Cryptanalysis of an efficient proof of knowledge of discrete logarithm

Abstract

At PKC 2005, Bangerter, Camenisch and Maurer proposed an efficient protocol to prove knowledge of discrete logarithms in groups of unknown order. We describe an attack that enables the verifier to recover the full secret with essentially no computing power beyond what is required to run the protocol and after only a few iterations of it. We also describe variants of the attack that apply when some additional simple checks are performed by the prover. © International Association for Cryptologic Research 2006.