Chaos has unpredictability and initial condition sensitivity, which known as a best candidate for cryptography application. However, there are many defects for the existing chaotic cryptography systems due to the use of chaotic maps that without complexity dynamic properties. To overcome these weaknesses, this work designed a 2D-SCMCI hyperchaotic map based on Cascade Modulation Couple (CMC) and two 1D-chaotic map. The dynamic characteristics of the 2D-SCMCI hyperchaotic map are analyzed through attractor trajectory, 0-1 test, bifurcation diagram, Lyapunov exponents and spectrum entropy (SE) complexity. The results of analysis indicate that 2D-SCMCI hyperchaotic map has rich dynamic performance and randomness, which illustrates that it is more suitable for image encryption algorithm. Therefore, an image encryption algorithm is proposed by 2D-SCMCI hyperchaotic map. In encryption algorithm, the image is scrambled by row and column, forward and backward diffusion are used to diffuse image pixel values. The security performances analysis results indicate that the introduced algorithm has better security characteristics.

In this paper, an associated color chaotic image encryption algorithm is proposed according to a twodimensional chaotic system and random XOR diffusion. Firstly, the initial value of the 2D-Logistic-Sine-Coupling map (2D-LSCM) is generated by the SHA-256 and the key stream is generated by the 2D-LSCM. The three channels (red, green, blue) of the color image are processed into a matrix. The key stream is used in the color image scrambling phase according to the cyclic shift. Third, do random XOR diffusion according to the mathematical expression of the 2D-LSCM. In this step, nonlinear diffusion is used, and the scrambling is included in the diffusion. Each pixel value of the ciphertext is XORed by three values, which are the key stream, a pixel value of the scrambled image and the position of the pixel value is different from the position of the ciphertext pixel value, and a non-adjacent ciphertext pixel value. Finally, the statistical analysis is used to test the algorithm. Experimental results show that the algorithm not only reduces the correlation between adjacent pixels, but also reduces the correlation between the three channels of a ciphertext. Compared with some classic algorithm, the algorithm proposed in this paper is more secure.

3D image is a kind of image closer to life, and 3D image has a stronger visual impact. In the past, researchers mostly protected flat images, but ignored the protection of 3D images. This paper combines the 2D chaotic system and uses random cross diffusion to propose a new encryption algorithm for 3D images which are STL format. Different from the traditional scrambling and diffusion operations, this paper uses only one iterative operation to achieve the effects of scrambling and diffusion, making the algorithm more secure. In the encryption algorithm, each value of the ciphertext is XORed with the value of the plaintext on the same coordinate axis and different from the coordinate where the ciphertext is located, the chaotic sequence, the ciphertext of different coordinate axes significantly reduces the correlation between the adjacent coordinate values. In addition, the proposed 3D image encryption algorithm is tested by statistical analysis. The experimental results show that this 3D image encryption algorithm has high security.