Design And Implementation Of The Single-Block Hash Function Based On S-Box

Hash function is a message digest algorithm, which characteristic is irreversible, and has been commonly used to verify message integrity in data transmission, check errors, quick search and so on. Many websites save the hash value of user account and password to avoid the system administrator eavesdropping user information. Hash function also has great significant in digital certificate, by hashing vitally important information in the certificate content to protect certificate integrity and enhance the efificiency for verifying certificate legitimacy. But in pratical application, traditional hash function to hash a short message would result in a waste of efficiency, and single-block hash function(SBH) should be chosen to deal with short message. But there are security problems in single-block hash function since the message is too short to resist attack, and the original single-block hash function didn’t provide solutions to solve it.In this dissertation, we designed a more security single-block hash function, that is, secure single-block hash function(SSBH). There are two versions:one is secure single-block hash function with a key (SSBHKEY) and another is without any key (SSBH). The main structure of new single-block hash functions is similar to the Korean Encryption Standard, SEED, which is a block cipher algorithm. In order to make SEED unidirectional, we modified the initialization cache section of SEED and its core component, function F(including S-box). In the initialization stage, we filled the short message with particular bit string and only took in the data less than 128-bit. We made three registers available for function F, and changed the operation route into three lines, and added MD5 algorithm into non-linear functin. This dissertation finally implemented a back-end password authentication encryption system based on new keyed hash function, it can effectively protect the security of server back-end data. Meanwhile, we implemented a hash chain algorithm, which is widely used in certification.This dissertation has designed two experiments:algorithm efficiency and avalanche effect. There are algorithm efficiency comparisons among two new single-block hash functions, SBH, MD5 and SHA1. The experimental result shows that two new single-block hash functions at least improve 20% on efficiency. The experiment of avalanche effect is to observe the algorithm confusion, compared with MD5 algorithm and old single-block hash function, two new single-block hash functions have better avalanche effect, the bad point dropped about 1%. Through the above two experiments we can conclude that the two new single-block hash function are improved on algorithm efficiency and security.