Out-of-Band Covert Channels—A Survey

A novel class of covert channel, out-of-band covert channels, is presented by extending Simmons' prisoners' problem. This new class of covert channel is established by surveying the existing covert channel, device pairing and side channel research. Terminology as well as a taxonomy for out-of-band covert channels is also given. Additionally, a more comprehensive adversarial model based on a knowledgeable passive adversary and a capable active adversary is proposed in place of the current adversarial model, which relies on an oblivious passive adversary. Lastly, general protection mechanisms are presented and an argument for a general measure of "covertness" to effectively compare covert channels is given.