Fully secure key-policy attribute-based encryption with constant-size ciphertexts and fast decryption

Attribute-based encryption (ABE), introduced by Sahai and Waters, is a promising cryptographic primitive, which has been widely applied to implement fine-grained access control system for encrypted data. In its key-policy flavor, attribute sets are used to annotate ciphertexts and secret keys are associated with access structures that specify which ciphertexts a user is entitled to decrypt. In most existing key-policy attribute-based encryption (KP-ABE) constructions, the size of the ciphertext is proportional to the number of attributes associated with it and the decryption cost is proportional to the number of attributes used during decryption. In this paper, we present a new construction of KP-ABE. Our proposed construction is the first KP-ABE scheme, which has the following features simultaneously: expressive (i.e., supporting arbitrary monotonic access structures); fully secure in the standard model; constant-size ciphertexts and fast decryption. The downside of our construction is that secret keys have quadratic size in the number of attributes