EliMAC: Speeding Up LightMAC by around 20%

Abstract

Universal hash functions play a prominent role in the design of message authentication codes and the like. Whereas it is known how to build highly efficient sequential universal hash functions, parallel non-algebraic universal hash function designs are always built on top of a PRP. In such case, one employs a relatively strong primitive to obtain a function with a relatively weak security model. In this work, we present EliHash, a construction of a parallel universal hash function from non-compressing universal hash functions, and we back it up with supporting security analysis. We use this construction to design EliMAC, a message authentication code similar to LightMAC. We consider a heuristic instantiation of EliMAC with roundreduced AES, and argue that this instantiation of EliMAC is much more efficient than LightMAC, it is around 21% faster, and additionally allows for precomputation of the keys, albeit with a stronger assumption on the AES primitive than in LightMAC. These observations are backed up with an implementation of our scheme.