US Patent 8184811 Mobile telephony content protection

In a digital content management system, a mobile device determines whether it is authorized to use digital content by sending, to a service provider, a hash value that has been pre-stored in the mobile device and that is associated with the digital content. The hash value is generated by combining a user identifier, among other data, into a combined hash. The other data included in the combined hash may be, for example, a service provider key unknown to the user, and a hash of the protected content. A telecommunications service provider, such as a service provider of a CDMA wireless network, determines whether the hash value is valid and, accordingly, whether the mobile device is authorized to use the digital content.