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arXiv · 1803.06007

Covert Communication over a K-User Multiple Access Channel

Keerthi Suria Kumar Arumugam·Matthieu R. Bloch
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Abstract

We consider a scenario in which $K$ transmitters attempt to communicate covert messages reliably to a legitimate receiver over a discrete memoryless MAC while simultaneously escaping detection from an adversary who observes their communication through another discrete memoryless MAC. We assume that each transmitter may use a secret key that is shared only between itself and the legitimate receiver. We show that each of the $K$ transmitters can transmit on the order of $\sqrt{n}$ reliable and covert bits per $n$ channel uses, exceeding which, the warden will be able to detect the communication. We identify the optimal pre-constants of the scaling, which leads to a complete characterization of the covert capacity region of the $K$-user binary-input MAC. We show that, asymptotically, all sum-rate constraints are inactive unlike the traditional MAC capacity region. We also characterize the channel conditions that have to be satisfied for the transmitters to operate without a secret key.

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Keerthi Suria Kumar Arumugam, Matthieu R. Bloch. 2018-03-15. Covert Communication over a K-User Multiple Access Channel. https://arxiv.org/abs/1803.06007

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