Combination of Channel Coding and Cryptography

We have launched a new research area which combines cryptographic methods with new developments of channel coding. Modern methods of channel encoding and decoding, which supply error recognition and recovery, are using more and more soft input and soft output (SISO). That means that bit „1“ and „0“ is replaced by real reliability numbers, which correspond to the probability that a received value was a „1“ or „0“ before transmission. We apply cryptographic mechanisms for encryption and digital signatures, which use such real reliability numbers as input data instead of bits „1“ and „0“. By this method, the error rate after decryption of data or verifi cation of digital signatures can be strongly reduced. One single error bit in an encrypted message or in a digital signature spoils the complete message. The automatic correction of false signatures or decrypted messages is therefore specifi cally important and interesting when transmission is performed over very noisy channels, or when real time or one way (simplex) transmission is done not allowing for repetition of the message in the case that they are not received correctly.