Proxy Ring Signature: Formal Definitions, Efficient Construction and New Variant

Proxy ring signatures allow proxy signer to sign messages on behalf of the original signer while providing anonymity. In this paper, we give the first formal security definitions and notions of proxy ring signatures. Subsequently, we propose a short proxy ring signature scheme, with rigorous security proofs. It is more efficient than the existing proxy ring signature schemes. Finally, we propose a new kind of proxy ring signatures. Existing proxy ring signatures in the literature provide anonymity for proxy signer only. We extend the notion to support anonymity for original signer as well. We give an efficient and secure instantiation of it.