FACOR is a new solution that enables flexible access control on outsourced data in mobile clouds using attribute-based encryption. It allows mobile users to outsource expensive encryption and decryption computations to proxies while only requiring full trust of attribute authorizations. FACOR also provides an outsourceable revocation process for mobile users to reduce the complexity of attribute-based revocations. The scheme achieves data security against collusion attacks and unauthorized access from revoked users.