Feedback in Soft Input Decryption

This paper develops further the idea of use of Soft Input Decryption. The function of Soft Input Decryption is to integrate decryption into the decoding process. In this paper it is shown how Soft Input Decryption can be enhanced using feedback from the channel decoder. In this way, the cooperation between channel coding and cryptography is further develops. The effect of the feedback is explained on an example of the trellis diagram. Like in Soft Input Decryption, also in feedback method is the usage of reliability L-values of SISO channel decoder of great importance. Theoretical analysis, as well as results of computer simulations have been presented and discussed. Key-Words: Soft Input Decryption, feedback, L-values, cryptographic check values, MAP, SISO Channel Decoding, trellis