|Title of Invention||
A SYSTEM FOR PROVIDING SCRAMBLED CONTENT AND FOR DESCRAMBLING THE SCRAMBLED CONTENT
|Abstract||A system for providing scrambled content, comprising a control word generator, each control word including a control word identifier, a scrambler for providing a stream of scrambled data packets, and an encryption device for providing entitlement control messages (ECM's). One or more consecutive packets are scrambled using the same control word (CW). Each packet includes a control word identifier identifying the control word used. The ECM encryption device provides ECM’s including previous control word (CW<sub>p</sub>), a current control word (CW<sub>c</sub>) and a next control word (CW<sub>n</sub>). A system for descrambling scrambled content comprises a descrambler for descrambling the scrambled content and a decryption device for devrypting ECM’s to obtain control words to the descrambler and the descrambler descrambles the data packets of the scrambled content using a control word having a control word identifier corresponding with the control word identifier of the data packet to be descrambled.|
System for providing scrambled content, and system for descram-biing scrambled content
The invention relates to conditional access systems suitable for receiving apparatus provided with storage devices with large capacity. The invention specifically relates to a systerr. for providing scrarrbled content according to the pream¬ble of claim 1 and to a system for descrambling scrambled con¬tent according to the preamble of claim 3.
identifier identifying the control word used, and an encryption device for providing entitlement control messages (ECM's), each ECM including at least a next control word (CWH) , characterized
in that the ECM encryption device provides ECM's including a previous control word (CWp) , a current control word (CWc) and a next control word (CWs) .
invention is shown.
Fig. lA and IB show simplified diagrams of erri^odiments of the systems for providing scrambled content, and descram-bling scrambled content according to the invention.
Fig. 2A and 2B shown diagrams to explain the operation of the svstems of the invention.
Fig. 1 shows a system 1 for providing scrambled con¬tent comprising a control word generator 2 and a scrambler 3. The scrambler 3 receives clear content and delivers content scrambled using the control words provided by the control word
The descrambling system 5 comprises a descrambler 6 for descrambling the scrambled content and a decryption device 7 for decry-pting ECM's to obtain the control v;ords CW. This de¬vice 7 can be made as a smart card. Further, the system 5 com.-prises a processing unit 8 controlling the operation of the system and having a schematically indicated control means 9 al¬lowing control of the system by the user. The scrambled content is received by the processing unit 8 and can be stored on a storage device 10, for example a hard disc with large capacity.
According to Che invention, this problem of locating an ECM in the data stream is avoided by including in the ECM' s three keys, i.e. the previous control word CWp, the current control word CWc and the next control word CWn. In this manner each ECM extracted from the stream by the processing unit 3 at play back of the content stored on the disc 10 contains three control words, including the control v/ord required for descram-bling the previous data packet. In this manner a rewind func¬tion is supported in an easy manner so that the user can scroll back through the content retrieved from the storage device 10 using the control m;eans 9. Of course, such control m^eans may include a remote control device.
An illustration of the operation of the systems of the invention is schematically shown in fig. 2. A content stream with data packets A, 3, C and D is shown, wherein it is assumed that data packet A has the control word identifier G, the data
backwards, i.e. a VCR-like rewind function, the processing unit 3 instructs the decryption device 7 to provide the current con¬trol word CWAO and previous control word CWpi. In this manner the descrambler 6 can descramble the previous data packet.
In the above example it is indicated that the ECM's are stored as part of the content. It is also possible to store the ECM's separately with timing information. In this case tim¬ing information in the content stream is used by the processing unit 8 to extract or retrieve the correct ECM's from the stor¬age device 10.
From the above it will be understood that the inven¬tion provides systems, wherein going backwards through the stored video content is allowed without any significant in¬crease in the load en the processing unit in processing ECM's and synchronizing control words. It will be clear that the in¬vention can be used with any type of video or audio content.
The invention is not restricted to the above described embodiments which can be varied in a number of ways within the scope of the attached claims.
1. System fcr providing scrambled content:, comprising a concrol word generator, each control word including a control word identifier, a scrambler for providing a stream of scram¬bled data packets, wherein one or more consecutive packets are scrambled using the same control word (CW) and wherein each packet includes a control word identifier identifying the con¬trol word used, and an encrv-ption device for providing entitle¬ment control messages ECM's), each ECM including at least a next control word (CWn) , characterized in that the ECM encryp¬tion device provides ECM's including a previous control word (CWp) , a current control word (CW,-) and a next control word (CWJ:) .
unit is programmed to request the ECM decryption device to pro¬vide the current control word (CWc) together with a next con¬trol word (CWN) at playback or going fast forward and to pro¬vide the current control word (CWc) together with a previous control word (CW2) at going backwards.
5. System according to claim 3 or 4, wherein the SCM decryption device is accommodated in a smart card.
6. System for providing scrambled content substantially as herein
described with reference to the accompanying drawings.
7. System for descrambling scrambled content substantially as
herein described with reference to the accompanying drawings.
|Indian Patent Application Number||IN/PCT/2002/1810/CHE|
|PG Journal Number||50/2007|
|Date of Filing||05-Nov-2002|
|Name of Patentee||M/S. IRDETO ACCESS B.V|
|Applicant Address||Jupiterstraat 42, NL-2132 HD Hoofddorp,|
|PCT International Classification Number||H04N 5/76|
|PCT International Application Number||PCT/EP2001/003186|
|PCT International Filing date||2001-03-21|