A Strand Space Approach to Provable Anonymity

Abstract

We formalize in the strand space theory the notion of provable anonymity. Bundle in a strand space is used to formalize a session of a protocol. Behaviors of an observer can then be formalized as extensions of a bundle. Reinterpretation function can be naturally derived from the mapping from one message term of an edge of a bundle in a strand space to that in another strand space. We formally define observational equivalence on bundles and use it to formalise anonymity properties. The novelty of our theory lies in the observational model and the construction of reinterpretation functions in the strand space theory. We build our theory in Isabelle/HOL to achieve a mechanical framework for the analysis of anonymity protocols.

A Framework for Formal Analysis of Anonymous Communication Protocols

“…Its feasibility is illustrated through two case studies of the Crowds and Onion Routing protocols. In order to make the strand space model satisfy the special needs of anonymity analysis, the anonymity formalization framework based on strand space model was extended [19][20][21]. In addition, a method for formalizing anonymity based on protocol composition logic (PCL) is proposed, which extends the application of PCL [22].…”