Chaos has been one of the most effective cryptographic sources since it was first used in image-encryption algorithms. This paper closely examines the development process of chaos-based image-encryption algorithms from various angles, including symmetric and asymmetric algorithms, block ciphers and stream ciphers, and integration with other technologies. The unique attributes of chaos, such as sensitivity to initial conditions, topological transitivity, and pseudo-randomness, are conducive to cross-referencing with other disciplines and improving image-encryption methods. Additionally, this paper covers practical application scenarios and current challenges of chaotic image encryption, thereby encouraging researchers to continue developing and complementing existing situations, and may also serve as a basis of future development prospects for chaos-based image encryption.

Pseudorandom binary sequences play a significant role in many fields, such as error control coding, spread spectrum communications, and cryptography. In recent years, chaotic system is regarded as an important pseudorandom source in the design of pseudorandom bit generators (PRBGs). Among them, most are based on one or more fixed chaotic systems, and the generated binary sequences come to be stationary. However, these kinds of chaotic PRBGs can be attacked by reconstructing the phase space or using some statistical analysis methods. In this study, a scheme for chaotic PRBG based on non‐stationary logistic map is proposed. The authors design a dynamic algorithm to change the driven parameter sequence (not random) into a random‐like sequence. The variable parameters disrupt the phase space of the system, which can resist the phase space reconstruction attacks effectively. They prove that the non‐stationary logistic map is still chaotic under Wiggins’ chaos definition. The numerical analysis shows that the generated binary sequences have good cryptographic properties and can pass the well‐known statistical tests. The authors’ chaotic PRBG based on non‐stationary logistic map is a novel scheme in the design of PRBG, and is more secure than the PRBGs based on fixed chaotic systems.

One of the shortcomings of previous studies is that the encryption scheme proposed in them can only encrypt grayscale images at the pixel level. To address this limitation, the present study combines DNA computing with double-chaos systems and proposes an algorithm for color image encryption at the bit level. We use the improved double-chaos system composed of Lorenz chaotic mapping with variable parameters and fourth-order Rossler hyperchaotic mapping to generate three sets of chaotic sequences for the diffusion operation. The pseudo-randomness of the two types of chaotic mapping is compensated for. Then, we transform the chaotic component images and chaotic sequences into DNA sequences in accordance with eight DNA coding rules. We also perform addition, subtraction, and XOR operations on them. DNA computation can realize color image bit-level diffusion and reduce the computational cost. Simulation experiments are conducted with the proposed encryption scheme, and a detailed analysis is performed on histogram, key space, key sensitivity, correlation, information entropy, resistance to differential attacks, robustness, and algorithm complexity to prove the good performance of our image encryption algorithm. Results show that the proposed algorithm has good security performance and can effectively resist all types of attacks, indicating that the proposed algorithm is competitive.

The one‐dimensional (2D) chaotic encryption algorithm has good encryption performance. For its properties, such as the excellent complexity, pseudo‐randomness, and sensitivity to the initial value of the chaotic sequence. However, compared with other methods, its biggest drawback is that the key space is too small. To address these problems, in this study, the authors introduce an improved 2D logistic sine chaotic map (2D‐LSMM). A novel image encryption scheme based on dynamic DNA sequences encryption and improved 2D‐LSMM is presented. The logistic map is used to control the input of the sine map. And the encoding and operation rules of DNA sequences are determined by 2D‐LSMM chaotic sequences. By implementing dynamic DNA sequence encryption, the encryption process becomes more complicated and harder to be attacked. Simulation experimental results and security analysis show that the authors’ encryption scheme not only achieves proper encryption but can also resist different attacks.