The Wiretap Channel with Generalized Feedback: Secure Communication and Key Generation

Submitted to IEEE Trans. Information TheoryInternational audienceIt is a well-known fact that feedback does not increase the capacity of point-to-point memoryless channels, however, its effect in secure communications is not fully understood yet. In this work, two achievable schemes for the wiretap channel with generalized feedback are presented. One of the schemes, which is based on joint source-channel coding, correlates the codewords to be transmitted with the feedback signal in the hope of "hiding" them from the eavesdropper's observations. The other scheme, which uses the feedback signal to generate a shared secret key between the legitimate users, encrypts the message to be sent at the bit level. These schemes recover previous known results from the literature, thus they can be seen as a generalization and hence unification of several results in the field. Additionally, we present new capacity results for a class of channels and, for the Gaussian wiretap channel with noisy feedback, the schemes are shown to achieve positive secrecy rates even in unfavorable scenarios where the eavesdropper experiences much better channel conditions than the legitimate user