Medical Data Security in Blockchain: A Telemedicine Data Sharing Scheme Based on Custom OPE and 4D-YG Hyperchaotic

Aiming at the problems of sensitive data leakage and unauthorised direct access faced during the storage and transmission of shared medical data, this paper proposes a new medical data security sharing scheme based on blockchain. Firstly, to ensure the security and randomness of the keys in the scheme, a new 4D-YG hyperchaotic key generator is designed. Secondly, self-expanding fractal Sierpinski triangle permutating operation is performed on medical images to achieve image decentring effect. Utilize a custom Order-Preserving Encryption (OPE) algorithm to diffuse it, ensuring consistency in pixel order before and after encryption. Subsequently, mix-bit triple normalized diffusion is performed on the images that have completed preliminary diffusion to enhance the resistance of privacy data within the image to attacks. Finally, the decryption permission for encrypted shared medical data is restricted through smart contracts in the blockchain. While achieving secure transmission of medical data, it enables hospitals to perform medical image segmentation and organ recognition diagnostics on shared data in an encrypted state, which is more in line with practical needs. According to performance test data, the proposed encryption algorithm can effectively resist differential attacks and frequency attacks, and the Number of Pixels Change Rate (NPCR) test results can reach the ideal value of 99.6094%.