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.