Design and Practical Implementation of a Stream Cipher Algorithm Based on a Lorenz System

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Currently, the security of data has gained significant attention in modern life. Researchers have continued to address this issue. This work addresses image encryption in communication systems. It presents a proposed design and implementation of a cryptography system based on the Lorenz chaos oscillator. The paper methodology uses Xilinx System Generator (XSG) and Field Programmable Gate Array (FPGA) technologies to implement the chaotic system. To determine the approach that uses the least amount of FPGA resources while providing effective and efficient performance, the differential equations of the Lorenz chaotic system are solved via the forward-Euler and Runge–Kutta integration techniques. In the XSG environment, a secure communication system is constructed on the basis of the solution of the differential equations. After that, the planned communication system is implemented on the FPGA board and tested to encrypt images (coloured images). The histogram, entropy and other related security analysis factors are calculated and analysed to test the efficiency of the designed system. Six statistical methods were employed to provide a high level of image encryption in this work. Findings have shown that the proposed system generates (with stable, fast and robust performance) pseudorandom bits that can be successfully used to encrypt the data bits. The simulation and FPGA results are in good agreement; however, the security analysis factors prove that the system can be successfully adopted for image encryption purposes in real-time applications.