Post-quantum Security of Fiat-Shamir Signatures Jelle Wijnand Don Abstract: We propose a proof method that aims to show that the Fiat-Shamir proof system is SP-extractable (statement preserving) in the quantum random oracle model, if the underlying sigma-protocol has perfect unique responses. We furthermore prove that a signature scheme which is based on a Fiat-Shamir proof system that is SP-extractable, is existentially unforgeable for a quantum adversary.