/**
* From the Lucky13 paper: An individual record R (viewed as a byte sequence of length at least
* zero) is processed as follows. The sender maintains an 8-byte sequence number SQN which is
* incremented for each record sent, and forms a 5-byte field HDR consisting of a 1-byte type
* field, a 2-byte version field, and a 2-byte length field. It then calculates a MAC over the
* bytes SQN || HDR || R.
*
* @param protocolVersion
* @param contentType
* @param data
* @return
*/
public byte[] calculateMac(
ProtocolVersion protocolVersion, ProtocolMessageType contentType, byte[] data) {
byte[] SQN = ArrayConverter.longToUint64Bytes(sequenceNumber);
byte[] HDR =
ArrayConverter.concatenate(
contentType.getArrayValue(),
protocolVersion.getValue(),
ArrayConverter.intToBytes(data.length, 2));
writeMac.update(SQN);
writeMac.update(HDR);
writeMac.update(data);
LOGGER.debug(
"The MAC was caluculated over the following data: {}",
ArrayConverter.bytesToHexString(ArrayConverter.concatenate(SQN, HDR, data)));
byte[] result = writeMac.doFinal();
LOGGER.debug("MAC result: {}", ArrayConverter.bytesToHexString(result));
// we increment sequence number for the sent records
sequenceNumber++;
return result;
}
