/* * EMSA2 * (C) 1999-2007 Jack Lloyd * * Distributed under the terms of the Botan license */ #include #include namespace Botan { namespace { /* * EMSA2 Encode Operation */ SecureVector emsa2_encoding(const MemoryRegion& msg, u32bit output_bits, const MemoryRegion& empty_hash, byte hash_id) { const u32bit HASH_SIZE = empty_hash.size(); u32bit output_length = (output_bits + 1) / 8; if(msg.size() != HASH_SIZE) throw Encoding_Error("EMSA2::encoding_of: Bad input length"); if(output_length < HASH_SIZE + 4) throw Encoding_Error("EMSA2::encoding_of: Output length is too small"); bool empty = true; for(u32bit j = 0; j != HASH_SIZE; ++j) if(empty_hash[j] != msg[j]) empty = false; SecureVector output(output_length); output[0] = (empty ? 0x4B : 0x6B); output[output_length - 3 - HASH_SIZE] = 0xBA; set_mem(output + 1, output_length - 4 - HASH_SIZE, 0xBB); output.copy(output_length - (HASH_SIZE + 2), msg, msg.size()); output[output_length-2] = hash_id; output[output_length-1] = 0xCC; return output; } } /* * EMSA2 Update Operation */ void EMSA2::update(const byte input[], u32bit length) { hash->update(input, length); } /* * Return the raw (unencoded) data */ SecureVector EMSA2::raw_data() { return hash->final(); } /* * EMSA2 Encode Operation */ SecureVector EMSA2::encoding_of(const MemoryRegion& msg, u32bit output_bits, RandomNumberGenerator&) { return emsa2_encoding(msg, output_bits, empty_hash, hash_id); } /* * EMSA2 Verify Operation */ bool EMSA2::verify(const MemoryRegion& coded, const MemoryRegion& raw, u32bit key_bits) throw() { try { return (coded == emsa2_encoding(raw, key_bits, empty_hash, hash_id)); } catch(...) { return false; } } /* * EMSA2 Constructor */ EMSA2::EMSA2(HashFunction* hash_in) : hash(hash_in) { empty_hash = hash->final(); hash_id = ieee1363_hash_id(hash->name()); if(hash_id == 0) { delete hash; throw Encoding_Error("EMSA2 cannot be used with " + hash->name()); } } }