Design And Analysis Of Two Threshold Proxy Signature Schemes

The proxy signature allows proxy signers to sign messages on behalf of the original signer without exposing the original signer's private key. Combining with the idea of threshold, K. Zhang designed a (t, n) threshold proxy signature scheme, in which the proxy signing key is shared by a group of n proxy signers in such a way that any t or more proxy signers can cooperatively derive the proxy signing key to sign messages on behalf of the original signer. It can be widely used in electronic commerce for its good property.In this article, we mainly study two threshold proxy signature schemes. First, we propose a new threshold proxy signature scheme based on the RSA cryptosystem. Compared with the schemes based on the discrete logarithm or the RSA cryptosystem, it requires less computations and communications and satisfies all the proxy requirements. Besides, during the communications, it doesn't need a secure channel and can detect the malicious proxy signers in time.Secondly, we analyze and point out the main problems in the C-C scheme and C-K-L scheme. We made an improvement to overcome the weakness and propose a new forward secure threshold proxy signature scheme according to the improvement. The scheme satisfies the basic requirement of the threshold proxy signature and doesn't need key distribution center during the generation of signing keys. Besides, it can achieve the asynchronous of the original signer and the proxy signer during the key generation step to enhance the security. Finally, we propose an electronic commerce transaction system based on the forward secure threshold proxy signature scheme.