Search

In this paper identical and generalized synchronization and the complex dynamics of hyperchaotic circuits are exploited for designing reliable cryptosystems. Since chaotic additive masking, chaotic switching and chaotic parameter modulation methods can have a low degree of security, an attempt to overcome this drawback is made by utilizing hyperchaotic circuits which make available several chaotic signals. Some of these signals are used to properly synchronize the encrypter and the decrypter in an identical and generalized way. Other chaotic signals are considered for encrypting and decrypting the information messages by means of a multishift cipher scheme. The approach is applied to a communication system constituted by an encrypter and a decrypter each consisting of two coupled Chua's circuits, unidirectionally coupled with two coupled Chua's oscillators. Simulation results are reported to show the performance of the suggested cryptosystem.

In this paper an approach to achieve a complete practical synchronization of hyperchaotic circuits with parameter mismatch via an impulsive scalar signal is presented. The chosen scalar signal is constituted by a sequence of samples of selected state variables alternatively transmitted for identical time frames. The approach is effectively applied to hyperchaotic circuits with parameter mismatch constituted by two bidirectionally coupled Chua's oscillators.

In this paper a DTCNN-based vision system for pattern recognition in an artificial vision architecture is illustrated. The bipolar images, segmented in a preprocessing stage, constitute the input to a cellular associative memory in the recognizing stage of the vision system. The performance of DTCNNs designed as associative memories is confirmed by means of examples of detection and recognition of tools handled by a robot in an assembly line.

In this paper a synthesis technique for the synchronization of hyperchaotic circuits with application to secure communications is developed. It is well known that information-bearing signals can be considered as causes of perturbations, when a secure communication system based on a masking technique is implemented. Starting from this consideration, in this paper a feedback control scheme is developed to guarantee synchronization between transmitter and receiver. The control scheme involves as many state variables in the feedback as the number of information signals to be transmitted. After deriving the nonlinear dynamics of the synchronization error system, the feedback matrix is determined by finding a suitable Lyapunov function and by imposing the conditions which assure the global asymptotic stability of the origin of the error system. The method is illustrated by considering hyperchaotic circuits constituted by coupled Chua's oscillators, for which analytic expressions of the feedback gains are derived.

In this paper an efficient method is illustrated to obtain a secure communication system by means of the synchronization of hyperchaotic circuits. The approach consists in driving the receiver with a proper number of transmitted signals, each of them constituted by a chaotic masking waveform added to an information-bearing signal, and by keeping the transmitting system equivalent to the receiving one by means of a feedback technique. The suggested method assures a recovery of the information signals without degradation, and enhances the security of the communication scheme, since the utilization of several driving signals makes more difficult for an undesirable listener to synchronize with the transmitter. Simulation results are reported to confirm the capability of the proposed approach.