Functional Encryption for Bounded Collusions, Revisited.

We provide a new construction of functional encryption (FE) for circuits in the bounded collusion model. In this model, security of the scheme is guaranteed as long as the number of colluding adversaries can be a-priori bounded by some polynomial Q. Our construction supports arithmetic circuits in contrast to all prior work which support Boolean circuits. The ciphertext of our scheme is sublinear in the circuit size for the circuit class (mathsf{NC}_1); this implies the first construction of arithmetic reusable garbled circuits for (mathsf{NC}_1).