Chaos-based image encryption

Abstract

Chaos-based encryption applications are at the forefront of engineering applications based on chaotic systems. When the studies in the literature are examined, it is seen that chaos-based image encryption applications are widely used. The randomness and unpredictable dynamic behavior of chaotic systems make chaos-based encryption applications very useful. For this reason, chaos-based image encryption is handled in a separate chapter here. In this chapter, first, continuous and discrete-time chaotic systems are mentioned and the chaos-based image encryption studies carried out in recent years are examined. The reason for this is to reflect the main effects of continuous-time or discrete-time systems on chaos-based image encryption. In addition, integer-order, fractional-order, and variable-order systems are also discussed and their use in image encryption applications is seen. Then, the methods used in encryption applications are introduced and the analysis methods used in chaos-based image encryption applications are explained. In the explanations about chaos-based image encryption applications, the commonly used steps for these applications are discussed. As these steps, numerical solutions of chaotic systems, random number generation operations, randomness tests, and encryption operations using the xor operation are explained. Security analysis, which is another process that needs to be performed regarding chaos-based image encryption, is also included in this chapter. In the literature, entropy, correlation, differential attack, histogram, keyspace analysis, which are the most widely used analysis methods for chaos-based image encryption, are explained. Although widely used in the literature, chaos-based encryption methods also have advantages and disadvantages. Therefore in this chapter, the security evaluation of chaos-based encryption algorithms is also presented. In particular, the convenience and effectiveness of these methods in practice are stated. On the other hand, the aspects that are not accepted according to the classical cryptology approach are also emphasized. Finally, a case study on medical images is handled with a chaos-based image encryption algorithm and the results of the case study are presented. In this application, numerical solutions and random numbers are obtained by using a classic 4D chaotic system. Then, the encryption process is carried out by xoring with the random numbers. The resulting encrypted image is analyzed and the results are presented.