Study On Chaotic Encryption Technology Based On Erbium-doped Fiber Lasers

With the fast development of modern information technology and the integration of global information network, information system has become a pivotal infrastructure that is depended by politics, economy, education and individual life etc. As the information network bring great convenience to the whole world, the information system security has become the focus of the whole society, the information security has become a very important matter which relates to the national political stability and social harmony and the orderly development of economy. In recent years, some more advanced and more promising theories and methods are introduced the field of information security. The chaos theory possesses several specific characteristics such as good pseudo random properties, rail unpredictability, the extreme sensitivity to initial conditions and the control parameters, some properties match to cryptography. Therefore the chaos theory which locates the across of the two fields of international nonlinear science and information science has become a hot research topic of secure communication and information encryption technology.Since the British mathematician Matthews put forward the thought based on chaotic encryption in 1989, chaotic cryptography has experienced the development process for 20 years. During this period, new chaos systems and new encryption schemes applied to data encryption, image watermark encryption, video encryption, encryption and other fields incessantly. The generation and application of chaos phenomena in optical systems has become an important part of the research on chaos system in resent years, However most of the study focused on the field of chaos synchronization secret communication. The study of this dissertation introduces the optical chaos system to the chaotic encryption field for the first time. The dissertation studies the applications of digital image encryption algorithm and digital watermark algorithm by utilizing the chaotic sequences that generated by the erbium-doped fiber laser chaotic system. Meanwhile, it also analyzes and discusses the application of chaos theory in the database encryption application. In this dissertation I proposed and studied the feasibility of improving the database core encryption algorithm by using the chaotic sequences which generated by the erbium-doped fiber laser. The whole dissertation can be divided into five parts:The first part is the literature review of the whole dissertation. First, based on new requirements of the encryption technology of the information security to modern cryptography, via the brief introduction of the chaos theory and optical chaos, this part puts forward the background and significance of the subject research. Then I introduce the development process of chaos from its birth to being admitted, and it plays more and more important role in various fields. The first part introduces two kinds of define methods of chaos in mathematics: the definitions of Li-York's and Devaney's, and summarizes the basic characteristics of chaotic systems according to the analysis of the chaotic concepts. Describes the analysis method of chaotic systems such as bifurcation diagram, attributor, Lyapunov exponent, the power spectral density and Kolmogorov entropy, etc. Finally, based on the introduction of information security and encryption algorithm of cryptography, I analyzed the similarities between chaos and cryptography, summarized the recent research progress and the main application methods that introduce chaotic system into the field of information security. Thus make the preparation for the research in next phase.The second part of the dissertation mainly studies on erbium-doped fiber laser chaotic sequence. Based on the introduction of the study on optical chaos, I setouts the system framework and luminescence principle of erbium-doped fiber laser, and discusses the chaotic theory and methods of erbium-doped fiber laser by analyzing the dynamic behavior and normalized equation. Then based on the study, the method that generates chaos by adding optical delay feedback to the single ring erbium-doped fiber lasers is discussed in detail, and the complicated nonlinear dynamic behavior and rich chaos characteristics of this system are proved by using the bifurcation diagram and Lyapunov exponent method. Finally, the assume that using erbium-doped fiber ring lasers with an optical delay feedback (ODF-EDFL) chaotic systems as chaos sequence generator is proposed. I put forward the concept of change rate of ODF-EDFL chaotic system to translate the real value chaotic sequences into binary chaotic sequences, and I also design a new optimization model that disturbs the mixed binary chaotic sequences by m-sequence: firstly the two binary chaotic sequences that are generated by ODF-EDFL chaotic system are mixed by XOR operator, then disturbed the mixed sequence by using m-sequence which has good random characteristics. This model improves the uniform distribution characteristic of the ODF-EDFL chaotic sequences greatly. These statistical tests (such as balance test, runs test, serial test, auto-correlation test) verified the excellent random statistical characteristics of the mixed chaotic binary sequence. This mixed binary chaotic sequence set up better foundation for the design of the following encryption algorithm based on chaotic sequence.The third part of the dissertation mainly studies on the encryption algorithms which utilizes single ring erbium-doped fiber laser mixed binary chaotic sequence to design digital image. This part first introduces the basic principles and methods of image encryption, analyzes the recent research status and achievements of digital image encryption, and the principle of space scrambling of Arnold transformation and magic cube transform are discussed concretely. Then a new image encryption scheme is proposed via analyzing those encryption algorithms: Generates the value chaotic pseudo-random sequences and the mixed binary chaotic sequence by applying ODF-EDFL chaotic system, meanwhile, changes the pixel grey value of the image by using the binary sequence and to confuse the pixel position by the two real-value chaotic sequences by using a novel method of space scrambling to digital images named pixels-minesweeper-scrambling (PMS). Finally the excellent encryption and decryption of this algorithm is proved by the results of simulation and security analyzing. This encryption algorithm has very strong sensitivity and better statistical characteristics. It even has more outstanding performance in the condition of the anti-interference and resists malicious attacks.The fourth part of the dissertation mainly studies on the design of color image watermarking algorithms based on single ring erbium-doped fiber laser mixed binary chaotic sequence. Firstly this paper introduces the study background and significance of digital watermarking, expounds the basic principle, characteristic and classification of digital watermarking technology. Then the conception and classification of wavelet transform are discussed, this part emphatically analyzed the definition of discrete wavelet transform (DWT) and analyzed the advantage of using Mallat algorithm technique to decompose the digital images in the field of design digital image watermarking algorithm. Finally, the erbium-doped fiber laser chaotic system is applied to image watermarking research field for the first time, which based on the analysis of chaotic systems in application of digital watermarking. Design and implement a novel color image watermarking algorithm that using ODF-EDFL chaotic sequences to encrypt watermark information, this novel algorithm can also embed and extract watermark by using the characteristics of human visual sense complements and DWT technology. It can improve the effect of watermark image encryption results and ability to resistance crack after applying the optimized ODF-EDFL mixed binary chaotic sequences to encrypt watermarks; The design of embedding watermark information into the green components in color image improved the ability of this algorithm on resistance against JPEG lossy compression. And the embedding algorithm based on DWT enhances the robustness of against other attacks. The computer simulation experiment and attack ability test proved the outstanding visual effect and the ability to resist attacks of this algorithm.The fifth part of the dissertation mainly discusses the application of chaos theory and technology in customs database encryption. First the necessity and meaning of encrypting the customs database which deposit important sensitive data on the current situation of information security are discussed in this paper. Then the main technology of database encryption has been divided and reviewed based on the analysis of database security requirements and target. Finally, according to the front part study in the chaotic encryption technology field, the conception and discussion on the application of the customs database encryption system by using chaotic technique is put forward. Furthermore, the encryption algorithm such as AES, RSA etc which play a key role in database encryption are improved by using ODF-EDFL mixed chaotic sequences, and the simulation results show the feasibility and availability of improve the ability to crack which can expand key space of encryption algorithm.The research and numerical simulation experiment of chaos encryption technology that based on erbium-doped fiber laser system in this dissertation introduce erbium-doped fiber laser chaotic system into chaos encryption fields, and provide some theoretical and experimental basis for the application in optical chaotic encryption and confidential communications field, and even made some exploration and achievement.