Research Of Forward-Secure Digital Signature Based On Discrete Logarithms

Digital signature is an important research sub-field of information security, which can ensure the reality, integrality and non-repudiation of message. Ordinary digital signature has a disadvantage: once the secret key is stolen, attacker can forge signature. To solve the problem, in 1997, Anderson proposed the notion of forward-secure digital signature: the exposure of the current secret key doesn't undermine the validity of past signatures.On the base of previous work, this paper presents a detailed illustration of the features of the forward-secure signature and two new forward-secure signature schemes based on the discrete logarithms. Scheme one is a confirmer signature, scheme two is a "self-verifying" signature. In this paper the concept of timemark is adopted, by which the secret key of our forward-secure signature can not only make a bounded evolution but also make a unbounded evolution. A new method of the secret key evolution is proposed, which divides the evolution function into two parts—the secondary evolution function and the master evolution function. The secondary evolution function can achieve the one-way evolution of secret key by means of any one-way function, and the master evolution function makes the unlimited evolution of secret key and signature based on the discrete logarithms. With the method, we can base forward-secure signature on any discrete logarithm signature schemes. Our schemes are based on the EIGamal. Compared with the EIGamal, our schemes just add little computation in verifying. Compared with the previous schemes, our schemes have some good qualities: the secret key evolution is limitless, the public key hasn't the restriction of valid period, the public key and the secret key are shorter and don't grow with the evolution times of the secret key.In the end the model system of forward-secure signature based on the discrete logarithms is achieved. The experiment indicates that: the secret key evolution, the signing and the verifying have better efficiency.