Relying on Trust to Balance Protection and Performance in Cryptographic Access Control

Cryptographic Access Control (CAC) allows organizations to control cloud-hosted data sharing among users while preventing external attackers, malicious insiders, and honest-but-curious cloud providers from accessing the data. However, CAC entails an overhead often impractical for real-world scenarios due to the many cryptographic computations involved. Hence, we put forth a hybrid Access Control (AC) scheme --- combining CAC and (traditional) centralized AC --- that considers trust assumptions (e.g., on users) and data protection requirements of the underlying scenario on a case-by-case basis to reduce the number of cryptographic computations to execute in CAC. Besides, we design a consistency check to ensure the correctness and safety properties of the enforcement of the hybrid AC scheme, provide a proof-of-concept implementation in Prolog, and conduct a preliminary experimental evaluation.