US Patent 7743261 Unauthorized contents detection system

An executing device conducts playback of contents. The executing device is equipped with a highly efficient processor and reduces the processing load involved in verification by using, for the verification, only a predetermined number of encrypted units selected randomly from multiple encrypted units constituting encrypted contents recorded on a DVD. In addition, the executing device is capable of improving the accuracy of detecting unauthorized contents by randomly selecting a predetermined number of encrypted units every time the verification is performed.