Ciphertext-policy attribute-based delay encryption

Timed-release CP-ABE can provide fine-grained and timed-release access control while ensuring data confidentiality. Existing schemes usually rely on a trusted third-party called time server. This paper proposes a novel timed-release CP-ABE scheme named ciphertext-policy attribute-based delay encryption (CP-ABDE), which does not require a time server. Specifically, we formalise the notion of CP-ABDE and its system model and security model. Furthermore, we provide a formal construction that is secure under the decisional bilinear Diffie-Hellman assumption and repeated squaring assumption. Finally, performance analysis shows that the scheme performs well while achieving timed-release access control.