Security Analysis Of Hash Function MD5

Cryptographic hash functions play a key role in Information Security and Cryptography. In recent years new collision attack on hash functions made known to the world. A series of hash functions such as MD4, MD5, RIPMD, HAVAL and SHA-0 have been attacked by Wang et al. using Integer Modular Subtraction Differential Analysis Method. The complexity of all the attacking algorithms doesn't exceed 2 40compression-function computations and examples of the collision can be found on a personal computer. In this thesis, we discussed our latest research results on the analysis of hash function MD5.Firstly, we discussed the derived sufficient conditions for collision differential path of MD5. At the conference EUROCRYPT 2005, Wang et al. presented the 2-block collision differential path of MD5. We found that the derived conditions for this collision differential path were not sufficient to guarantee the path to hold and that some conditions could be modified to enlarge the collision set. In order to give a true set of sufficient conditions, we investigated the properties of integer addition in binary representation to derive extra conditions through the feedback calculation. We proved that the derived extra conditions a_2,27 = 0, a_2,29 = 0, a_2,30 = 0 and a_2,31 = 0 of the first iteration are not only sufficient but also necessary conditions for the collision differential path. With these basises, we sumed up the general approach to derive sufficient condition set for collision differential path of MD5. This...