Patent ID: 7792292
Filing Date: 2010-09-07
Classification: G06F,H04N

Abstract:
1. An electronic device comprising: a storage unit storing right information for managing whether or not a content can be played back, the right information being stored in a state protected from unauthorized accesses; a receiving unit operable to receive a plurality of frames that constitute the content in an encrypted state, each frame of the plurality of frames being received one by one; a right judging unit operable to perform a judgment of whether or not the content is permitted to be played back, the judgment being performed in accordance with the right information; and a control unit operable to (a) control the right judging unit to perform the judgment for every Nth received frame of the plurality of frames when a value of N satisfies a predetermined judgment condition, wherein the value of N is a natural number of 2 or more and indicates a position of a frame of the plurality of frames in an order of playback of the plurality of frames constituting the content, (b) decrypt the Nth received frame when the right judging unit judges that the content is permitted to be played back, and (c) restrict the playback of frames located after the Nth received frame of the plurality of frames when the right judging unit judges that the content is not permitted to be played back, wherein the right information includes playback total time information and playback right time information, the playback total time information indicating a playback total time that is a total time of the playback of the content having been performed, the playback right time information indicating a playback right time, the playback right time being a time period for which the content is permitted to be played back, wherein the right judging unit performs the judgment by comparing the playback right time with a sum of the playback total time and an elapsed time, the elapsed time being a time that has elapsed while the content has been played back, wherein the control unit includes a right updating sub-unit operable to update the playback total time information stored in the storage unit according to the elapsed time, the playback total time information being updated in a process of decrypting the Nth received frame when the value of N satisfies a predetermined update condition, wherein the electronic device further comprises a right temporary storage unit having a storage area that is accessible at a higher speed than the storage unit, wherein the control unit stores, in the right temporary storage unit, the right information stored in the storage unit, wherein the right judging unit performs the judgment in accordance with the right information stored in the right temporary storage unit, wherein the right updating sub-unit performs a first process to update the playback total time information stored in the right temporary storage unit according to the elapsed time, and performs a second process to store, in the storage unit, the updated right information stored in the right temporary storage unit, wherein the control unit, in the process of decrypting the Nth received frame, controls the right updating sub-unit to perform either the first process or the second process, or both the first process and the second process, depending on the value of N, wherein the control unit performs a third process to cause the right judging unit to perform the judgment, prohibiting the right updating sub-unit from performing any of the first process and the second process, and performs a fourth process to (i) prohibit any of the third process, the first process by the right updating sub-unit, and the second process by the right updating sub-unit, and (ii) decrypt the Nth received frame, and wherein the control unit performs, in each process of decrypting a frame of the plurality of frames, one of the third process, the fourth process, the first process by the right updating sub-unit, the second process by the right updating sub-unit, and both the first process and the second process by the right updating sub-unit.