Proxy Signature And Its Former Security

Digital signature technology is of great importance in the network information security techniques and plays an important role in electronic commerce.Proxy signature provides methods to right commission in the electronic information society.Because of its spreading applied vista in electronic cash,electronic stocks,mobile agent and substitute product of electronic commerce,proxy signature was given extensive attention after proposed.Proxy signature,same as digital signature,its security depends on two aspects: anti-attack ability of proxy signature scheme and safety of the signature key.According to the Kerckhoff hypothesis,cryptosystem is always open,so the security of proxy signature is determined by the security of signature secret key.Once the secret key exposes,the whole signature scheme will be not safe any longer,so how to decrease the harm brought by the key becomes a concerned problem.A new idea of solving key exposures is forward secure idea.The aim of forward secure is to reduce the loss brought by key exposures.On the basis of proxy signature and forward-security,the forward-secure proxy signature was studied in this paper,our achievements are as follows:First,the idea of forward secure and proxy signature scheme were combined together. By adding key evolution process in proxy signature scheme,we gave the forward-security to the proxy signature key,provided forward-secure proxy signature based on discrete logarithm and forward-secure proxy signature based on elliptic curve key scheme.Second,forward-secure proxy signature can guarantee the key's safety before key exposures,while it can't prevent subsequent signature by the attacker.Based on this,we put the research on strong forward-secure proxy signature.Two strong forward-secure proxy signature schemes were given:self-updating strong forward-secure proxy signature based on trapdoor information and interactive strong forward-secure proxy signature.