<p>With the continuous advancement of digital healthcare, the application of Internet of Things and cloud storage technologies has enabled the sharing of personal health data, thereby simplifying patient care and improving operational efficiency. However, sharing medical data through cloud storage still faces several challenges, including key management issues, performance bottlenecks caused by a single centralized authorization authority, and the lack of mechanisms for tracing and revoking malicious users. These issues may lead to data breaches. This paper proposes a revocable blockchain-based multi-authority access control scheme that combines Multi-Authority Attribute-Based Encryption with blockchain technology to address these challenges. The proposed scheme eliminates the key management problem through a keyless management mechanism, ensuring that no single authority fully controls the encryption keys. The security analysis and simulation results indicate that the proposed scheme outperforms other comparative schemes, proving it to be a feasible solution.</p>