Attribute-Hiding Predicate Encryption in Bilinear Groups, Revisited

We present new techniques for achieving strong attribute-hiding in prime-order bilinear groups under the standard k-Linear assumption. Our main result is a “partially hiding” predicate encryption scheme for functions that compute an arithmetic branching program on public attributes, followed by an inner product predicate on private attributes. This constitutes the first “best of both worlds” result in bilinear groups that simultaneously generalizes existing attribute-based encryption schemes and inner product predicate encryption. Our scheme achieves a variant of simulation-based security in the semi-adaptive setting. Along the way, we introduce a conceptually simpler and more modular approach towards achieving the strong attribute-hiding guarantee.