Transformation between Attribute-Based Encryption and Key-Aggregate Cryptosystem

Generic construction of cryptographic primitives is a way to connect two research areas. The problems in one area may be solved in the other area if such connections are built. In this manuscript, two generic constructions of attribute-based primitives are proposed. First, we give a bi-directional conversion between a key-aggregate cryptosystem and a key-policy attribute-based encryption with OR-gate-only access structures. Second, we give a generic construction of a ciphertext-policy attribute-based key encapsulation mechanism (CP-ABKEM) from a key-aggregate key encapsulation mechanism. Moreover, the proposed CP-ABKEM supports expressive access structures. Based on our conversion, we can construct the first ciphertext-policy attribute based key encapsulation mechanism with constant-size private keys.