The Research And Application Of Encryption Algorithm Based On Chaos

With the advent of the mobile Internet era, the smart phone, a mobile terminal with the largest number of subscribers, brings people a lot of convenience, however, at the same time some data security problems have arised, encrypting the data is the most common way among all sorts of solutions in data security.As a new data encryption standard, AES(Advanced Encryption Standard) algorithm has been favored in all areas of society. But due to the defect of the key expansion algorithm in AES algorithm, it is easily threatened by password attack. The chaotic system with pseudorandom property and high complexity can make up that deficiency. Therefore, in this thesis, combining with chaos theory and AES algorithm, an improved AES algorithm based on variable parameter chaotic sequence is proposed, and an encryption or decryption android software with the improved AES algorithm based on variable parameter chaotic sequence is designed. The main efforts are as follows:1) This thesis analyzes the shortage of the key expansion algorithm in AES algorithm: it has a great correlation between the round keys in AES algorithm, the front and back round keys can be deduced from each other.2) Based on the Chebyshev chaotic map, Logistic chaotic map and Cubic chaotic map, a low dimensional multi chaotic system with variable parameter is designed. The sequences generated by a low dimensional multi chaotic system with variable parameter are verified from the aspects of the period, 0-1 balance and correlation. It proves that the low dimensional multi chaotic system with variable parameter is more excellent than the Logistic chaotic map.3) The design and performance analysis of the improved AES algorithm based on variable parameter chaotic sequence. Firstly the plaintext data and the sequences generated by the low dimensional multi chaotic system with variable parameter are processed by XOR; and then adopt the improved AES algorithm in which the sequences generated by the low dimensional multi chaotic system with variable parameter are deeded as round keys to encrypt the data, each round key is randomly generated without any linkage; Finally the positions of elements in ciphertext are adjusted to enhance the safety of the algorithm. The improved AES algorithm based on variable parameter chaotic sequence and standard AES algorithm are compared by MATLAB simulation software from three aspects: security, encryption efficiency and cost. The conclusion is that the improved AES algorithm based on variable parameter chaotic sequence has higher security without too much impact on the encryption efficiency and cost.4) A software to encrypt or decrypt the image and audio on the android platform is designed according to the improved AES algorithm based on variable parameter chaotic sequence. The test on the app software shows it achieves the expected requirements of the encryption and decryption.