Tightly Secure Signatures from the RSA Assumption

Abstract

Abstract. In this paper, we construct a new RSA-based signature scheme that is tightly secure in the random oracle model. The number of random oracles used in this scheme is less than that of all previous schemes with same security guarantee. We then show that for any PPT adversary there exists a concrete hash function from indistinguishability obfuscation that can replace the random oracle with keeping security. The same statement can be proven for the signatures of Coron.