Analysis And Research Of SHA-0 Collision Attack

As an important part in cryptography, Hash functions play a fundamental role in modem society,for example in their use for data integrity,message authentication,digital signature scheme,distribution scheme,key exchange scheme,etc. So people attach more and more importance on the hash functions'security.The hash function SHA-0 was issued in 1993 as a federal standard by NIST. A revised version called SHA-1 was later issued in 1995 as a replacement for SHA-0. The only difference between the two hash functions is in the message expansion. SHA-1 is widely applied in kinds of encryption scheme, it is important to do research on the security of SHA-0 and SHA-1.Professor Xiaoyun Wang developed powerful techniques for analyzing currently popular hash functions in [14][15][16]. They were called modular differential attack and message modification. So the cryptanalysis of hash functions is hot in the cryptography world. Many papers are published recently. Some of them are talking about how to use modular differential and message modification technique to attack other hash functions,and the others focus on how to optimize the differential path and the search algorithm proposed in[14][15][16].The paper analysizes the local collision, near collision, mutil-block collision and modular subtraction difference technique,all of which are essential part for SHA-0 collision attack. Then effects and conditions for all these technique in collision attack are presented.In the paper, based on the differential path of [15], we discuss how to select the message differential , how to use message modification method and how to get the conditions of linear characterist, the work partially discover the underlying reasons for the selection of the path. Improved program is implemented to find collisions. We also analyze the complexity of collision attach affected by the selection of differential path , the message modification method and the early stopping technique. All the work provides efficient complement for the research of SHA-0 collision attack.