Paper 2005/074

Computationally sound implementations of equational theories against passive adversaries

Mathieu Baudet and Vëronique Cortier and Steve Kremer

Abstract

In this paper we study the link between formal and cryptographic models for security protocols in the presence of a passive adversary. In contrast to other works, we do not consider a fixed set of primitives but aim at results for an arbitrary equational theory. We define a framework for comparing a cryptographic implementation and its idealization w.r.t. various security notions. In particular, we concentrate on the computational soundness of static equivalence, a standard tool in cryptographic pi calculi. We present a soundness criterion, which for many theories is not only sufficient but also necessary. Finally, we establish new soundness results for the Exclusive Or, as well as a theory of ciphers and lists.