Certificateless proxy multi-signature

Proxy multi-signature allows a group of original signers to delegate their signing capabilities to a proxy signer in such a way that the proxy signer can sign messages on behalf of the group of original signers. Existing constructions of proxy multi-signatures are based on traditional Public Key Infrastructure or Identity-based Public Key Setting, but the former needs certificates which bring about many certificate management problems, and the latter has a drawback of key escrow. In contrast to the existing constructions, in this paper, we study proxy multi-signature in Certificateless Public Key Cryptography (CL-PKC) which combines the advantages of both certificate-based and identity-based cryptosystems as it avoids the use of certificates and does not suffer from key escrow. We provide the definition and the security model for Certificateless Proxy Multi-Signature (CLPMS), and propose the first CLPMS scheme which is proved to be secure in the random oracle model under the computational Diffie-Hellman assumption. Our scheme is computationally efficient and has the property that the size of a proxy multi-signature is independent of the number of the original signers.