Improved AB‐CPREs with Revocability and HRA Security under LWE
Yang Wang, Mingqiang Wang · IET Information Security · 2024
Attribute‐based conditional proxy re‐encryption protocols (AB‐CPREs) enable a delegator to delegate his decryption rights via different policies and grant the data owner greater flexibility in allocating their encrypted private data stored in the cloud. However, existing lattice‐based AB‐CPREs suffer from some drawbacks such as large parameters and weak passive securities. To the best of our knowledge, the first quantum‐safe key‐policy AB‐CPREs with polynomially bounded parameters (for certain NC 0 circuits/policies) that is selective attribute secure against honest re‐encryption attacks (HRA) is presented. The security of our proposed AB‐CPREs is based on standard LWE assumptions. We further introduce the directly revocable AB‐CPREs, a primitive that enables a delegator to authorize and revoke his delegation of decryption rights dynamically and offers more flexible access control on externally stored encrypted data. Definition and security model of single‐hop directly revocable AB‐CPREs are given, and the first detailed construction of single‐hop directly revocable AB‐CPREs based on standard LWE assumptions is also proposed.