MAC with Partially Cooperating Encoders and Security Constraints

We study a special case of Willems's two-user multiaccess channel with partially cooperating encoders from security perspective. This model differs from Willems's setup in that only one encoder, Encoder 1, is allowed to conference, Encoder 2 does not transmit any message, and there is an additional passive eavesdropper from whom the communication should be kept secret. For the discrete memoryless case, we establish inner and outer bounds on the rate-equivocation region. Furthermore, we show that these bounds coincide in the case of perfect secrecy, and so we characterize fully the secrecy capacity. For the Gaussian model, we establish lower and upper bounds on the perfect secrecy rate. We also show that these bounds agree in some extreme cases of cooperation between encoders. We illustrate our results through some numerical examples.