Server (Prover/Signer)-Aided Verification of Identity Proofs and Signatures

Discrete log based identiication and signature schemes are well-suited to identity proof and signature generation, but not suitable for veriication, by smart cards, due to their highly asymmetric computational load between the prover/signer and the veriier. In this paper, we present very eecient and practical protocols for fast veriication in these schemes, where the veriier with limited computing power performs its computation fast with the aid of the powerful prover/signer. The proposed protocols require very small amounts of computation and communication. The prover/signer only needs to perform a few modular exponentiations in real-time and the two interacting parties only need to communicate a few long numbers. Using the proposed prover-aided veriication (PAV) protocol, the veriier can perform the Schnorr-like identiication scheme almost as fast as the Guillou-Quisquater scheme. We generalize the PAV protocol into the signer-aided veriication (SAV) protocol, which can be used for veriication of any public function.