We study a special case of Willems's two-user multi-access channel with partially cooperating encoders from a security perspective. This model differs from Willems's setup in the following aspects — 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 (DM) case, we establish inner and outer bounds on the capacity-equivocation region. The inner bound is established by a careful combination of Willems's coding scheme, noise injection scheme and additional binning that provides randomization for security. For the memoryless Gaussian model, we establish lower and upper bounds on the secrecy capacity. We also studied some extreme cases of cooperation between the encoders and showed that, under certain conditions, these bounds coincide.
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