Ordinary Digital Signature Algorithm Research And Improvement

Digital signature is a very important method in authentication. As an aspect of the digital signature, general digital signature has been taken into much account due to its wide usage. Most of the previous general digital signature algorithms, however, are vulnerable to the so-called homostasis and active attacks. Therefore, it is very necessary to improve the exiting general digital signature algorithms and even design some new securer and more efficient ones. In this paper our work aiming to such a challenge is as fall o ws: (1) Introduction to the characteristics and classfication of digital signature, digital signature schemes based on a private-key system or public-key system, and the core concepts of public-key system. (2) Evaluation of four existing typical general digital signature schemes, including RSA, ELGamal, DSS/DSA, LUC. It is shown that most of them are vulnerable to the so-called homostasis and active attacks. (3) Discussion of the security and structure of hash function. Its construction method, choice of one-way function and design theory is also involved. (4) Presentation of a new one-way hash algorithm, MSHA, using four new hash round functions. Compared with the existing and widely used SHA-l, which is regarded as the securest hash algorithm presently, MSHA has a better safety and comparable speed. (5) Proposition of a new ELGamal-like digital signature algorithm, ELDSA, by use of a self-certified public key. It has the advantage that the authentication of a public key can be accomplished during the verification of the signature. In the same time it is characteristic of less calculation and storage. The one-way hash functions, factorization and assumption of discrete logarithm ensure the security of ELDSA. (6) Analysis of the security and time complexity of the new algorithms. It is demonstrated that they are secure enough with less time complexity.