Identity-Based Directed Signature Scheme without Bilinear Pairings

Abstract

In a directed signature scheme, a verifier can exclusively verify the signatures designated to himself, and shares with the signer the ability to prove correctness of the signature to a third party when necessary. Directed signature schemes are suitable for applications such as bill of tax and bill of health. This paper studies directed signatures in the identity-based setting. We first present the syntax and security notion that includes unforgeability and invisibility, then propose a concrete identity-based directed signature scheme from bilinear pairings. We then prove our scheme existentially unforgeable under the computational Diffie-Hellman assumption, and invisible under the decisional Bilinear Diffie-Hellman assumption, both in the random oracle model.