  In this paper, we study the problem of secret communication over a
multiple-access channel with a common message. Here, we assume that two
transmitters have confidential messages, which must be kept secret from the
wiretapper (the second receiver), and both of them have access to a common
message which can be decoded by the two receivers. We call this setting as
Multiple-Access Wiretap Channel with Common message (MAWC-CM). For this
setting, we derive general inner and outer bounds on the secrecy capacity
region for the discrete memoryless case and show that these bounds meet each
other for a special case called the switch channel. As well, for a Gaussian
version of MAWC-CM, we derive inner and outer bounds on the secrecy capacity
region. Providing numerical results for the Gaussian case, we illustrate the
comparison between the derived achievable rate region and the outer bound for
the considered model and the capacity region of compound multiple access
channel.
