An achievable region for the Wiretap multiple-access channel with common message

We derive a rate region which is achievable by the Wiretap MAC with Common Message under the strong secrecy criterion. We follow Devetak´s approach to establishing strong secrecy. Using the concentration of the normed sum of bounded i.i.d. random variables around its mean, it is possible to show the existence of a code where the channel outputs at the eavesdropper are almost independent of the messages. The encoders may use a certain amount of common randomness. We give the example of a channel where the availability of common randomness is necessary for secret transmission.