Securing E-health Data using Ciphertext-Policy Attribute-Based Encryption with Dynamic User Revocation

E-health systems hold a massive amount of medical data that is stored and shared across healthcare service providers to deliver health facilities. However, security and privacy worries increase when sharing this data over distributed settings. As a result, Cryptography techniques have been considered to secure e-health data from unauthorized access. The Ciphertext Policy Attribute-Based Encryption (CP-ABE) is commonly utilized in such a setting, which provides role-based and fine-grained access control over encrypted data. The CP-ABE suffers from the problem of user revocation where the entire policy must be changed even when only one user is revoked or removed from the policy. In this paper, we proposed a CP-ABE based access control model to support user revocation efficiently. Specifically, the proposed model associates a unique identifier to each user. This identifier is added to the policy attributes and removed dynamically when the user is added/revoked. A tree structure (PolicyPathTree) is designed specifically for our model. It can facilitate fast access to policy's attributes during the verification process; The model is analyzed using Information Theory Tools. Results show that our model outperforms other notable work in terms of computational overheads.,