| 166 | |
| 167 | |
| 168 | word32 DSA_Signer::Sign(const byte* sha_digest, byte* sig, |
| 169 | RandomNumberGenerator& rng) |
| 170 | { |
| 171 | const Integer& p = key_.GetModulus(); |
| 172 | const Integer& q = key_.GetSubGroupOrder(); |
| 173 | const Integer& g = key_.GetSubGroupGenerator(); |
| 174 | const Integer& x = key_.GetPrivatePart(); |
| 175 | |
| 176 | Integer k(rng, 1, q - 1); |
| 177 | |
| 178 | r_ = a_exp_b_mod_c(g, k, p); |
| 179 | r_ %= q; |
| 180 | |
| 181 | Integer H(sha_digest, SHA::DIGEST_SIZE); // sha Hash(m) |
| 182 | |
| 183 | Integer kInv = k.InverseMod(q); |
| 184 | s_ = (kInv * (H + x*r_)) % q; |
| 185 | |
| 186 | if (!(!!r_ && !!s_)) |
| 187 | return -1; |
| 188 | |
| 189 | int rSz = r_.ByteCount(); |
| 190 | |
| 191 | if (rSz == 19) { |
| 192 | sig[0] = 0; |
| 193 | sig++; |
| 194 | } |
| 195 | |
| 196 | r_.Encode(sig, rSz); |
| 197 | |
| 198 | int sSz = s_.ByteCount(); |
| 199 | |
| 200 | if (sSz == 19) { |
| 201 | sig[rSz] = 0; |
| 202 | sig++; |
| 203 | } |
| 204 | |
| 205 | s_.Encode(sig + rSz, sSz); |
| 206 | |
| 207 | return 40; |
| 208 | } |
| 209 | |
| 210 | |
| 211 | DSA_Verifier::DSA_Verifier(const DSA_PublicKey& key) |