# Designated Verifier Proofs and Their Applications

## Abstract

For many proofs of knowledge it is important that only *the verifier designated by the confirmer* can obtain any conviction of the cor- rectness of the proof. A good example of such a situation is for undeniable signatures, where the confirmer of a signature wants to make sure that only the intended verifier(s) in fact can be convinced about the validity or invalidity of the signature.

Generally, authentication of messages and off-the-record messages are in conflict with each other. We show how, using designation of verifiers, these notions can be combined, allowing authenticated but privat con- versations to take place. Our solution guarantees that *only* the specified verifier can be convinced by the proof, even if he shares all his secret information with entities that want to get convinced.

Our solution is based on *trap-door commitments* [4], allowing the desig- nated verifier to open up commitments in any way he wants. We demon- strate how a trap-door commitment scheme can be used to construct designated verifier proofs, both interactive and non-interactive. We ex- amplify the verifier designation method for the confirmation protocol for undeniable signatures.

## Keywords

Commitment Scheme Logical Entity Computational Entity Undeniable Signature Zero Knowledge Proof## References

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