Abstract. We propose GMSS, a new variant of the Merkle signature scheme. GMSS is the first Merkle-type signature scheme that allows a cryptographically unlimited (2 80) number of documents to be signed with one key pair. Compared to recent improvements of the Merkle signature scheme, GMSS reduces the signature size as well as the signature generation cost. Keywords: Merkle signatures, post-quantum cryptography, SSL. 1

Public key cryptography is widely used to secure transactions over the Internet. However, advances in quantum computers threaten to undermine the security assumptions upon which currently used public key cryptographic algorithms are based. In this paper, we provide a survey of some of the public key cryptographic algorithms that have been developed that, while not currently in widespread use, are believed to be resistant to quantum computing based attacks and discuss some of the issues that protocol designers may need to consider if there is a need to deploy these algorithms at some point in the future.