Inductive methods and contract-signing protocols

Abstract

Garay, Jakobsson and MacKenzie introduced the notion of abuse-free distributed contract-signing: at any stage of the protocol, no participant Ahas the ability to prove to an outside party, that A has the power to choose between completing the contract and aborting it. We study a version of this property, which is naturally formulated in terms of game strategies, and which we formally state and prove for a two-party, optimistic contract-signing protocol. We extend to this setting the formal inductive proof methods previously used in the formal analysis of simpler, trace-based properties of authentication protocols.