Non-adaptive Group-Testing Aggregate MAC Scheme

This paper applies non-adaptive group testing to aggregate message authentication code (MAC) and introduces non-adaptive group-testing aggregate MAC. After formalization of its syntax and security requirements, simple and generic construction is presented, which can be applied to any aggregate MAC scheme formalized by Katz and Lindell in 2008. Then, two instantioations of the construction is presented. One is based on the aggregate MAC scheme by Katz and Lindell and uses addition for tag aggregate. The other uses cryptographic hashing for tag aggregate. Provable security of the generic construction and two instantiations are also discussed

Another Look at Tightness

Abstract. We examine a natural, but non-tight, reductionist security proof for deterministic message authentication code (MAC) schemes in the multi-user setting. If security parameters for the MAC scheme are selected without accounting for the non-tightness in the reduction, then the MAC scheme is shown to provide a level of security that is less than desirable in the multi-user setting. We find similar deficiencies in the security assurances provided by non-tight proofs when we analyze some protocols intheliteratureincludingonesfor networkauthentication and aggregate MACs. Our observations call into question the practical value of non-tight reductionist security proofs. We also exhibit attacks on authenticated encryption schemes, disk encryption schemes, and stream ciphers in the multi-user setting.