Identity-Based Strong Designated Verifier Signature Scheme with Full Non-Delegatability

Jakobsson et al. first proposed the notions of designated verifier signature (DVS) and an enhanced version, strong designated verifier signature (SDVS) that only the designated verifier can verify the signature´s validity. Since then, many improved schemes and variants have been proposed. In 2005, Lipmaa et al. introduced a delegation-attack and proposed a corresponding security concept, namely non-delegatability, which means that both the signer and the designated verifier can not delegate signing right to a third party to generate a valid signature. In this paper, we present a stronger security notion for the SDVS schemes, full non-delegatability, which not only needs the non-delegatability of signing, but also requires that non-delegatability of verifying. And we also analyze some previous SDVS schemes and find that all of them are not secure under the new security notion. At last, we propose an improved SDVS scheme based on identity (ID-SDVS). The proposed scheme is provably secure under the new security notion in the random oracle model.