Introducing Robustness into Message Authentication

Message Authentication Codes are very sensitive to any change of the message they are appended to. If one or more bits of the message change, Message Authentication Codes change about 50\\ % of their bits, making the message useless. The successful verification of Message Authentication Codes demands equality of all of bits of the received Message Authentication Code and that one recalculated of the received message. Such a hard condition for the successful verification of messages protected by Message Authentication Codes is not suitable for some applications. The introduction of a softer condition for the successful verification can enable the correction and improve the successful of messages corrupted by transmission over a noisy channel. An algorithm is presented, which introduces robustness into the verification of messages protected by Message Authentication Codes together with a correction of messages corrupted due to the noisy channel. Results show how promising the algorithm is for correction of messages, which have an error rate despite of the use of channel codes. Key words: Message Authentication Codes; robustness; soft decision; reliability values; Hamming distance.