Research On Forward-Secure Ring Signature

Ring signature is an anonymous signature technology. The ring member signs a message in an unconditionally anonymous way in ring signature. The verifier can be convinced that the signature comes from a member of the ring, but don’t identify the actual signer. Ring signature also exists key exposure problem as a special kind of digital signature.Key exposure problem brings huge losses to digital signature. Because once the key is leaked, all signature which are generated by the key will be invalid. Forward-secure digital signature reduces the losses which are bringed by the key exposure problem effectively through the algorithm of updating key, but it can not guarantee backward security of digital signature. The idea of strong forward-secure digital signature is that the attacker can not forge the late signature even if he gets the current key.This thesis mainly focuses on the research of ring signature and forward-secure digital signature. Aiming at the problems which the current forward-secure ring signature exist, the main purpose of this thesis is that it analyszes the essential reasons of the problems and constructs more secure forward-secure ring signature schemes and strong forward-secure ring signature schemes. The main work is as follows:(1) We analyzed the forward-secure ring signature which was proposed by Wang Ling-ling et al.. We found that the scheme existed security omission because of lacking forward security. Aiming at the problem,we summed up its essential and gave an forward-secure ring signature. In the new scheme, the defect that the original scheme signed with constand was overcome by changing the algorithm of ring signature. The improved algorithm combined the updating private key and ring signature really. We analyzed security and efficiency of the new shceme. The analysis shows the new scheme has correctness, forward security,unconditional anonymity, verifiability and can resist forging attack., as well as higher signing efficiency.(2) Based on the new forward-secure ring signature, we proposed an strong forward-secure ring signature by means of updating two private keys. In the scheme, one updating private key was used to ensure the forward security of ring signature. The other was use to ensure the backward security of ring signature. So the scheme has strong forward security. At last, the analysis shows that the new scheme has correctness, strong forward security,unconditional anonymity, verifiability and can resist forging attack.