Trust in corrected messages protected by message authentication codes

Abstract

An algorithm for correction and soft verification of message protected by cryptographic check values like MAC is presented. The algorithm uses soft output values of the channel decoder which are given as input of the cryptographic verification module. The criterion of standard verification becomes less strict, when the algorithm for correction and soft verification is introduced. Soft verification allows the correction of messages, if only some bits of the message and the MAC are modified. So, many disturbed messages, which cannot be corrected by repetition, can be recovered -- at the cost of trust in the message. This paper introduces the quantified unit of trust in a message and presents the results of simulations, showing a significant improvement of the acceptance rate of the cryptographic verification.