The Study Of Efficient Ring Signature

Digital signature is one of the key tools in information security. Because of different applied environments, there are different special signature schemes, such as group signature, blind signature, proxy signature, threshold signature, ring signature, etc. Among them, ring signature, which resolves the problem of completely anonymity to signer, has been widely used. In the information era, when the study of ring signature focuses on the application, the efficiency turns to be the key point.Firstly, the basic knowledge of cryptography is introduced, including ring, finite field, and quadratic residue problem, one-way function, hashing function, random oracle model and signature. Then new achievements of cryptography in recent years are depicted in detail. They are the conic curve over the ring Z_n and XTR cryptosystem.Secondly, the achievements in the field of ring signature and its applications are surveyed. The concept, sorts and applications of ring signature are studied. Then, some problems and open problem are concluded.Thirdly, the properties of conic curve over ring Z_n (CCC) are used to construct secure and efficient ring signatures. CCC is easier to accomplish for embedding plaintext, computing element order and points in curves, and speeding up the inverse operation, so it is fit for constructing cryptographical protocols. New blind ring signature and linkable ring signature based on XTR are proposed. Then they are used to construct e-cash protocol which can protect the anonymity of the bank and trace double spenders.Finally, the work of the thesis is concluded.