Copy count for DTCP with an abbreviation hash used for check in copy
A Digital Rights Management (DRM) system is provided that reduces time for a move transaction using DTCP-IP when a copy is moved back or checked back in to an originating Personal Video Recorder (PVR). During a DTCP MOVE transaction, instead of transferring the full asset in a check back in operation to the PVR, a unique and abbreviated representation of the original copy of the asset would be made for the transfer. This abbreviated representation takes the form of a hash constructed from a hashing function which uses characteristics of the asset as inputs. This hash will have to be a unique and near guaranteed indicator of the original content, to a high probability, so that the copy control system could live up to the spirit of the DTCP spec and the DLNA interoperability guidelines.
1. A method for controlling copy count using a Digital Transmission Content Protection (DTCP) standard, the method comprising:
maintaining an original master copy of a first video content in a personal video recorder (PVR);
maintaining a copy count number;
copying the original master copy as a copy asset and transferring the copy asset from the PVR to a second video device on request for check out by the second video device and marking the transferred copy asset as Copy No More (CNM), and decrementing the copy count, and further creating and storing an abbreviated representation of the copy asset in the PVR and the second video device;
receiving the copy asset checked back in to the PVR from the second video device in response to a MOVE command, the received copy asset being the abbreviated representation of the checked-out copy from the second video device; and
comparing the checked in copy asset with the abbreviated representation stored in the PVR to determine if the checked in copy asset is from the identical first video content, and if so incrementing the copy count,
wherein the abbreviated representation takes the form of a hash constructed from a hashing function, and
wherein the abbreviated representation can be regenerated with the copy asset alone as an input to the hashing function.
2. The method of claim 1 ,
wherein a transfer from the PVR occurs under a Sync n' Go command and the transferred copy is bound with the original copy so that the copy count is decremented when either the copy asset or the original master copy are transferred.
3. The method of claim 1 ,
wherein the copy asset checked into the PVR occurs under a Sync n' Go command, and
wherein both the original copy and the copy asset are maintained in storage in the PVR.
4. The method of claim 1 , wherein the abbreviated representation comprises at least one of (a) a CRC based hash function; (b) a cryptographic hash; and (c) an additive arithmetic hash operation.
5. The method of claim 1 , wherein the copy asset is a transcoded version of the original master copy.
6. The method of claim 1 , wherein the hash function is created using an algorithm provided from or identified by the PVR to the second video device.