Research On Some Block Chaotic Cryptographic Algorithms

With the fast development of Information Technology, information becomes most important thing of our lives. We would focus the value of the information, meanwhile we care security of our important information in order to avoid being stolen by the hackers. Many scholars are doing their research on the cryptography, no matter which methods they use, the speed and the security are the first being considered.Instability to the initial value make the dynamic chaotic system can be used in cryptography. The good properties of the dynamic chaotic system have potential on the field of cryptography application. But the real chaotic system is based on floating-point domain, we only can implement the digital chaotic system with the help of computer technology. Chaotic system cannot be directly used like the theories that we can obtain all excellent properties like infinity cycle etc. This paper mainly concerns the security of chaotic block cryptographic algorithms and proposed two novel cryptosystem. Then the simulation and analysis has verified the algorithm's excellent security performance. Specifically as follows:(1) Use cryptanalysis method to attack a novel typical chaotic block encryption algorithm. Then I found a flaw that this algorithm cannot resist the chosen-ciphertext attack. It will greatly reduce the security of the algorithm. And this flaw exists in lots of block encryption algorithm. I propose a method to remedy the flaw that not only retain the features of original algorithm, but also increase the security of the algorithm.(2) A new non-symmetric chaotic block encryption algorithm. This algorithm mixes with chebyshev polynomials and logistic map. Based on the semi-group property of the chebyshev polynomials, I propose a public key algorithm, and use traditional chaotic block encryption method to enhance the encryption speed. In order to avoid losing accuracy, I extend the chebyshev polynomials from floating-point to finite field.(3) A novel chaotic block encryption using dual S-box. This algorithm constructs two S-box dynamical. One uses for substituting the plaintext, and the other uses for confusing the sequence of the plaintext. The two S-box enhance the security of the chaotic block encryption.