Current image encryption methods have many shortcomings for the medical image encryption with high resolution, strong correlation and large storage space, and it is difficult to obtain reliable clinically applicable medical images. Therefore, this paper proposes a medical image encryption algorithm based on a new five-dimensional three-leaf chaotic system and genetic operation. And the dynamic analysis of the phase diagram and bifurcation diagram of the five-dimensional three-leaf chaotic system selected in this paper is carried out, and NIST is used to test the randomness of its chaotic sequence. This algorithm follows the diffusion-scrambling framework, especially using the principle of DNA recombination combined with the five-dimensional three-leaf chaotic system to generate a chaotic matrix that participates in the operation. The bit-level DNA mutation operation is introduced in the diffusion, and the scrambling and diffusion effects have been further improved. Algorithm security and randomness have been enhanced. This paper evaluates the efficiency of this algorithm for medical image encryption in terms of security analysis and time performance. Security analysis is carried out from key space, information entropy, histogram, similarity between decrypted image and original image, PSNR, correlation, sensitivity, noise attack, cropping attack and so on. Perform time efficiency analysis from the perspective of time performance. The comparison between this algorithm and the experimental results obtained by some of the latest medical image encryption algorithms shows that this algorithm is superior to the existing medical image encryption algorithms to a certain extent in terms of security and time efficiency.

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In order to improve the security of image transmission, this paper proposes a self-adaptive image encryption scheme based on chaos and gravitation model. The proposed scheme consists of three stages: key generation stage, double scrambling stage, and double diffusion stage. In the key generation stage, the plaintext-associated key generation mechanism (BPPAKG) based on the bit plane is used to obtain the key associated with the plaintext. Since the key ultimately depends on the plaintext image itself, this scheme has self-adaptability. The first stage of scrambling uses mixed chaotic transform and shift row transform to disturb pixel position, then changes the pixel value of the image based on the concept of gravitation to achieve the first stage of diffusion. To enhance the security performance of the scheme, the traditional encryption structure is extended, and the second stage of scrambling and diffusion is quickly realized by using diagonal scanning transform and XOR operation. Simulation and experimental results show that the scheme has good encryption and decryption performance and strong resistance to attack. In addition, compared with some latest proposed algorithms, it has better security.