Proxiable Designated Verifier Signature

概要

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Designated Verifier Signature (DVS) guarantees that only a verifier designated by a signer can verify the "validity of a signature". In this paper, we propose a new variant of DVS; Proxiable Designated Verifier Signature (PDVS) where the verifier can commission a third party (i.e., the proxy) to perform some process of the verification. In the PDVS system, the verifier can reduce his computational cost by delegating some process of the verification without revealing the validity of the signature to the proxy. In all DVS systems, the validity of a signature means that a signature satisfies both properties that (1) the signature is judged "accept" by a decision algorithm and (2) the signature is confirmed at it is generated by the signer. So in the PDVS system, the verifier can commission the proxy to check only the property (1). In the proposed PDVS model, we divide verifier's secret keys into two parts; one is a key for performing the decision algorithm, and the other is a key for generating a dummy signature, which prevents a third party from convincing the property (2). We also define security requirements for the PDVS, and propose a PDVS scheme which satisfies all security requirements we define.