We speed up the isogeny-based "SeaSign'' signature scheme recently proposed by De Feo and Galbraith. The core idea in SeaSign is to apply the "Fiat–Shamir with aborts'' transform to the parallel repeated execution of an identification scheme based on CSIDH. We optimize this general transform by allowing the prover to not answer a limited number of said parallel executions, thereby lowering the overall probability of rejection. The performance improvement ranges between factors of approximately 4.4 and 65.7 for various instantiations of the scheme, at the expense of roughly doubling the signature sizes
