Chaotic Shift Keying Research Articles

CHAOTIC PHASE SHIFT KEYING IN DELAYED CHAOTIC ANTICONTROL SYSTEMS

Based on the delayed feedback chaotic anticontrol systems, a new chaotic phase shift keying (CPSK) scheme is proposed for secure communications in this paper. The chaotic transmitter is a linear system with nonlinear delayed feedback in which a trigonometric function cos(·) is used. Such system can exhibit rich chaotic behavior with the choice of appropriate parameters. For an M-ary communication system where M=2n, each of these M possible symbols (n-bits) is firstly mapped to 2(m-1)π/M (with m=1, 2, …, M) which is used as the phase argument for the cos(·) function in the nonlinear feedback. Two different kinds of signals can be transmitted. In the first one, an appropriate linear combination of state variables is chosen as the transmitting signal based on the observer theory. In another one, a nonlinear component in the transmitter state equation is chosen. In both schemes, only a scalar chaotic signal is transmitted through the channel. Demodulation is based on the synchronization of the transmitter and the receiver, and different decoded phases correspond to different information signals.

Real Time Secure Communications via X|X| Chaos Model

A secure digital communication system based on chaotic theory is proposed to fence off the intrusion of eavesdroppers during the transmission of signal and data. With the master-slave M-synchronization technique, the transmitter and the receiver are designed using the chaotic phase shift keying. A new discrete-time modified Chua's circuit using the xlxl nonlinearity is adopted. This methodology for the design of secure communication systems can be applied to most real time communication applications, such as Internet telephone, ecommerce transactions, and digital data transfer.

Computational verb systems: Modeling with verbs and applications

Computational verb systems are methods for developing a new systematic framework of artificial intelligence by embedding the knowledge and experiences that human experts expressed or implied with verbs into machine intelligence. Computation with words is a systematic consideration of coping with complexities. While fuzzy logic provides a computing framework of adjectives and adverbs, it does not cope with verbs. It turns out that verbs are very important to describe the dynamics of complexities for the survival of human beings. Verbs should also be very important building blocks for transferring and representing human experiences, thus very important tools for the next generation of expert system. In this paper, the applications of verbs to modeling complexity are discussed. First, the dynamics of linguistic expressions are identified as the usages of verbs. Then nonlinear and linear dynamic systems are used to model and classify verbs. Based on these models of verbs, the dynamic aspects of linguistic expressions, which associate with qualitative descriptions of human experiences, can be described quantitatively. In particular, verb models of both simple and complex dynamic systems are provided to show how to use computational verb systems. Then verb models are used to solve a real life problem in chaotic cryptanalysis. First, the author's experiences on breaking chaotic shift keying are summarized by three verbs. Then the computational models of these three verbs are found by a few training examples. This computational verb model is viewed as the learned experience of computer on breaking chaotic shift keying. Some new test data are used to test the robustness and reliability of this computational verb model.

Cryptanalyzing chaotic secure communications using return maps

In chaotic secure communications, message signals are scrambled by chaotic dynamical systems. The interaction between the message signals and the chaotic systems results in changes of different kinds of return maps. In this paper, we use return map based methods to unmask some chaotic secure communication systems; namely, chaotic shift keying (chaotic switching), chaotic parameter modulation and non-autonomous chaotic modulation. These methods are used without knowing the accurate knowledge of chaotic transmitters and without reconstructing the dynamics or identifying the parameters of chaotic transmitters. These methods also provide a criterion of deciding whether a chaotic secure communication scheme is secure or not. The effects of message signals on the changes of different return maps are studied. Fuzzy membership functions are used to characterize different kinds of changes of return maps. Fuzzy logic rules are used to extract message signals from the transmitted signal. The computer experimental results are provided. The results in this paper show that the security of chaotic secure communication not only depends on the complexity of the chaotic system but also depends on the way the message is scrambled. A more complex chaotic system is not necessary to provide a higher degree of security if the transmitted signal has simple and concentrated return maps. We also provide examples to show that a chaotic system with complicated return maps can achieve a higher degree of security to the attacks presented in this paper.

Synchronization of chaotic lasers by optical feedback for cryptographic applications

We propose a new scheme for synchronization of the optical chaos generated by a semiconductor laser subjected to external reflection. The scheme is based on optical feedback and will be analyzed from the viewpoint of static and dynamic properties and of robustness to external perturbations and noise. An application to cryptographic communications (chaotic shift keying) is finally proposed.

Synchronization of chaotic injected-laser systems and its application to optical cryptography

We demonstrate that two chaotic systems, each made by two coupled semiconductor lasers, can be synchronized using direct-optical feedback. The robustness of the proposed synchronization scheme against mismatch of source parameters and difference in starting conditions is tested by numerical simulations. Applications to secure data transmission are proposed, namely chaotic masking and chaotic shift keying (CSK).