A Double-length Hash Function Based On AES

Since 1970s, the Internet has been increasingly developed and widely used for its conveniency and efficiency. But for the potential weakness of the TCP/IP, the data on it are vulnerable to various attacks. Along with the increasing development of it, security has become a tremendously important issue to deal with.One essential aspect for secure communications is cryptography. Being an important part of it, hash functions are widely used in computer and network security. Butt several attacks have showed that the most popular MD design principle for hash function couldn't be securely used in practice any more.Firstly, we sum up the main attack techniques on hash functions and show the basic attack method taking SHA as an example. Our study concentrates on the birthday attack, the length extension attack, the differential analysis, the message modification method, the multi-collision attack, the fixed point attack and the neutral bit attak.Then we construct a secure double-length hash function based on Rijndael with a collision resistance ofΩ(2228), which can take any message in practical as the input and output a 512-bit hash value as the fingerprint of it. The additional operation to pad 0 or 1 to the beginning of the message blocks makes the length extension attack not to be work. The method to construct the encryption block based on AES makes the algorithm stay safe under the differential cryptanalysis. The secure domain extension method makes it resist on the multi-collision attack. And we choose the secure PGV so as to avoid the fixed-point attack.