Analysis And Improvement Of Ring Signature

With the steady progress of computer technology and the fast development of communication technologies, we have already stepped into the internet age. As we rely our lives more and more on the Internet, the information security issue begins to emerge. It becomes vitally important for us to build effective precautions to adapt the development of the information age, especially when facing novel Internet products like electronic banks, electronic government administration, and e-commerce. The digital signature approach, which is an essential component of information security technologies, could efficaciously solve many problems such as identity verification, data integrity and non repudiation characteristics, and thus has become a hot research topic in the information security field.When compared to group signature, ring signature is a kind of simplified group-like signature which does not need the group construction procedure (i.e., unnecessary for mutual verification between group members), and group manager (i.e., status equality between group members). The spontaneity and unconditional anonymity features achieved by group signature have established its wide application prospect in areas like e-election, e-commerce, electronic currency systems, cipher code distribution and multi-party security computing. The major contributions and conclusions of this work includes the following:(1) elaborated the fundamental theories and knowledge involved by ring signature, presented the formal definition and security model for identity-based public key cryptography ring signature.(2) Reached the conclusion that identity-based key cryptography and certificateless public key cryptography both suffer from the excessive double peer computing issue with analyses on existing ring signature schemes. To stress this defect, we proposed our efficient ring signature scheme by effectively reducing double peer computation and exponent arithmetic. The new scheme does not do double peer computation and exponent arithmetic in the signature phase, and only need to do two double peer pair verification in the verification phase. Also, this work has conducted security proofs by using the security provable theory under the random predictive model.(3) Analyzed the security defects of the Luo scheme, pointing out that the verifiable ring signature scheme cannot defend the ring member falsification issue. By embedding a certificateless short signature algorithm into the scheme, we have successfully solved the problem that ring members might arbitrarily falsify the identity of true signer.(4) Analyzed the traceable ring signature scheme of Huang and etc and found several defects of the scheme. To stress these issues, we proposed a kind of new anonymity controllable certificateless ring signature scheme, which possesses both verifiability and traceability.(5) Constructed a more efficient ring signature scheme with shorter signature length by borrowing the wisdom of Wang and etc. who built fixed length ring signature by the exploitation of an accumulator. The new scheme effectively stresses the issue that signature length depends on the ring member count, and is proved to be unfalsifiable under the q-SDH puzzle.