Improved certificateless multi-proxy signature

Multi-proxy signature is a scheme that an original signer delegates his or her signing capability to a proxy group. In the scheme, only the cooperation of all proxy signers in the proxy group can create a signature on behalf of the original signer. Jin and Wen firstly defined the formal security model of certificateless multi-proxy signature (CLMPS) and proposed a concrete CLMPS scheme. However, their construction has three problems: the definition of the strengthened security model is inaccurate, the concrete signature scheme has a security flaw, and the proof of the security is imperfect. With further consideration, a remedial strengthened security model is redefined, and an improved scheme is also proposed, which is existentially unforgeable against adaptively chosen-warrant, chosen-message and chosen-identity attacks in the random oracles. In this condition, the computational Diffie-Hellman (CDH) assumption is used to prove full security for our CLMPS scheme.