Research On Certificateless Proxy Signature

The concept of Certificateless Public Key Cryptography was introduced by Al-Riyami and Paterson in ASIACRYPT 2003. It is a hybrid between traditional public key infrastructure and Identity-based Public Key Cryptography. It eliminated the problem of the certificate management in the certificate-based public key cryptosystem and overcome the key-escrow problem of identity-based public key cryptography but preserved all of its advantages.Proxy signature makes an original signer delegate his signing capacity to a proxy signer true. A proxy signature scheme allows an entity called original signer to delegate signing capabilities to other participants called proxy signers. Then the proxy signer can generate proxy signature on behalf of the original signer. Recently, the research on certificateless digital signature has obtained the certain achievement, but there is very few literatures on certificateless proxy signature.In this paper, we give the formal definition of certificateless proxy signature scheme, and present the security model of the certificateless proxy signature. Then we construct a provable secure certificateless proxy signature scheme and also provide exact security proof of the proposed scheme in the random oracle model based on CDH problem. Our proof is tight without using Forking Lemma. Then we combine the concept of universal designate verifier signature and proxy signature, proposes the concept of certificateless universal designated verifier proxy signature. We also construct a provable secure scheme and prove that the proposed scheme is existential unforgeable against the adaptive chosen message attack in the random oracle model.