A new multiple access wiretap channel model

A new model for the two-user multiple-access wiretap channel is considered. In this model, the legitimate (main) channel is a discrete memoryless channel (DMC), and the wiretapper chooses a fixed-length subset of the channel uses where she has perfect access to the transmitted symbols of the both users, while observing the remainder of the transmitted codewords through a second DMC. As such, it generalizes the existing multiple-access wiretap channel models and extends the recently proposed new wiretap channel model to a multiple access setting. An achievable strong secrecy rate region for the model is derived. The achievability is established by solving a dual multi-terminal secret key agreement problem in the source model, where two independent sources are communicating confidential keys to a common decoder over a public channel in the presence of a compound wiretapping source. The secrecy of the two keys in the dual source model is established by deriving a lemma which provides a doubly exponential convergence rate for the probability of the keys being uniform and independent from the public discussion and the wiretapping source observation.