TWC: Medium: Limits and Algorithms for Covert Communications

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Security and privacy are prominent concerns in modern communications. Although cryptographic approaches have been widely studied to protect a message's content from deciphering by an eavesdropper, there are many times when hiding the very existence of the communication is critical. The hiding of communication, termed covert (private) communication, is important in many domains such as covert military operations, and removing the ability of users to be tracked in their everyday activities. It is also important to study how to limit such covert communications, for example between parties such as terrorists organizing activities to do harm. This project is focused on understanding what the potential is for covert communications, i.e., how much information can be communicated without detection, and the development of practical schemes for providing covert communications as well as techniques for limiting such communication. Covert communication has been historically considered from a practical perspective. For example spread spectrum communications was developed as a wireless communication technique to provide covert communications. Systems such as Tor were developed to provide covertness in the Internet. This project focuses on the systematic investigation of the fundamental limits in providing covertness in communications at the physical, the network, and the application layers of modern communication networks. It will explore the use of noise in wireless channels and timing variabilities in networks to implement covert communications. This includes the development of fundamental limits in terms of the amount of information that can be conveyed covertly without being detected, while accounting for uncertainties among all participants. The project will also focus on the development of fundamental limits for application-level covert communications using voice over IP and image posting on social networks. A key consideration will be how these limits can be impacted by changes in the operating environment, including those changes made intentionally by allies of the communicating parties to enhance covert communications or those made by adversaries of the communicating parties to limit such. A second focus will be on the design and evaluation of algorithms that ensure communicating parties achieve these limits and another set of algorithms that ensure these parties are detected when they attempt to exceed the limits.