Identity-based zero-knowledge

We introduce and define the notion of identity-based zeroknowledge, concentrating on the non-interactive setting. In this setting, our notion allows any prover to widely disseminate a proof of a statement while protecting the prover from plagiarism in the following sense: although proofs are transferable (i.e., publicly verifiable), they are also bound to the identity of the prover in a way which is recognizable to any verifier. Furthermore, an adversary is unable to change this identity (i.e., to claim the proof as his own, or to otherwise change the authorship), unless he could have proved the statement on his own. While we view the primary contribution of this work as a formal definition of the above notion, we also explore the relation of this notion to that of non-malleable (non-interactive) zero-knowledge. On the one hand, we show that these two notions are incomparable: that is, there are proof systems which are non-malleable but not identity-based, and vice versa. On the other hand, we show that a proof system of either type essentially implies a proof system of the other type.