W-OTS+ - Shorter signatures for hash-based signature schemes

Abstract

We present W-OTS+, a Winternitz type one-time signature scheme (W-OTS). We prove that W-OTS+ is strongly unforgeable under chosen message attacks in the standard model. Our proof is exact and tight. The first property allows us to compute the security of the scheme for given parameters. The second property allows for shorter signatures than previous proposals without lowering the security. This improvement in signature size directly carries over to all recent hash-based signature schemes. I.e. we can reduce the signature size by more than 50% for XMSS+ at a security level of 80 bits. As the main drawback of hash-based signature schemes is assumed to be the signature size, this is a further step in making hash-based signatures practical. © 2013 Springer-Verlag Berlin Heidelberg.