1. A method comprising: maintaining, by a trusted gateway device logically interposed between an enterprise network and a plurality of third-party cloud storage services, a file storage policy for each user of a plurality of users of the enterprise network, wherein the plurality of file storage policies define access rights, storage diversity requirements and types of encryption to be applied to files stored to the plurality of third-party cloud storage services on behalf of respective users of the plurality of users; and responsive to receiving, by the trusted gateway device, a request to store a local file from a user of the plurality of users: creating, by the trusted gateway device, searchable encrypted data corresponding to one or more of (i) content of the local file and (ii) metadata associated with the local file, wherein the searchable encrypted data is based on a type of encryption defined by a file storage policy of the plurality of file storage policies assigned to the user; and distributing, by the trusted gateway device, the searchable encrypted data among the plurality of third-party cloud storage services based on a storage diversity requirement defined by the file storage policy by uploading a subset of the searchable encrypted data to each of the plurality of third-party cloud storage services.