Study On Chaotic Dynamic Characteristics Of A Semiconductor Ring Laser And Its Application In Image Encryption

With the rapid development of computer technology,image encryption and decryption technology has been widely used in people's daily life.The security of the traditional chaotic image encryption and decryption system depends on the performance of the chaotic system,and the low-dimensional chaotic system is easy to be attacked by common image attacks techniques,such as chosen-plaintext attack,known-plaintext attack.However,the high dimensional chaotic system has some disadvantages such as high implementation cost and low running rate,which can't meet the security requirements of modern communication system for high speed and high bandwidth.Chaotic systems based on semiconductor lasers have been widely studied because of their high speed and high bandwidth.As a novel semiconductor device,semiconductor ring laser has many advantages of semiconductor laser,and it is easy to integrate into the chip.Because of its ring cavity structure,it can exist two kinds of light propagation mode at the same time,and can be used for parallel data processing.Therefore,the chaotic system of semiconductor ring laser is applied to the image encryption and decryption system to improve the security and efficiency of encryption and decryption,and the feasibility of the design is verified by numerical simulation.The main research contents are as follows:1.The mutually-coupled semiconductor ring laser chaotic system is proposed.The model structure and rate equation are given.By extracting the peak value of autocorrelation function,the effects of injection intensity,frequency detuning and linewidth enhancement factor on the time delay characteristics are analyzed.A method for obtaining four chaotic signals with high speed and high bandwidth at the same time in the larger dynamic tunable range of controllable parameters is presented.2.A design scheme of true random number generator based on chaotic synchronization system of semiconductor ring laser is presented.The randomness of generating random number sequences is greatly improved by effectively combining delayed XOR,down sampling and buffer mechanism.The synchronous true random number is generated based on the high quality chaos synchronization between master and slave laser.The synchronous true random bit sequence with real time rate of 4Gb/s is obtained in the simulation,and all of them pass the NIST test.3.It is the first time that the true random number sequence is used in the image encryption and decryption system,which is used as the key to encrypt the image,and makes the image encryption and decryption algorithm have the security of “one-time-pad”.In the simulation,the key related to plaintext is used to generate the initial values and parameters of the chaotic system in the preprocessing stage by using the SHA-256 hash algorithm.The nonlinear bit scrambling operation is used to reduce the spatial distribution of the plaintext image and the local correlation between pixels.The confusion and diffusion stages are realized by simple shift and XOR operations respectively.Finally,the security and computational complexity of the proposed image encryption algorithm are analyzed to prove the feasibility of the scheme.