Research On Scrambling And Diffusion Scheme Based On Hyperchaotic Sequences For Secure Optical OFDM Systems

OFDM technology has been widely used in optical fiber communication and other fields of communication, due to its high spectrum efficiency, and it can effectively resist selective fading of frequency and time dispersion. With the development of society, a lot of information needs to be transmitted through optical network. Thus, combining OFDM technology with optical communication to construct a network with higher transmission rate, longer transmission distance and low cost is very necessary. As the participants of information transmission on the optical network are increasing, how to ensure the security of information becomes a very important task. By applying chaos technology to the secret communication area can solve this problem partly, because of the characteristic of chaos.This paper proposes three encryption schemes based on hyperchaotic sequences for secure optical OFDM systems. And the simulation experiments are completed in the Optisystem communication simulation software and Matlab software. The main works in this study are as follow:(1) Proposing a scrambling encryption scheme based on hyperchaotic sequences for secure optical OFDM systems. This algorithm has a well performance in encryption function through simulation experiment and data analysis. However, this encryption system has a major drawback:it can not resist differential attack.(2) A unidirectional diffusion encryption algorithm is proposed to overcome the shortage of the scrambling encryption algorithm. As the new algorithm uses the diffusion method, it can effectively resist differential attack. And the data analysis proves that the algorithm also has a high performance.(3) In order to improve the transmission efficiency of the optical OFDM encryption system, a bidirectional diffusion encryption scheme based on hyperchaotic system is proposed. Compared with unidirectional diffusion, there is no scrambling-diffusion process in bidirectional diffusion. And only forward diffusion and backward diffusion constitute the steps of bidirectional diffusion, therefore, it can greatly improve efficiency of the encryption system. Furthermore, the encryption effect of bidirectional diffusion is as well as that of unidirectional diffusion.The success of there simulation experiments indicates that the encryption schemes based on hyperchaotic sequences for secure optical OFDM system have some possibilities of being applied in practical optical network. And the encryption systems can ensure the information well, because of the characteristic of hyperchaos.