Smart Contracts - Cloud Storage-Assisted Medical Image Encryption and Sharing Solution

Abstract

To address the security risks in sharing medical imaging data and the challenges of insufficient data interoperability between heterogeneous systems, and to achieve secure sharing of medical information across institutions, this paper proposes a secure encryption scheme based on the characteristics of medical images, and uses cloud storage and smart contracts to build a secure framework for cross-institutional information sharing. First, in response to the regional characteristics and uneven information distribution of medical images, an innovative two-stage encryption scheme of “partitioning, diffusion, and coupled scrambling” is proposed. The first stage applies information entropy equalisation processing to non-ROI regions, enhancing their information effectiveness and generating dynamic parameters. The second stage utilises the cross-region coupling dynamic parameters generated in the first stage to optimise the encryption results within ROI regions. Finally, a key driven scrambling factor is employed to complete the global pixel position reconstruction, achieving high-security encryption. Each medical institution encrypts medical images and uploads them to unified cloud storage, along with binary thumbnails generated from the corresponding plaintext images. Simultaneously, essential metadata—including image hash values, ownership details, and access permission policies—is stored on the blockchain. After an authorized user selects the desired data by browsing cloud thumbnails, a smart contract automatically executes the transaction, completing on-chain permission verification, data traceability, and access authentication, thereby coordinating the user's secure access to the corresponding encrypted image data off-chain. Eight experiments have demonstrated the security of the encryption scheme and the proposed sharing framework.