/************************************************* * EME1 Source File * * (C) 1999-2007 Jack Lloyd * *************************************************/ #include #include #include #include #include namespace Botan { /************************************************* * EME1 Pad Operation * *************************************************/ SecureVector EME1::pad(const byte in[], u32bit in_length, u32bit key_length) const { key_length /= 8; if(in_length > key_length - 2*HASH_LENGTH - 1) throw Exception("EME1: Input is too large"); SecureVector out(key_length); out.clear(); Global_RNG::randomize(out, HASH_LENGTH); out.copy(HASH_LENGTH, Phash, Phash.size()); out[out.size() - in_length - 1] = 0x01; out.copy(out.size() - in_length, in, in_length); mgf->mask(out, HASH_LENGTH, out + HASH_LENGTH, out.size() - HASH_LENGTH); mgf->mask(out + HASH_LENGTH, out.size() - HASH_LENGTH, out, HASH_LENGTH); return out; } /************************************************* * EME1 Unpad Operation * *************************************************/ SecureVector EME1::unpad(const byte in[], u32bit in_length, u32bit key_length) const { key_length /= 8; if(in_length > key_length) throw Decoding_Error("Invalid EME1 encoding"); SecureVector tmp(key_length); tmp.copy(key_length - in_length, in, in_length); mgf->mask(tmp + HASH_LENGTH, tmp.size() - HASH_LENGTH, tmp, HASH_LENGTH); mgf->mask(tmp, HASH_LENGTH, tmp + HASH_LENGTH, tmp.size() - HASH_LENGTH); for(u32bit j = 0; j != Phash.size(); ++j) if(tmp[j+HASH_LENGTH] != Phash[j]) throw Decoding_Error("Invalid EME1 encoding"); for(u32bit j = HASH_LENGTH + Phash.size(); j != tmp.size(); ++j) { if(tmp[j] && tmp[j] != 0x01) throw Decoding_Error("Invalid EME1 encoding"); if(tmp[j] && tmp[j] == 0x01) { SecureVector retval(tmp + j + 1, tmp.size() - j - 1); return retval; } } throw Decoding_Error("Invalid EME1 encoding"); } /************************************************* * Return the max input size for a given key size * *************************************************/ u32bit EME1::maximum_input_size(u32bit keybits) const { if(keybits / 8 > 2*HASH_LENGTH + 1) return ((keybits / 8) - 2*HASH_LENGTH - 1); else return 0; } /************************************************* * EME1 Constructor * *************************************************/ EME1::EME1(const std::string& hash_name, const std::string& mgf_name, const std::string& P) : HASH_LENGTH(output_length_of(hash_name)) { mgf = get_mgf(mgf_name + "(" + hash_name + ")"); std::auto_ptr hash(get_hash(hash_name)); Phash = hash->process(P); } }