Patent ID: 8335315
Filing Date: 2012-12-18
Classification: H04L

Abstract:
1. A decryption method comprising: requesting, by a device that corresponds to a predetermined node among a plurality of nodes in a node tree and has at least one key allocated to the predetermined node, an external device other than the device to perform a part of a decryption process of decrypting encrypted contents, the part of the decryption process comprising examining whether only the at least one key allocated to the predetermined node has been revoked; and performing, by the device, a remaining part of the decryption process, that is not performed by the external device, of decrypting the encrypted contents based on a response to the request received directly from the external device, wherein the device retains a part of information required to perform the part of the decryption process, the external device retains a remaining part of the information required to perform the part of the decryption process, and the requesting the external device to perform the part of the decryption process comprises transmitting a request message containing the part of the information to the external device, and wherein the part of the decryption process further comprises decrypting an encrypted content key that encrypts the contents, and the performing the remaining part of the decryption process of decrypting of the encrypted contents comprises receiving the response to the request including the decrypted content key and decrypting the encrypted contents using the decrypted content key.