Attacks on secure logging schemes

Abstract

We present four attacks on three cryptographic schemes intended for securing log files against illicit retroactive modification. Our first two attacks regard the LogFAS scheme by Yavuz et al. (Financial Cryptography 2012), whereas our third and fourth attacks break the BM- and AR-FssAgg schemes by Ma (AsiaCCS 2008). All schemes have an accompanying security proof, seemingly contradicting the existence of attacks. We point out flaws in these proofs, resolving the contradiction.