We consider a scenario in which Alice asynchronously communicates with Bob over a Discrete Memoryless Channel (DMC) while escaping detection from an adversary who observes their communication through another DMC. Specifically, Alice transmits codewords of length n and chooses the transmission epoch T uniformly at random among N available time epochs, where N ≫ n. This deliberate symbol level-asynchronism forces the adversary to monitor a window of size N′ much larger than the codeword length n, and results in an increased covert throughput compared to the scenario without asynchronism. Our result generalizes a previous work in which asynchronism was introduced at the codeword level, i.e., having Alice choose a transmission window among non-overlapping windows of length n.
['Keerthi Suria Kumar Arumugam', 'Matthieu R. Bloch']
Keyless asynchronous covert communication