul_u(&v1, &v1, &v2);
49 bigint_reduce(&v1, &(ctx->domain.p));
50 bigint_reduce(&v1, &(ctx->domain.q));
51 if(bigint_cmp_u(&v1, &(s->r))==0){
52 return DSA_SIGNATURE_OK;
54 return DSA_SIGNATURE_FAIL;
57 uint8_t dsa_verify_message(const dsa_signature_t* s, const void* m, uint16_t m_len_b,
58 const hfdesc_t* hash_desc, const dsa_ctx_t* ctx){
60 uint8_t n_B = ctx->domain.q.length_B;
61 uint8_t hash_value[(hfal_hash_getHashsize(hash_desc)+7)/8];
62 hfal_hash_mem(hash_desc, hash_value, m, m_len_b);
65 bigint_changeendianess(&z);
67 return dsa_verify_bigint(s, &z, ctx);