Feedback-Based Collaborative Secrecy Encoding Over Binary Symmetric Channels

In this paper, we propose a feedback scheme for transmitting secret messages between two legitimate parties, over an eavesdropped communication link. Relative to Wyner´s traditional encoding scheme, our feedback-based encoding often yields larger rate-equivocation regions and achievable secrecy rates. More importantly, by exploiting the channel randomness inherent in the feedback channels, our scheme achieves a strictly positive secrecy rate even when the eavesdropper´s channel is less noisy than the legitimate receiver´s channel. All channels are modeled as binary and symmetric. We demonstrate the versatility of our feedback-based encoding method by using it in three different configurations: the stand-alone configuration, the mixed configuration (when it combines with Wyner´s scheme), and the reversed configuration. Depending on the channel conditions, significant improvements over Wyner´s secrecy capacity can be observed in all configurations.