| With the advantages of wide spectrum,fast transmission speed and complex dynamic characteristics,optical chaotic signals have attracted a lot of attention in the fields of secure communication,image encryption and other applications,recently.In the field of secure communication,optical chaotic signals are used for masking original message;In the field of image encryption,optical chaotic system generally acts as a pseudorandom sequence generator.There are two keys to traditional chaos secure communication system: One is to establish reliable chaos synchronization between two ends.Then by introducing some external disturbances,such as:changing the bias current of laser,the information is modulated to the chaos carrier,so as to achieve the purpose of high-speed communication.The other is the complexity of optical chaotic signal.If the system has low complexity,then it is easy to be reconstructed by neural network.The complexity of chaotic signals is closely related to the dynamic characteristics of chaotic systems.Therefore,it is necessary to adjust parameters to optimize the dynamic state of the chaotic system,and generate chaotic signals with high-dimensional and high-complexity to reduce the possibility of system reconstruction.Chaotic secure communication system based on chaotic synchronization has high communication quality and fast transmission speed,and is suitable for large-scale data transmission and communication,such as image information transmission.However,due to the influence of manufacturing process and noises,the quality of synchronization can be severely damaged.Therefore,it is necessary to find a way to accomplish chaotic communication without chaos synchronization.By focusing on the current hot issues such as data security transmission and image encryption,aiming at the characteristics of secure communication and image encryption applications,and combining the research basis at home and abroad,an optical chaos asynchronous communication scheme and a color image encryption scheme based on optical chaos synchronization and elliptic curve cryptography are proposed.The main results are as follows:(1)An asynchronous chaotic secure communication system using a new modulation on optical chaos combining with linear block code is proposed.At the transmitter end,chaotic optical signals are generated by a semiconductor laser with electro-optical phase feedback.The largest lyapunov exponent(LLE),permutation entropy(PE)and Lempel-Ziv complexity(LZC)of the output optical signal are calculated to determine whether the system enters chaotic state and evaluate the complexity of the output chaotic signal.Then the parameters of the optical chaos system can be optimized.After the optical signal is converting to electric signal by phonton detector,the sum of the absolute values at adjacent three sampling moments are calculated.The interval between maximun and minimum values are divided into eight different segments.Each segments encodes the chaotic signals of the three adjacent sampling times with different positive and negative coding method.The thresholds of the segments are used as the external key for generating a new chaotic sequence.Linear block code is used for channel coding,and the chaotic signal with information is transmitted to the receiver through single-mode fiber and dispersion compensation fiber.At the receiver,eight different demodulators are designed for eight different segements.Moreover,numerical simulation proves that our scheme can achieve secure communication without chaos synchronization and the bit error ratio performance is improved comparing to some related works.(2)A color image encryption model based on optical chaos synchronization and elliptic curve cryptography is proposed.In this scheme,the bias current of master laser(ML)is controlled by the hash value of plain image.Master laser drives three twin slave laser pairs(TSLPs)into chaotic state.Each TLSP uses phase-modulated optical feedback to generate chaotic signal.Two of the TSLPs are used to generate random sequences which is used for scrambling,diffusion and their reverse process.The other TSLP is used to generate chaos carrier to transmit encrypted message.In the design of scrambling method,a three-layer scrambling method combining spiral matrix scrambling,index scrambling and cross-channel scrambling is proposed.In the design of diffusion methods,bit XOR diffusion method is used.In order to further improve the effectiveness of encryption,every thirty-two pixel values that have been scrambled and diffused are combined into a large number,and then the EC-El Gamal algorithm is used for secondary encryption.In addition,numerical simulation show that:first,the optical chaos synchronization system can generate high-dimensional chaotic signals with high complexity by adjusting injection strength and feedback strength;Secondly,the encryption system can effectively resist attacks including histogram analysis,information entropy analysis,differential attack,noise attack and other classic attack forms;Thirdly,by monitoring the synchronization error of the SL at the transmitter and receiver,the original information can be recovered successfully.Finally,eye diagram is plot,which shows that the communication system has high communication quality.In summary,this study focuses on optical chaos and introduces several ways of generating optical chaos.The chaos dynamics of electro-optical phase feedback system and phase modulated optical feedback system are mainly studied.By adjusting the parameters of the dynamic system,suitable parameters are found,which can generate high-complexity optical chaotic signals.Two applications of optical chaos are proposed by using high-complexity optical chaos signals.which are improved and innovated while drawing on existing achievements,and have a positive role in promoting the application and development of optical chaos and its dynamics.These two applications based on optical chaotic proposed in this paper not only learn from the existing achievements,but also conduct some innovation and improvement,which has a positive effect on the development of optical chaos,chaos dynamics and their applications. |
