Optimizing Attribute-Based Encryption for Circuits Using Compartmented Access Structurese

Attribute-based encryption (ABE) is an asymmetric encryption method that allows expressive access granting mechanisms, with high applicability in modern IT infrastructure, such as Cloud or IoT systems. (Ezhilarasi et al., 2021; Touati and Challal, 2016) One open problem regarding ABE is using Boolean circuits as access structures. While Boolean Formulae were supported since the first ABE scheme proposed, there is still no efficient construction that supports Boolean circuits. We propose a new ABE scheme for a new access structure type, situated between Boolean formulae and Boolean circuits in terms of expressiveness. This key point in our construction is the usage of CAS-nodes, a structure modeling compartmented groups access structures. We also show that our CAS-nodes can be used to improve the efficiency of existing ABE schemes for Boolean circuits. Our construction is secure in the Selective Set Model under the bilinear Decisional Diffie-Hellman Assumption.