Subliminal channels for transferring signatures: Yet another cryptographic primitive

This paper considers the subliminal channel, hidden in an identification scheme, for transferring signatures. We observe the direct parallelization of the Fiat-Shamir identification scheme has a subliminal channel for the transmission of the digital signature. A positive aspect of this hidden channel supplies us how to transfer signatures without secure channels. As a formulation of such application, we introduce a new notion called privately recordable signature. The privately recordable signature is generated in an interactive protocol between a signer and a verifier, and only the verifier can keep the signatures although no third adversary can record the signatures. In this scheme, then the disclosure of the verifier's private coin turns the signer's signature into the ordinary digital signature which is verified by anybody with the singer's public key. The basic idea of our construction suggests the novel primitive that a transferring securely signatures without secret channels could be constructed using only one-way function (without trapdoor).