Abstract
In this paper, the parameter-switching technique was applied to control chaos in the Chen oscillator and as a decryption mechanism in a secure transmission system, to transmit RGB and grayscale images. In the past few decades, considerable efforts have been put into the study of the stabilization of chaotic dynamical systems. Most of the well-known chaos control methods, such as Ott, Grebogi, and Yorke (OGY), Pyragas, and open-loop methods, force an unstable periodic orbit into a stable one while distorting the original attractor. On the other hand, the parameter-switching technique is an elegant method that can synthesize an already-existing stable orbit, thereby preserving the underlying attractor. Consequently, the main contributions of this work were the FPGA realizations of the parameter-switching method and a secure image transmission system using a synchronized master and slave topology. The results of the parameter-switching technique and synchronization were verified using phase plots and time series. The chaos-encrypted image from the image transmission system, verified using correlation, showed no relativity with the original image, while the recovery of the decrypted image has no loss of quality. The encryption and decryption system was symmetric, whereby the key was private. In this work, co-simulations were performed in Active-HDL with MATLAB/Simulink, while the target FPGA board was the Xilinx’s Artix-7 AC701.
Highlights
The digital implementation of the parameter-switching scheme as the chaos control mechanism was highlighted in this paper
Parameter switching can function as the chaos anti-control mechanism, whereby two or more underlying stable attractors are combined to synthesize a chaotic attractor
The second major contribution was the field-programmable gate array (FPGA) realization of a secure communication system whereby the parameter-switching scheme was applied as a decryption mechanism to recover chaos-encrypted RGB and grayscale images
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In the past few years, considerable efforts, both theoretical and experimental, have been devoted to how to stabilize chaotic dynamical systems, whereby the orbits change a little under small perturbations of a parameter The authors investigated the application of the parameter-switching technique in approximating the stable dynamics of the Chen oscillator and its usefulness in a chaos-based image transmission system, with a view of a digital implementation on an FPGA device. FPGA realization of the parameter-switching scheme to approximate the stable cycles of the Chen oscillator, using VHDL as the implementation language with a word length of 24 bits, on the Xilinx’s Artix-7 AC701 board. The VHDL implementation on the FPGA board agreed completely with the numerical simulations done in MATLAB; FPGA realization of a secure chaos-based image transmission system on the Xilinx’s.
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