Security Analysis And Application Research On Hash Function

Hash function is a one-way function. Hash is widely used in digital signature and authentication. Recently, Security study of hash function is a hot spot. In this paper, Security of hash function was studied, on this basis, based on the hash function is unidirectional, two kinds of digital signature based on hash function are proposed, cryptograph data retrieval prototype system is designed and implemented. The main contributions are as follows:Firstly, Specialty about differential transition probability of SHA-3permutation function is proved. By analyzing the permutation function Keccak-f of SHA-3, cycle shift method of three-dimensional array is proposed. According to structure of every step transform in Keccak-f; the boolean expression of the output difference is structured. By analyzing the boolean expressions of the output difference, they are proved that to the every step transform of Keccak-f, the differential transition probability about cycle shift is unchanged. On this basis, they were obtained by analyzing that the differential transition probability of the whole permutation function Keccak-f about cycle shift is unchanged when cycle shift Properties of two input difference and two corresponding output difference are same.Secondly, A improved SHA-1algorithm is designed. Based on SHA-1has serious security flaws, a improvement algorithm of SHA-1is proposed. This algorithm can effectively increase difficulties using news modify, and get good differential diffusion characteristic. Due to improved SHA-1merely changed step function, only added a addition and cycle shift, did not change the filled information and digest length, therefore easy to implement to update original hardware and software based on SHA-1. Efficiency is alike between improved SHA-1and standard SHA-1through proving and realizing.Thirdly, Two kinds of digital signature scheme based on hash are proposed. Based on unidirectionality of hash function, two kinds of digital signature are structured, one is group signature scheme based on hash function, the other is threshold signature scheme based on the hash function. Digital signature based on hash function is a new signature method, no using RSA, ECC, ElGamal etc in the process of signature, can resist the attack of quantum computing.Finally, Cryptograph data retrieval system based on hash is designed and implemented. Utilizing unidirectionality of hash function, cryptograph data retrieval scheme based on hash is proposed. On this basis, cryptograph medical record retrieval system is implemented. This system has actualized retrieval and statistic useless key. This system reduces search range according to fuzzy matching about Search Term. But person who has the key is able to look up the specific information, ensure the security of the information.