We propose a new notion of an entrusted undeniable signature which is a variant of the undeniable signature. Also we propose a provably entrusted undeniable signature whose security can be proved. The proposed entrusted undeniable signature is a new type of undeniable signature in which the signer confirms his(her) signature to any verifier without the help of court but the verifier can't run the disavowal protocol in the undeniable signature which only court can run to solve the dispute later. The proposed scheme is constructed by a combination of the undeniable signature and zero-knowledge interactive proof system. The proposed provably entrusted undeniable signature is much the same as our entrusted undeniable signature but using the public key residue cryptosystem, which is polynomially secure, for the commitment scheme.
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