Identity-based Universal Designated Verifier Signature Proof System

The notion of Universal Designated Verifier Signature (UDVS), introduced by Steinfeld et al. in Asiacrypt 2003, allows any holder of a signature to convince any designated verifier that the signer indeed generated the signature without revealing the signature itself, while the verifier cannot transfer the proof to convince anyone else of this fact. Such signature schemes can protect the privacy of signature holders and have applications in certification systems. Very recently, as pointed out by Baek et al. in Asiacrypt 2005, one significant inconvenience of all existing UDVS schemes is that they require the designated verifier to create a public key using the signer’s public key parameter and have it certified to ensure the resulting public key is compatible with the setting that the signer provided. This is unrealistic in some situations where the verifier is not willing to go through such setup process. Baek et al. introduced the concept of Universal Designated Verifier Signature Proof (UDVSP) to solve this problem. In this paper, we first introduce the idea of identity-based (ID-based) UDVSP system. Furthermore, we point out that the algorithm “Signature Transformation ST ” of the UDVSP defined by Baek et al. can be eliminated, which results in a more efficient UDVSP system. We present two ID-based UDVSP systems based on bilinear pairings, and provide the security proofs of our systems in the random oracle model.