  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 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 (DM) case, we establish inner and outer bounds on the
capacity-equivocation region. The inner bound is based on a combination of
Willems's coding scheme, noise injection 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 show that, under
certain conditions, these bounds agree in some extreme cases of cooperation
between the encoders. We illustrate our results through some numerical
examples.
