Device and procedures for key renewal in a hierarchical tree key structure

摘要

An information recording/reproducing device for executing a key distribution by a KRB distribution involving a tree-structure key distribution configuration. The device transmits, by using a key-structure key distribution configuration, a key such as a master key, a media key or a content key along with a key update block (KRB). The recording/reproducing device, after calculating and acquiring the key of a certain recording medium based on a reception KRB, encrypts the acquired key using an encryption key specific to the device, for example, a leaf key, and stores it in a recording medium or memory of the device. Therefore, the recording/reproducing device can calculate a key by merely decoding the encrypting key one time when next using the recording medium or contents, and can reduce computational complexity such as KRB decoding required when the device accesses a recording medium or uses contents, thereby making efficient processing on the KRB receiving side.