The Design And Analysis Of Incremental Hash Functions Based On Block Ciphers

Hash function plays a very important role in the area of information security. As a significant branch of cryptography, the hash function is very wide scope of application. In accordance with the way to construct a compression function, hash function is divided into two categories; they are special design hash function and block-cipher-based hash function. Merkle-Damgard method is one of the most famous iterated hash functions. Its property is that if the compression function is collision attack, then the corresponding hash function is collision attack too. However, it is vulnerable to Joux multicollision attack and herding attack. In order to resist these two attacks, researchers proposed a transformation of Merkle-Damgard method which is called 3C-Hash. But it still vulnerable to these two attacks. In this dissertation, an improved hash function which is in allusion to the defect of Merkle-Damgard method and 3C-Hash is proposed.The main works in this dissertation are as follows:(1) Studying the theoretical basis of block ciphers and hash function. Then analyzing the defect of Merkle-Damgard method and 3C-Hash. In allusion to the defect, presenting the improvement of these two iterated hash functions.(2) Researching the theoretical basis incremental hash function and analyzing the defect of it. Although incremental hash function can compute the hash value of changed message with a high speed, it has to cost certain memory space to store the hash chain value.(3) In allusion to the defect of Merkle-Damgard method and 3C-Hash, an improved incremental hash function is presented in this dissertation. Compressing and padding the blocks before inputting them into the compression functions to confuse and diffuse the message. So that the difficulty of attacker is increasing. In order to achieve the least size of hash value 160 bits, this dissertation uses two branches and at last connects them as one value.(4) The security of the improved hash function is proved by black box and weighted Knapsack Problem. And the Joux multicollision attack, herding attack, long-message second preimage attack and birthday attack are also used to analyze its security.