Invariant Signatures and Non-Interactive Zero-Knowledge Proofs are Equivalent (Extended Abstract)
The standard definition of digital signatures allows a document to have many valid signatures. In this paper, we consider a subclass of digital signatures, called invariant signatures, in which all legal signatures of a document must be identical according to some polynomial-time computable function (of a signature) which is hard to predict given an unsigned document. We formalize this notion and show its equivalence to non-interactive zero-knowledge proofs.