Identity-Based Chameleon Signature Schemes over Lattices

Chameleon Signature (CS) is an ideal designated verifier signature, it realizes non-transferability using chameleon hash function, makes any third party distrust the content disclosed by a designated verifier, and avoids the shortcoming of online interactive verification of undeniable signature. In addition to non transferability, CS also should satisfy unforgeability, deniability, non-repudiation for the signer, and so on. solve the problems that cryptosystems based on the number theory problems such as integer factorization discrete logarithm cannot resist quantum computing attacks and users rely on digital certificates, an Identity Based Chameleon Signature (IBCS) over lattices is proposed, the new scheme avoids the security vulnerability that the signer cannot reject the forged signature of the designated verifier in the existing schemes, and reduces the transmission cost of the final signature from square to linear; Furthermore, to solve the failure problem non-transferability in the arbitration phase, an IBCS scheme with exposure-freeness over lattices is proposed, the new scheme enables the signer to reject a forged signature of any adversary without exposing the real message. Particularly, based on the hardness of the small integer solution problem, both schemes can be proved secure in the random oracle model.