International Association
for Cryptologic Research

In this note we assess the efficiency of a SIDH-based digital signature built on a diminished variant of a recent identification protocol proposed by Basso et al. Despite the devastating attacks against the mathematical problem underlying SIDH, this identification protocol remains secure, as its security is backed by a different (and more standard) isogeny-finding problem. We conduct our analysis by applying some known cryptographic techniques to decrease the signature size by about 70% for all parameter sets (obtaining signatures of approximately 21 KB for SIKEp434). Moreover, we propose a minor optimisation to compute many isogenies in parallel from the same starting curve. Our assessment confirms that the problem of designing a practical isogeny-based signature scheme remains largely open. However, concretely determine the current state of the art which future optimisations can compare to appears to be of relevance for a problem which has witnessed only small steps towards a solution.