Analysis And Research On Forward-secure Digital Signature Technology

With the rapid development of computer and network technologies, information security has become one of the most important problems in modern information society. As the kernel technique of information security, the modern cryptography has received considerable attention all over the world. Digital signature, which can provide authentication, integrity and non-repudiation, is what the modern cryptography mainly studies with. Meanwhile, it is also the key techniques of E-commerce and E-governance with security. The digital signature will become more and more popular when the e-signature law is put in practice.Because of a variety of application backgrounds in e-commerce, researches on the digital signatures with different characteristics have more practical significance. Forward-secure digital signature is one of the main measures in Information Security Risk Control. Thus, it has been becoming a hotspot of cryptography researches, as well as an important research content of digital signature at present. The essential feature of forward security is the security and risk control of the digital signature, so forward-secure digital signature can effectively reduce the loss that arises from the secret keys exposure.This dissertation systematically discusses the theory and method of digital signature and its applications. The research focuses on the security analysis and the construction of forward-secure signature scheme and designing new forward-secure blind signature schemes through combining forward security with the fundamental ideas of blind signature. Three principal achievements having obtained in this dissertation are as follows:1. Here, we point out a class of forward-secure digital signature schemes based on n-th Root Module m hard problem having security omission and sum up the essential causation of an adversary forging the valid signatures successfully. In addition, the two signature schemes of the class schemes are improved. Based on the hard problem of digital signature scheme, two new signature schemes are proposed by using the current secret key or the information about the current secret key to sign the message. The two improved schemes not only have the features of forward-secure and resisting forging attack, but also improve the signing speed effectively. The improved methods are equally applicable to such other digital signature schemes based on n-th Root Module m hard problem. And these methods have certain guiding significance on further designing some forward-secure special signature scheme having practical application values.2. We design a forward-secure weak blind signature scheme and a forward-secure strong blind signature scheme based on ElGamal. By the proposal of a new conception named correlative-factor assisting the secret key in evolving, the two proposed schemes conceal the current secret key and convert it into the stochastic actual secret key, which is used to sign the current message. This method establishes the connection between the signature for different periods and the secret key of the same period, which ensures that the secret key and the entire scheme both have forward security. The correlative-factor, as an important component of the signature, participates in the verification phase. The security of the two proposed schemes is based on the discrete logarithm hard problem in the finite field. The two new schemes increase the forward security and limit the effective time of the blind signature compared with the previous blind signatures, both of which make the schemes not only have weak blindness or strong blindness, but also have strong unforgeability.3. We present a new forward-secure strong blind signature scheme based on elliptic curve cryptosystem by using the bilinear property of Weil Pairing defined on elliptic curves. The security of the new scheme is based on the assumption of difficulty in solving the non-super singular elliptic curve discrete logarithm problem over finite field which has no efficient attack method by now. The proposed scheme has the features of forward-secure, strong blindness and resisting forging attack, by which ensures the safety throuthout the lifetime of the scheme effectively on elliptic curve cryptosystem.