Security Analysis And Enhancement Of Time Delayed Chaotic Secure Communication

Information security has become more and more important in the information society,and the existing secure communication methods are facing challenges.As the lowest layer in the Open System Interconnection(OSI)model,Physical Layer Security(PLS)has the characteristics of less resource consumption,less delay and higher security.It is independent of the upper structure of the OSI model and has good compatibility with the existing communication systems.The research of PLS in recent years has attracted considerable attention.Chaotic secure communication has the characteristics of low cost,anti-noise and high security.It can be integrated with the upper layer security mechanism to establish a new cross-layer security hierarchy.Chaotic secure communication will have broad application prospects in future unmanned system communication with open channel.PLS is no longer dependent on the computational complexity of the encryption algorithm.Instead,the security is guaranteed by the complexity of physical processes.The unique dynamic characteristics of chaotic system,such as the sensitivity dependence on initial value and parameters,stochastic bahaviour,provide theoretical guarantee for the security of communication.In real world applications,a secured chaotic source is the core component of a secure system.It is also the fundamental base of the whole security hierarchy.A time delayed chaotic system has a simple structure and a hyperchaotic attractor in an infinite-dimensional phase space,which provides a higher level of security in chaotic secure communications.Focusing on the topics of time delayed chaotic systems,we have conducted some research works.The detailed contents are as follows:From the attacker’s perspective,we have discussed the problem of parameter estimation under the situation that the chaotic signals are only transmitted at discrete instants.For chaotic systems without time delay,parameter estimation is hard to perform when continuous time chaotic signals are unavailable.Based on impulsive differential equation theory,sampling control and adaptive control methods,we proposed a new parameters estimation method.The results show that even if the signals are sent at discrete instants to reduce the leakage of system information,there are still security risks in chaotic systems without time delay.The unknown system parameters can be successfully estimated only by using the discrete sampled data of the output signals from the chaotic sources.The dynamical characteristic of time delayed chaotic systems are much more complicated.The generated chaotic signals have better randomness and unpredictability,which means these systems have a stronger attack-resisting capability.Therefore,we have discussed the parameters estimation of time delayed chaotic sources.For this problem,compared with the existing literature,our innovation lies in taking the two issues into account simultaneously:(i)all the system parameters and the time delay signatures are unknown to the attacker;(ii)the attacker only sample the output signals of the chaotic source at discrete instants.Based on impulsive time delayed differential equation theory,sampling control and adaptive control methods,we have proposed a new paramters estimation method.The results show that even if the signals are sent at discrete instants to reduce the leakage of system information,the introduction of time delay cannot guantee the security of chaotic secure communication system.The unknown system parameters and the the time delay signatures can still be effectively estimated only by using the discrete sampled data of the output signals from the chaotic sources.From the perspective of system designer,we have proposed an enhanced construction strategy for time delayed chaotic sources based on the intermittent time delay modulation(ITDM)method.The effectiveness of this strategy has been verified by constructing a time delayed hyperchaotic Chen system with ITDM.Moreover,we have proposed a security enhanced Ikeda type chaotic system with electro-optical time delayed feedback.Optical switching technology is adopted to establish the ITDM.The detailed conditions for setting the proper parameters are studied by means of numerical simulation.