The Research On Digital Image Encryption Based On Chotic Theory

The importance of information is rising along with the rapid development of computer technology and network technology. The information security and confidentiality of network becomes more significant and prominent, to be the key problem of the information-based society. Digital image exists as a special form of digital information. How to effectively ensure the confidentiality, integrity, availability, controllability and non-repudiation of digital information is the major study direction of information security technology.Chaos is a pseudo-random process of certainty in the nonlinear dynamic system, which has some characteristics such as aperiodic, ergodicity, pseudo-randomness and the sensitivity to the initial value. It has a lot of resemblance with encryption system. The current research on secure communication, information encryption and occultation, that based on chaotic theory, is one of the hot spots studies in the cross field of nonlinear science and information science.This thesis focuses on the information security of digital image and puts emphasis on the method of digital image encryption. The ground work and achievement as below:1.Based on the discussion and analysis of basic theory of cryptography and chaotic system, it focus on the study of connections between cryptography and chaotic system and the method of configuring chaotic group code.2.It analyses the chaotic shift mapping characteristic with definition on (0,1) and draw the chaotic sequence into image encryption algorithm. In the view of above, it proposes a digital image encryption based on chaotic shift mapping, which is inspected and verified to be secure.3.Aiming at the down-turn of chaotic capability caused by the digitization of chaotic system, it creates a chaotic random number generator based on the theories of Logistic mapping, Piecewise Linear Chaotic Mapping (PLCM) and shift mapping defined on (0,1), with a better randomicity and longer cycle under finite precision. It further proposes a group image encryption algorithm based on this chaotic random number generator, which has better robustness and anti-immune attack capability. Its stronger robust characteristic makes sure that the encryption image could be recovered preferably after partial damage or deficiency.4.Combined cipherblck chaining (CBC) with chaotic system, it designs an adaptive digital image encryption method. This algorithm uses the carrying image information to implement self-adapting encryption process, and meanwhile, overcomes the effect of cyclist caused by chaotic system digitizing to image encryption system. It is fast valid, secure, non-periodic, and sensitive to initial key.5.It analyses the multiplication of chaotic system and creates a new L-T multiplication chaotic system based on Logistic and Tent map. Proposed chaotic variable weight enumerative based on variable weight enumerative and chaotic system. Combined this enumerative with L-T multiplication chaotic system, it further proposes a multiplication chaotic dynamic GF ( 28) field variable weight enumerative random number generator. The sequence generated by this random number generator overcomes the disadvantage that other chaotic encryption sequence generated by simple map like Logistic and Tent is unsatisfactory at safety performance. Then based on this random number generator it designs a new image encryption which has better robustness and the encryption image could be recovered preferably after partial damage or deficiency. It is also sensitive to initial key.