No Certificate Of Threshold Proxy Signature

Digital signature is a section of messages which can confirm the identity of a signer and the truth what he have signed. It is widely used in authentication, authoriza-tion and nonrepudiation. Further, it plays a key role in many security systems, for example, e-government systems, e-commerce systems.In the real world, the power often can be passed. That is one can partially or fully authorize other people to exercise power on behalf of himself, for instance, entrusting other people to sign files for himself. Proxy signature technique is a kind of digital signature which can pass the power. Proxy signature allows the original signer to authorize the signing capability to a person he trusts, called the proxy signer, who can make files signed instead of him, and the receiver can verify the signature is agreed with and authorized by the original signer. According to various actual requirements, pepple have put forward different kinds of proxy signature, such as proxy blind signature, threshold proxy signature, proxy multi-signature and so on. Threshold proxy signature is proposed to disperse the proxy signers’power.(t, n) threshold proxy signature is a signature in which proxy signature key is divided into n proxy signers, and is then used to generate partial proxy signature by each proxy signer, and the final signature can only be cooperatively generated by at least t proxy signers.Certificateless public key cryptography is a novel cryptography and represents an interesting and useful balance between the conventional public key cryptography based on certificate and identity-based cryptography, which not only can eliminate the need of certificate in traditional public key cryptography, but also can resolve the key escrow problem in identity-based cryptography.This paper mainly discusses certificateless threshold proxy signature schemes, which not only have the properties of certificateless cryptography, but also possess the merits of threshold proxy signature. The main contents are as followes.1. Based on bilinear pairing, a safe threshold proxy signature scheme is posed by combining with certificateless public key cryptography. The new scheme eliminates the key escrow problem in identity-based cryptography, has strong unforgeability and strong nonrepudiation, and can resist original signer change attack, besides the proxy signers cannot change the scheme’s threshold value t, so it satisfies the security requirements of threshold proxy signature.2. Through analysis towards an identity-based threshold proxy signature scheme, it is found that the signature can only be verified with public keys of the designated actual proxy signers who participate in generating the signature in the signature process, which limits the application of the scheme. To make wider use, full (t, n) threshold proxy signature is proposed. It satisfies the following requirements:any t proxy signers’ signature can all be verified with the same equality, can all be verified with the public information of proxy group and it has nothing to do with the designated t proxy signers who generate the signature when verifying the signature. Then we present a full (t,n) threshold proxy signature scheme by using the certificateless public key cryptography. The new scheme not only can resist collusion attack, frame attack and public-key substitute attack, but also avoid the complex certificate management of the original scheme, besides it satisfies the security requirements of threshold proxy signature.