An Identity-Based Strong Designated Verifier Dual-Signature Scheme With Constrained Delegatability

Verifying the correctness of outsourcing computation is both cumbersome and expensive, and it also requires third-party verification if auditing or arbitrating is involved. Due to its complexities, users are likely to reoutsource the verification workload to trusted third-party vendors. Multiple outsourcing tasks increase the expense of communications and expose more vulnerabilities. To address this problem, we propose an identity-based strong designated verifier dual-signature scheme with constrained delegatability. The particular innovation lies in two aspects. First, in cases where there are multiple parties involved, users can autonomously designate verifiers. Second, we first present the concept of constrained delegatability, where a signature cannot be delegated to any other than the cloud service provider. In this scheme, a user can specify a trusted verifier for the dual signature co-signed by both him and the service provider on the outsourcing result. The provider cannot designate anyone else to check the signature. The proposed scheme is provably secure based on elliptic curve bilinear pairing and the hardness assumption of computational Diffie–Hellman and bilinear Diffie–Hellman problems. Moreover, our scheme simplifies the outsourcing process and reduces the total computational costs and communication time compared to previously reported ones.