Former To Secure Signature Scheme

To achieve transaction security,digital signature is one of the core technology.Its implementation is based on encryption technology.Key loss is fatal to the cryptosystem,the whole system will no longer safe,loss can not be estimated.Then,in 1997 Anderson proposed the forward-secure digital signature.This idea change the original model of common digital signature,advance the concepion "Survive Cycle" to the public key,cut the cycle into kinds of periods. Public key remain unchanged in the entire "Survive Cycle",but private key keep changing in each period.The change is to be one-way.Even if the key lost,as the attacker can not fabricate the signature before,the loss reduced significantly.On the basis of previous studies,I do the following work in this paper:PartⅠ,analysis the relationship between the encryption,signature and the security.Give five deformed ElGamal signature scheme,carry out the analysis and the comparison to the efficiency and the security.Introduces Rabin Probabilistic Cerebration and put this cerebration to ElGamal signature scheme, compare with the original scheme,the security enhance large.PartⅡ,This paper analyses the forward-secure signature,indicates that forward-secure ElGamal signature does not possess forward-security actually. And then presents a new forward-secure signature scheme,as there needs the time period's information whether signing or verifying,even if the attacker obtains the secret key of a certain time period,he can not fabricate a effective signatures of any time before.And the security and the efficiency improved significantly.PartⅢ,Describes the appliance of forward-secure sheme in bland and proxy signature.Propose a new deformed forward-secure bland signature and a new deformed forward-secure proxy signature.And carries out the analysis and the comparison to the efficiency and the security.