US Patent 8738536 Licensing content for use on portable device

A computing device has encrypted content and a corresponding license having a decryption key for decrypting the content. The license allows the computing device to render the content thereon. The computing device may issue a sub-license based on the license to a portable device. The sub-license allows the portable device to render the content thereon and has the decryption key. The portable device has a digital device certificate including information thereon. The computing device receives from the portable device the device certificate thereof, and determines based on rules in the license and the information on the portable device in the device certificate whether the computing device can issue the sub-license to the portable device. If so, the computing device constructs such sub-license to include the decryption key (KD) and transmits the constructed sub-license to the portable device.