Communication and Third Parties: Costs, Cues, and Confidentiality

Communication and Third Parties: Costs, Cues, and Confidentiality by Krishnan Eswaran Doctor of Philosophy in Engineering—Electrical Engineering and Computer Sciences and the Designated Emphasis in Communication, Computation, and Statistics University of California, Berkeley Professor Michael Gastpar, Chair This thesis tells the story of Alice and Bob, who wish to share information. However, Alice and Bob, motivated either by self-interest or simply good manners, also wish to respect constraints imposed by Candice, Damon, or Eve, who may be lurking in the background. This thesis takes an information-theoretic approach to determine the rates at which Alice and Bob can communicate while satisfying the constraints imposed by these third parties. The constraints in this thesis are inspired by wireless communication, in which multiple users share a common medium. Signals over a common medium can interfere with one another, so a case study is introduced that models one aspect of this problem: Alice must send a message to Bob such that she does not interfere with communication from Candice to Damon. Furthermore, Candice and Damon are unaware of Alice and Bob, so there is no direct way for Alice to learn how much interference she causes. However, by relying on cues gained from eavesdropping on feedback signals from Damon to Candice, strategies are introduced that enable Alice to communicate with Bob and adaptively control