Abstract:
A method for securing a content is disclosed. The method generally includes the steps of (A) generating a media key by decrypting a media key block based on a device key unique to a particular player of a plurality of players, (B) modifying the media key by decryption based on a class key such that the media key is unique for each of a plurality of subscriber classes, (C) writing an encrypted title key in a media by encrypting a title key based on both the media key after modification and a media identification value unique to the media and (D) writing an encrypted content in the media by encrypting the content based on the title key.

Description:
[0001]     This application claims the benefit of U.S. Provisional Application No. 60/579,131, filed Jun. 10, 2004, which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to controlled access systems generally and, more particularly, to a content security system for screening applications.  
       BACKGROUND OF THE INVENTION  
       [0003]     Limited distributions of new movies, recently filmed scenes and various programs for award ceremony voting use extraordinary security measures to ensure that the contents are only seen by authorized viewers and to keep the contents from being bootlegged. Recordable DVD-video disks are a popular method for limited distribution since the people receiving the disks is known. Distributions range from entire movies to specific scenes filmed a few hours earlier. The recent scenes are commonly referred to as “digital dailies”. Internet distribution is also utilized where digital dailies are transmitted from remote filming locations back to studios for executive review. Unfortunately, control of the DVD disks and Internet transmissions can be compromised resulting in unauthorized copies becoming available to the public.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention concerns a method for securing a content. The method generally comprises the steps of (A) generating a media key by decrypting a media key block based on a device key unique to a particular player of a plurality of players, (B) modifying the media key by decryption based on a class key such that the media key is unique for each of a plurality of subscriber classes, (C) writing an encrypted title key in a media by encrypting a title key based on both the media key after modification and a media identification value unique to the media and (D) writing an encrypted content in the media by encrypting the content based on the title key.  
         [0005]     The objects, features and advantages of the present invention include providing a content security method and system for screening applications that may (i) provide a high degree of control over content screening, (ii) frustrate unauthorized digital copying, (iii) corrupt unauthorized analog copying, (iv) provide forensic evidence in unauthorized copies, (v) provide revokable authorization and/or (vi) provide a hierarchical class structure of permissions. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     These and other objects, features and advantages of the present invention will be apparent from the following detailed description and the appended claims and drawings in which:  
         [0007]      FIG. 1  is a block diagram of a system in accordance with a preferred embodiment of the present invention;  
         [0008]      FIG. 2  is a flow diagram of an example implementation of an authoring process for a secure content;  
         [0009]      FIG. 3  is a block diagram of an example implementation of a video player; and  
         [0010]      FIG. 4  is a block diagram of an example implementation of a player. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0011]     Referring to  FIG. 1 , a block diagram of a system  100  is shown in accordance with a preferred embodiment of the present invention. The system  100  generally comprises a recorder  102 , one or more players  104   a - 104   n , a disk media  106 , a card media  108 , an optional server  110  and an optional network  112 . The network  112  may connect the recorder  102  to the server  110 . The network  112  may also connect the server  110  to the players  104   a - 104   n  (generically referred to as the players  104 ). The disk media  106  may be physically transferred from the recorder  102  to a particular one of the players  104  (e.g., a player  104   a ). The card media  108  may be transferred along with the disk media  106  to the particular player  104   a . The recorder  102  may receive a signal (e.g., IN) containing a content to be authored, distributed and controlled. The content may include video streams, audio streams and/or related data. Each player  104  authorized to play the content may generate a signal (e.g., OUT) carrying the content. The recorder  102  may be operational to generate a secured content from the received content. The secured content may be transferred to the players  104  via the disk media  106  and/or the server  110  over the network  112 . Additional security information may be transferred to the players  104  via the card media  108  and/or the server  110  over the network  112 .  
         [0012]     The disk media  106  may be implemented as an optical disk media. In one embodiment, the disk media  106  may be a DVD-video (DVD-V) disk, a DVD-Rewritable (DVD-RW) disk, a DVD-ROM disk, a DVD-Video Recording (DVD-VR) disk, and Enhanced Versatile Disk (EVD) or the like. The disk media  106  may be designed to be physically incompatible with conventional DVD readers, such as in personal computers and home entertainment systems. Other forms of media, such as tape and cassettes, may be implemented to meet the criteria of a particular application.  
         [0013]     The card media  108  may be implemented as a smart card. In one embodiment, the smart card  108  may be compliant with an International Organization for Standardization (ISO) standard 7816. In another embodiment, the smart card may be implemented as a Universal Serial Bus (USB) plug-in module. The plug-in module implementation may include an optional USB modem for Internet-based authentication and may carry new firmware to distribute security upgrades to the players  104 . Other designs of the card media  108  may be implemented to meet the criteria of a particular application. The smart card  108  generally allows for limited and total renewability, including recovery from a system-wide hack, by exchanging the smart cards  108 . The smart card  108  may provide a mechanism for a user entered password to enable decryption. As such, an unauthrorized user in possession of an authorized player  104  may be prevented from viewing the protected content. Authentication of the password may be based on information stored in (i) the disk media  106 , (ii) the player  104  or (iii) the server  110 .  
         [0014]     The server  110  may be referred to as a license server. The license server  110  may be operational to authenticate the players  104  and provide keys to the authenticated players  104 . The license server  110  may also be operational to store the secured content and associated information is if stored on the disk media  106 . In one embodiment, transportation of the secured content may thus be performed over the network  112  instead of physical movement of the disk media  106 .  
         [0015]     For network-based operations, a disk media  106  may be inserted into a player  104 , an optional password entered, and a “play” function started. A modem in the player  104  may contact the license server  110  and perform mutual authentication. The player  104  may transmit a player identification value, a media identification (ID) value stored in the disk media  106 , a Control Access System (CAS) identification (ID) value stored in the smart card  108  and the password to the license server  110 . The license server  110  may verify a playback permission, calculate a transaction ID value (e.g., 40-bit value) and send both the transaction ID value and a class key (e.g., back to the player  104 .) A log in the license server  110  may record the transaction along with the associated player ID value, media ID value, date, time and CAS ID value. Transmission of the class key may be protected by an Authenticated Key Exchange (AKE)-over-IP process. The playback authorization may persist for a few hours and then self-terminate. The transaction ID value may be used in a video watermark payload present in virtually all frames and on all outputs of the player  104 .  
         [0016]     The system  100  generally provides studio-controlled creation and distribution of the secured content. The secured content may be generated using a studio-proprietary encryption implemented in the recorder  102 . The studio-proprietary encryption may restrict copying of the secured contents from the disk media  106  for transmissions on the network  112 . Publicly-vetted cipher and key management schemes may be utilized in the system  100 .  
         [0017]     Playback of the secured content may be limited by studio-controlled distribution of the players  104 , disk media  106  and the smart cards  108 . The players  104  may implement a studio-proprietary decryption. In general, the players  104  may be distributed to award voters, studio production people and other people intended to view some or all of the secured content. Each of the players  104  may be associated with an individual user, by name, for (i) traceability to a source of unauthorized copies and (ii) revoking conditional access when appropriate. Session-based forensically-traceable watermarks may be provided on all outputs at the player  104  using a frequency-domain technology developed by MediaSec (Providence, R.I.) and VeriMatrix (San Diego, Calif.). Other watermarks, such as pixel domain watermearking, may be implemented to meet the criteria of a particular application. Playback may be restricted to classes of subscribers established by authentication.  
         [0018]     Distribution of the players  104 , disk media  106  and the smart cards  108  may be kept relatively small in volume. The smart card  108  may be used to authenticate playback of the secured content stored in the disk media  106  for one or more players  104 . The smart card  108  may allow the studio to renew conditional access and/or revoke access to the content. Information transported by the disk media  106  and in the smart card  108  may permit playback in one or more authenticated classes of subscribers.  
         [0019]     Referring to  FIG. 2 , a flow diagram of an example implementation of an authoring process  120  for a secure content is shown. The authoring process (or method)  120  generally comprises a step (or block)  122 , a step (or block)  124 , a step (or block)  126 , a step (or block)  128 , a step (or block)  130 , a step (or block)  132 , a step (or block)  134 , a step (or block)  136 , a step (or block)  138 , a step (or block)  140 , a step (or block)  142 , a step (or block)  144 , a step (or block)  146 , a step (or block)  148 , a step (or block)  150  and a step (or block)  152 . The authoring process  120  may be implemented in the recorder  102 .  
         [0020]     A description of the authoring process  120  may start with reading (e.g., step  122 ) a Media Key Block (MKB) file and the media ID value from the disk media  106 . Both the MKB file and the media ID value may be prerecorded on the disk media  106 . A particular device key may be determined (e.g., step  124 ) from a set of device keys defined by the MKB file. The particular device key may uniquely identify a target player  104  being authorized to view the secured contents. The set of device keys generally identifies all potential players  104  that may be authorized.  
         [0021]     The particular device key may be used to determine a media key by decrypting the MKB file (e.g., step  126 ). The media key may be modified (e.g., step  128 ) using a class key. The class key may be written (e.g., step  130 ) in the smart card  108  and/or transferred (e.g., step  132 ) to the server  110 .  
         [0022]     A secret title key may be encrypted (e.g., step  134 ) based on both the modified media key and the media ID value to provide an encrypted title key. The encrypted title key may be written (e.g., step  136 ) in the disk media  106  and/or transferred to the server  110  (e.g., step  138 ).  
         [0023]     One or more control bits (or a control value) may be added (e.g., step  140 ) to the content. The control value may establish one or more permissions for the players  104 . The permissions may include, but are not limited to, a view and listen-only permission, a view-only permission, a listen-only permission, a copy permission, password protection permission and the like.  
         [0024]     One or more protection bits (or a protection value) may be added (e.g., step  142 ) to the content. The protection value may enable/disable an analog protection mechanism in the players  104  designed to frustrate copying of an analog signal representation of the content. In one embodiment an Analogue Protection System (APS), developed by Macrovision Corporation (Santa Clara, Calif.), may be implemented to add information to an analog output of the players  104  that confuses automatic gain control and/or synchronization circuitry in video cassette recorders.  
         [0025]     The title key may be used to encrypt (e.g., step  144 ) the content, with the embedded control value and protection value, to generate the secured content. The secured content may also be referred to as an encrypted content. The encrypted content may be written (e.g., step  146 ) in the disk media  106  and/or transferred (e.g., step  148 ) to the server  110 .  
         [0026]     An enable value may be written (e.g., step  150 ) in the smart card  108  and/or transmitted (e.g., step  152 ) to the server  108  in an enabled state (e.g., a predetermined value or a presence in the media). The enabled state generally instructs the players  104  that a media key should be decrypted before being used to decrypt the encrypted title key. The enable value in a disabled state (e.g., a predetermined value or an absence from the media) generally instructs the players  104  not to modify the media key.  
         [0027]     Where the secured content is written on the disk media  106 , the media ID value used to encrypt the title key may bind the secured content to the disk media  106 . The device key used to decrypt the media key from the MKB file generally binds the secured content to the particular player  104 . The class key in the smart card  108  generally enables decryption of the secured content on the players  104  and authenticates a class of subscriber to view the playback of the decrypted content.  
         [0028]     Where the secured content is stored in the server  110 , the media ID, MKB file, encrypted title key and the encrypted content, with the embedded control value and the protection value, may be treated as if stored on the disk media  106 . For example, the media ID, MKB file, encrypted title key and the encrypted content may be transmitted to the players  104  in the same sequence as would be read from the disk media  106 .  
         [0029]     In one embodiment, the recorder  102  may implement a modified Content Protection for Removable Media (CPRM) encryption process. The modified CPRM may securely bind the content to a particular disc media  106 . The binding generally frustrates disc-to-disc copying, bit-for-bit copying and peer-to-peer file sharing. Other encryption techniques may be implemented to meet the criteria of a particular application.  
         [0030]     Referring to  FIG. 3 , a block diagram of an example implementation of a first player  104   s  is shown. The payer  104   s  may be any of the players  104   a - 104   n  and may be implemented as a video player. The player  104   s  generally comprises a loader (or drive)  160 , a circuit (or module)  162   a  and an optional circuit (or module)  164 . An interface  166  of the player  104   s  may be configured to connect with the smart card  108 . An output  167  of the player  104   s  may provide one or more audio signals (e.g., AUDIO). An output  168  of the player  104   s  may provide the video signal OUT. An interface  169  of the player  104   s  may be configured to connect with the network  112 .  
         [0031]     The loader  160  may be operational to read the disk media  106 . The loader  160  may be an optical disk drive, magnetic drive, or other mass storage device. The circuit  162   a  may be referred to as a codec circuit. The codec circuit  162   a  may be implemented as a single system-on-chip die to frustrate hacking attempts. The circuit  164  may be referred to as a network interface circuit. The network interface circuit  164  may be operational to communicate on the network  112 . The codec circuit  162   a  may receive data from the loader  160  read from the disk media  106  and/or data from the network interface circuit  164  received across the network  112 . The network circuit  164  may also present a transaction ID value (e.g., TRANSID) to the codec circuit  162   a.    
         [0032]     The codec circuit  162   a  generally comprises a circuit (or module)  170 , a circuit (or module)  172 , a circuit (or module)  174 , a circuit (or module)  176   a , a circuit (or module)  178   a , a circuit (or module)  180   a , a circuit (or module)  182   a  and a circuit (or module)  184 . The circuit  170  may be referred to as a cipher circuit. The cipher circuit  170  may be operational to decrypt the encrypted content (e.g., ECNT), present the content (e.g., CNT) to the circuits  176   a  and  182   a , present the media key (e.g., MKEY 1 ) to the circuit  172 , receive a modified media key (e.g., MKEY 2 ) from the circuit  172  and receive an alternate title key (e.g., TK 2 ) from the circuit  174 . In one embodiment, the cipher circuit  170  may be operational to implement a modified CPRM decryption process.  
         [0033]     The circuit  172  may be referred to as a modification circuit. The modification circuit  172  may be operational to generate the modified media key MKEY 2  based on the media key received from the cipher circuit  170  and a class key (e.g., AESKEY) received from the circuit  174 . The modified media key MKEY 2  may be returned to the cipher circuit  170 . In one embodiment, the modification circuit  172  may implement an Advanced Encryption Standard (AES) decryption.  
         [0034]     AES-encryption of the media key MKEY 1  before encrypting the title key (e.g., TK 1 ) may make the modified media key MKEY 2  unique for each class of screener subscriber. The modified media key MKEY 2  may have a different value in each of the players  104   s . Only authorized players  104   s  may recalculate the proper media key MKEY 2  for decrypting the secret title key TK 1  stored on the disc media  106 .  
         [0035]     The circuit  174  may be referred to as a smart card interface circuit. The smart card interface circuit  174  may be operational to read the class key AESKEY, the enable value (e.g., ENABLE) and a conditional access system (CAS) identification (ID) value (e.g., CASID) unique to the smart card  108 . The class key AESKEY may be presented to the modification circuit  172 . The value ENABLE may be presented to the cipher circuit  170 . The CAS ID value may be presented to the circuit  178   a.    
         [0036]     The circuit  176   a  may be referred to as a video decoding circuit. The video decoding circuit  176   a  may be operational to perform video decoding of the content received from the cipher circuit  170  to generate an intermediate video signal (e.g., S 1 ). The video decoding circuit  176   a  may also perform subpicture decoding. In one embodiment, the video decoding circuit  176   a  may implement an MPEG-2 compliant decoding. In another embodiment, the video decoding circuit  176   a  may implement an H.264/AVC-10 compliant decoding. Other coding standards may be implemented to meet the criteria of a particular application. The video signal S 1  may be presented to the circuit  178   a.    
         [0037]     The circuit  178   a  may be referred to as a watermark circuit. The watermark circuit  178   a  may be operational to watermark select frames of the video signal S 1  received from the video decoding circuit  178   a . The watermarking may embed one or more of a date (e.g., Julian date), a player identification value (e.g., PID) unique to each of the players  104 , the CAS ID value and/or a transaction ID value (e.g., TRANSID) into the frames. A watermarked video signal (e.g., S 2 ) may be presented to the circuit  180   a . Additional details regarding watermarking may be found in copending U.S. patent application Ser. No. 10/______ (Attorney Docket no. 1497.000397), filed Dec. 20, 2004 and hereby incorporated by reference in its entirety.  
         [0038]     The circuit  180   a  may be referred to as a video digital to analog converter (DAC) circuit. The video DAC circuit  180   a  may be operational to convert the watermarked video signal S 2  into an analog signal (e.g., the video signal OUT) at the output  168 . The video DAC circuit  180   a  may implement the APS system by Macrovision when enabled through the protection value. The APS system anti-taping capability should be enabled when operating on content authored by the recorder  102 . The player  104   s  may respond to the APS bits even for discs not protected by a Content Scrambling System (CSS) process.  
         [0039]     The circuit  182   a  may be referred to as an audio decoder circuit. The audio decoder circuit  182   a  may be operational to decode audio and other information from the reconstructed content receive from the cipher circuit  170 . The signal AUDIO may be presented at the output  167 .  
         [0040]     The circuit  184  may be referred to as a control circuit. The control circuit  184  may be operational to control the video decoding circuit  176   a  and the audio decoding circuit  182   a  based on the control value received from the cipher circuit  170 . Control over the video and audio decoding may be used to implement related permissions, such as video-only and audio-only permissions.  
         [0041]     The cipher circuit  170  generally comprises a circuit (or module)  190 , a circuit (or module)  192 , a circuit (or module)  194  and a circuit (or module)  196 . The circuit  190  may be referred to as a first decryption circuit. The first decryption circuit  190  may be operational to decrypt the MKB file based on a device key unique to the player  104   s  to generate the media key.  
         [0042]     The circuit  192  may be referred to as a gate circuit. The gate circuit  192  may be operational to pass/block the media key MKEY 1  to the circuit  194  in response to the value ENABLE. When the enable value is asserted in the enabled state, the gate circuit  194  may block a path for the media key MKEY 1  between the first decryption circuit  190  and the circuit  194 . When the enable value is deasserted in a disabled state, the gate circuit  194  may pass the media key MKEY 1  directly from the first decryption circuit  190  to the circuit  194 . Bypassing the modification circuit  172  generally allows a player  104  to decrypt content protected by the conventional CSS technique.  
         [0043]     The circuit  194  may be referred to as a second decryption circuit. The second decryption circuit  194  may be operational to decrypt an encrypted title key (e.g., ETK) based on the media key (modified or not) and the media ID value to reconstruct the title key TK 1 . The title key TK 1  may be presented to the circuit  196 .  
         [0044]     The circuit  196  may be referred to as a third decryption circuit. The third decryption circuit  196  may be operational to perform a conventional class C 2  decryption (provided by the U.S. National Computer Security Center, Ft. Meade, Md.) on the encrypted content ECNT based on the title key TK 1  received from the second decryption circuit or the alternate title key TK 2  received from the smart card interface circuit  174 . C 2  encryption (recorder  102 ) and decryption (players  104 ) generally binds the content to the players  104 . The C 2  cipher may associate the content with a particular player  104  such that the secured content may not play back on any other player  104 .  
         [0045]     When the gate circuit  192  is passing the media key MKEY 1  unaltered, a combination of the first decryption circuit  190 , the second decryption circuit  194  and the third decryption circuit  196  may implement the CPRM decryption to accommodate conventional CPRM protected recordings satisfying a 4C license. The CPRM decryption may also accommodate conventional CSS-protected DVD-Video titles. The modified CPRM process may be transparent to a subscriber viewing the content. For example, trick features such as fast forward and pause may all work as normally.  
         [0046]     The permission value may provide hierarchically classified tiered permissions to separate screener classes by studio, by project, or similar classifications. For example, classes may include, but are not limited to, Digital Dailies, Award voters, post-production departments and project producers. Classes may also allow studio executives to view any project from their own company. The permission value may also establish permission for playback-only or record in secure format. Corresponding classes may be established for other industries, such as the television industry.  
         [0047]     Referring to  FIG. 4 , a block diagram of an example implementation of a second player  104   t  is shown. The player  104   t  may be similar to the player  104   s  but configured to operate on non-video type data. The non-video type data may include, but is not limited to, viewable data, non-viewable data and audio data. The player  104   t  may be any of the players  104   a - 104   n.    
         [0048]     The player  104   t  generally comprises the loader (or drive)  160 , a circuit (or module)  162   b  and the optional circuit (or module)  164 . The interface  166  of the player  104   t  may be configured to connect with the smart card  108 . The output  167  of the player  104   t  may provide one or more audio signals (e.g., AUDIO). The output  168  of the player  104   t  may provide a signal (e.g., OUT 2 ). The interface  169  of the player  104   t  may be configured to connect with the network  112 .  
         [0049]     The circuit  162   b  generally comprises the cipher circuit  170 , the modification circuit  172 , the smart card interface circuit  174 , a circuit  176   b , an optional circuit  178   b , a circuit  180   b , a circuit  182   b  and the control circuit  184 . The interface  166  of the player  104   t  may be configured to connect with the smart card  108 .  
         [0050]     The circuit  176   b  may be referred to as a rendering circuit. The rendering circuit  176   b  may be operational to perform a rendering of the content received from the cipher circuit  170  to generate the intermediate signal (e.g., S 1 ). In one embodiment, the rendering circuit  176   b  may be operational to render non-video content such as, but not limited to, subscription research reports, scripts, blueprints, still photos, schematic drawings, equity analysis reports, pre-release books, data files, audio streams and the like. For example, the rendering circuit  176   b  may convert the content into a conventional PDF, JPG or TIFF format. In another embodiment, the rendering circuit  176   b  may include a decoding capability. The intermediate signal S 1  may be presented to the circuit  178   b.    
         [0051]     The circuit  178   b  may be referred to as a watermark circuit. The watermark circuit  178   b  may be operational to watermark the content of the intermediate signal S 1  received from the rendering circuit  176   a , where appropriate. The watermarking may embed one or more of a date (e.g., Julian date), a player identification value (e.g., PID) unique to each of the players  104   t , the CAS ID value and/or a transaction ID value (e.g., TRANSID) and an indication of confidentiality. The watermarking may be visible, subtle or non-visible depending on the application and/or the keys, class, subclass or a network enable command. A watermarked intermediate signal (e.g., S 2 ) may be presented to the circuit  180   b . The watermark circuit  178   b  may be eliminated (e.g., signal S 2 =signal S 1 ) in applications having content not suitable for watermarking.  
         [0052]     The circuit  180   b  may be referred to as an output driver circuit. The output driver circuit  180   b  may be operational to convert the watermarked intermediate signal S 2  into a signal (e.g., the signal OUT 2 ) suitable for transmission, reproduction and/or storage. For example, the output driver circuit  180   b  may be a printer driver, a television monitor driver (e.g., a component output driver for a high-definition television), a network driver, a storage device driver or similar driver suitable to generate the signal OUT 2  for a particular application.  
         [0053]     The circuit  182   b  may be referred to as an audio decoder circuit. The audio decoder circuit  182   b  may be operational to decode audio information from the reconstructed content receive from the cipher circuit  170 . The signal AUDIO may be presented at the output  167 .  
         [0054]     The players  104  may provide a forensically-traceable, session-based watermarks or real-time traceable watermarks. The watermarking generally associates the content with an originating player  104 , a date, and a particular smart card module  108 . Every playback frame of video may be watermarked (e.g., 100,000 to 200,000 frames per film). The redundancy in watermarks generally increases a degree of certainty at a detection phase. Discrete Cosine Transform (DCT) coefficient pairs may be manipulated to implement the watermarks, provided the change is not too visible. Embedded signal strength may also be adjusted in accordance with local image activity to avoid visibility.  
         [0055]     The watermarking may embed one or more bits in select 8×8 transfer blocks. The watermark circuit  178   a  generally watermarks approximately 30 to 40 blocks per frame in real time during playback, depending on computational complexity of a perceptual model and the embedding may be performed entirely on-chip (e.g., no external path to hack or bypass). Fractional bits per block may also be used in comparing coefficients across different macroblocks or pictures. An example watermark payload may include: 
        Player-unique ID 17 bits=131,000 players     Julian date 12 bits=11 years     CAS ID 18 bits=262,000 modules 
 
 An approximately 29-bit to 47-bit total watermark payload may be generated to help identify the player  104  involved in unauthorized copying. 
       
 
         [0059]     Forensic detection and tracking software may be executed on a workstation to examine a suspected illegal copy. Records of embedding procedures may be maintained to aid in the watermark detection. For example, records may be kept to identify where the watermark signal was embedded and locations of coefficient manipulations may be known in advance for each title.  
         [0060]     In cases where high volume distribution is involved (e.g., distribution to Award Screeners), DVD-ROM disks may be utilized with the media ID value being unique per master disk (e.g., unique per stamping run). In one embodiment, a Burst Cutting Area (BCA) in the disk media  106  may be written to store a unique media ID value for each disk.  
         [0061]     Conventional DVD-Video authoring may be used to take advantage of available encoding and authoring tools. The modified CPRM encryption may be performed by the recorder  102  after the authoring.  
         [0062]     The function performed by the flow diagram of  FIG. 2  and the block diagrams of  FIGS. 3 and 4  may be implemented using a conventional general purpose digital computer programmed according to the teachings of the present specification, as will be apparent to those skilled in the relevant art(s). Appropriate software coding can readily be prepared by skilled programmers based on the teachings of the present disclosure, as will also be apparent to those skilled in the relevant art(s).  
         [0063]     The present invention may also be implemented by the preparation of ASICs, FPGAs, or by interconnecting an appropriate network of conventional component circuits, as is described herein, modifications of which will be readily apparent to those skilled in the art(s).  
         [0064]     The present invention thus may also include a computer product which may be a storage medium including instructions which can be used to program a computer to perform a process in accordance with the present invention. The storage medium can include, but is not limited to, any type of disk including floppy disk, optical disk, CD-ROM, magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, Flash memory, magnetic or optical cards, or any type of media suitable for storing electronic instructions.  
         [0065]     While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention.