Verifiable and Accountable Multi-Authority CP-ABE with Consent Binding and Revocation for Cloud EHR

In regulated cross-institution electronic health record (EHR) sharing, access control may need to respect patient consent while also providing issuance accountability and revocation correctness. Existing multi-authority ciphertext-policy attribute-based encryption (MA-CP-ABE) schemes provide decentralized attribute management but generally do not bind key issuance and ciphertext use to explicit patient-authorized sharing episodes, nor do they provide proactive verification that accepted key packages are consistent with authenticated user requests and the current revocation state. In this paper, we propose a verifiable, consent-bound MA-CP-ABE scheme for cloud-assisted EHR sharing. The scheme binds ciphertexts and attribute key packages issued to a patient-signed consent identifier, supports request-consistent and verifiable key issuance, integrates revocation freshness and stale-key detection, and provides a two-layer accountability framework consisting of proactive issuance verification together with reactive tracing and audit. In addition, each issued package is bound to the enrolled user public key and to a user-originated commitment, supporting restricted designated-user delivery. Theoretical and experimental evaluations indicate that, under the stated trust and non-collusion assumptions, the proposed design strengthens consent-scoped access control and accountability while maintaining competitive computational efficiency for cloud-based EHR systems.