The Research On Theoretical Design Andanalysis Method Of Chaotic Cryptography

Information security is the important guarantee of modern internet communication, and application of cryptography effectively ensures security and integrity of the data. Due to the unique advantages on encryption, chaos becomes a hotspot in academia. Up to now, lots of encryption algorithms have been proposed, but they still have flaws.Therefore, the need of high quality cipher from high performance algorithm is urgent. Typical discrete and continuous-time chaotic systems are deeply studied in this paper. The feature and deficiency of different systems are summarized: the structures of algorithms based on discrete chaotic systems are too simple, and key spaces of them are not enough; Continuous-time chaotic systems commonly have long run courses and disrelation process. Besides, synchronization will decrease sensitivity of the systems. According to this, design schemes of stream cipher based on discrete and continuous chaos are proposed in this paper. Stream cipher based on composite discrete chaotic system flexibility selects iterated function. The composite iterated process makes plaintext naturally embedded into ciphertext, and efficiently prevents ciphertext from leaking information of plaintext. Generalized synchronization is used in stream cipher to solve the problem of sensitivity decrease. Results show that 95% of sequences have passed randomness test, and largest error to ideal run courses is 0.6%. 99.24% of ciphertexts have excellent uniform distribution. Stream cipher based on orbit perturbation provides a perturbation function for continuous-time chaos. It greatly improves randomness and run courses of the systems. Results show that disrelation process and departure time of the sequences decline to 5.4%-13%. The largest error to ideal run courses is only 0.45%. The peak of correlation declines to 12%. Moreover, the key space is enlarged to some extent due to the time-varying parameters. At last, a software system is designed to analyze chaotic systems and sequence and algorithms based on them. It integrates a lot if emulation functions to different chaotic systems, and will make work more efficient. The conclusion is that this paper makes progress on chaotic stream cipher which needs high quality, and increase the feasibility of chaotic stream cipher in information security.