Computationally Efficient Covert Communication

Abstract: In this paper, we design the first computationally efficient codes for simultaneously reliable and covert communication over Binary Symmetric Channels (BSCs). Our setting is as follows: a transmitter Alice wishes to potentially reliably transmit a message to a receiver Bob, while ensuring that the transmission taking place is covert with respect to an eavesdropper Willie (who hears Alice's transmission over a noisier BSC). Prior works show that Alice can reliably and covertly transmit O(\sqrt{n}) bits over n channel uses without any shared secret between Alice and Bob. One drawback of prior works is that the computational complexity of the codes designed scales as 2^{\Theta(\sqrt{n})}. In this work we provide the first computationally tractable codes with provable guarantees on both reliability and covertness, while simultaneously achieving the best known throughput for the problem.