Abstract: This paper presents a joint nominative proxy signature scheme by combining the methods of nominative proxy signatures and multi-signatures, which can be used to solve the problem of signing on a document by multiple original signers efficiently. Also, an improved scheme is further proposed to protect the proxy’s privacy, and the identity of the proxy signer is hidden behind an alias, with only a trusted registration center revoking his or her identity.

Key words: nominative proxy signature, joint nominative proxy signature, privacy protection