Patent Publication Number: US-6912513-B1

Title: Copy-protecting management using a user scrambling key

Description:
BACKGROUND 
   1. Field of the Invention 
   The present invention is related to copy protection. In particular, the present invention is related to copy protection using scrambling keys. 
   2. Description of Related Art 
   Copy protection management provides mechanisms to prevent unauthorized copying of clear content. In a typical scenario, a content provider supplies a content to a user via a medium. The medium may be a communication medium such as air, a communication network, or a hardware device, e.g. DVD disk, embodying the content. The content is scrambled by the content provider in a certain way. The scrambled content is then delivered the user&#39;s reader or viewing device. The user&#39;s reader or viewing device unscrambles the scrambled digital content and provides the content in the clear for viewing reading, or listening. The clear digital content would typically have copy protection applied to it such as Digital Transmission Copy Protection (DTCP) or watermarking. The copy protection, for example, could limit copying of the clear content to “Copy Never” or “Copy Once”. 
   Conditional access (CA) devices are those user&#39;s viewing, reading, or listening devices that provide conditional access to the content. Entitlement management messages (EMM) typically use unique keys or signatures to deliver privileges (e.g., rights, keys) to a particular CA device. Typically, in broadcast systems, a group entitlement right of group key would be delivered to the CA device. Typically the group are users or customers who share a particular set of entitlements, e.g. HBO or Disney. 
   Current copy protection schemes allow the copying of CA scrambled content as “Copy Free”. Yet the CA unscrambled content may or may not be copiable based on the Copy Protection status of the content. A content provider may choose to mark certain types of CA unscrambled content as “Copy Never” where there can never be copying of the CA unscrambled content. In such an approach, the content stored and kept in CA scrambled format. There are a number of problems with such a copy protection approach. 
   First, if the content is locally scrambled with a unique CA key or unique access right in a particular CA device, then it is difficult to play back the content in another CA device located elsewhere. As an example, in a home environment, if a set-top box has a unique CA key or access right to de-scramble the content delivered by a cable service provider, then only that particular set-top box can provide access to the content. Other set-top boxes located elsewhere (e.g., other rooms, or in the car, or portable devices like a Walkman) cannot access the content. 
   Second, if the CA device with a unique CA key or unique access right fails to work for any reason, then the content stored with, or received by, that device may not be retrievable. A user&#39;s entire archive of movies, music, and other content stored with that unique CA key or unique access right of a particular CA device nay be lost. These and other problems create inconveniences and frustrations for the user, and may also limit the services provided by the content provider. 
   Therefore, there is a need for a more flexible for handling copy protected content to accommodate multiple access devices. 
   SUMMARY 
   The present invention is a method and apparatus for providing copy protection for a content. A descrambler descrambles the content delivered by a content provider using a local key. A key generator is coupled to the descrambler to generate the local key from a programmable user key according to an authorization code provided by the content provider. 
   In one embodiment, each user is assigned a user key which may be programmed into various devices owned by that user. The user key is used to descramble locally stored content. Scrambled content may be copied since only the devices owned by the user, containing the user key, can unscramble the content. The content may be delivered to the user or household scrambled under the user key. Alternatively, the content may also be delivered under a group entitlement or broadcast key, however when stored locally, the content is reprocessed with the user key. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will become apparent from the following detailed description of the present invention in which: 
       FIG. 1  is a diagram illustrating a system in which one embodiment of the invention can be practiced. 
       FIG. 2  is a diagram illustrating a digital receiver according to one embodiment of the invention. 
       FIG. 3  is a diagram illustrating a control processor unit according to one embodiment of the invention. 
       FIG. 4  is a diagram illustrating a conditional access unit according to one embodiment of the invention. 
       FIG. 5  is a flowchart illustrating a process for copy protection for a master CA device according to one embodiment of the invention. 
       FIG. 6  is a flowchart illustrating a process for copy protection for a second CA device according to one embodiment of the invention. 
   

   DESCRIPTION 
   The present invention is a method and apparatus to provide copy protection for a content. The content is provided by a content provider. A descrambler descrambles the scrambled content using a local key. In one embodiment, each user is assigned a user key which may be programmed into various devices owned by that user. The user key is used to descramble locally stored content. Scrambled content may be copied since only the devices owned by the user, containing the user key, can unscramble the content. The content may be delivered to the user or household scrambled under the user key. Alternatively, the content may also be delivered under a group entitlement or broadcast key, however when stored locally, the content is reprocessed with the user key. 
   A key generator is coupled to the descrambler to generate the local key from a user key according to an authorization code provided by the content provider. In one embodiment of the invention, a communication interface provides the authorization code to the key generator via a communication channel. The technique allows a user to use his or her user key to access a scrambled content with authorized conditional access (CA) devices. 
   In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known architectures, steps, and techniques have not been shown where unnecessary for an understanding of the present invention. For example, specific details are not provided as to whether the method is implemented in a station as a software routine, hardware circuit, firmware, or a combination thereof. 
   Embodiments of the invention may be represented as a software product having program code segments to perform the necessary tasks corresponding to the elements of the present invention. The program or code segments can be stored in a processor readable medium or transmitted by a computer data signal embodied in a carrier wave, or a signal modulated by a carrier, over a transmission medium. The processor or machine readable medium may include any medium that can store or transfer information. Examples of the processor readable medium include an electronic circuit, a semiconductor memory device, a ROM, a flash memory, an erasable ROM (EROM), a floppy diskette, a compact disk CD-ROM, an optical disk, a hard disk, a fiber optic medium, a radio frequency (RF) link, etc. The processor or machine readable medium may contain various sets of instructions, code sequences, configuration information, or other data. Those of ordinary skill in the art will appreciate that other instructions and operations necessary to implement the described invention may also be stored on the machine-readable medium. The computer data signal may include any signal that can propagate over a transmission medium such as electronic network channels, optical fibers, air, electromagnetic, RF links, etc. The code segments may be downloaded via computer networks such as the Internet, Intranet, etc. 
     FIG. 1  is a diagram illustrating a system  100  in which one embodiment of the invention can be practiced. 
   The system  100  includes a program data receiver  110 , a transmission medium  120 , an audio system  130 , a digital video recorder or player  140 , a disk recording unit  150 , a display  160 , a control unit  170 , and a network CA unit  180 . 
   The program data receiver  110  includes a digital receiver  112  and a decoder  114 . The digital receiver  112  receives digital bitstream or data including program data from one or more service providers. Such service or content providers may include terrestrial broadcasters, cable operators, direct broadcast satellite (DBS) companies, companies providing content for download via the Internet, book publisher, software companies distributing software products, or any similar content and/or service provider. The program data may include system information, entitlement control messages, entitlement management messages, content, and other data. System information may include information on program names, time of broadcast, source, method of retrieving and decoding, copy management commands that provide digital receivers and other devices that control how, when, and what program data may be replayed, retransmitted, copied, and/or recorded. These copy management commands may also be transmitted along with entitlement control messages (ECM), which are generally used by the conditional access unit to regulate access to a particular channel or service. Entitlement management messages (EMM) may be used to deliver privileges to the digital receiver  112  such as rights and de-scrambling keys. As known, a decryption or de-scrambling key is generally a code that is required to restore the scrambled data, and may be a function of the rights granted. Finally, content in the program data may include audio and video data, which may be in s scrambled or encrypted or clear format. The decoder  114  receives the extracted program data from the digital receiver  112 . The decoder  114  separates the system information from the content, decodes or decompresses the content to its original form. In one embodiment, the program data receiver  110  is a television set where the digital receiver  112  is a set-top box integrated therein, and the decoder  114  is a Motion Picture Experts Group (MPEG) decoder. 
   The transmission medium  120  operates to transmit control information and data including program data between the program data receiver  110  and other components in the system  100 . The transmission medium  120  may include air, fiber optics, electronic and magnetic media, computer network connection, telephone connection, and any other communication media. 
   The audio system  130  is coupled to the transmission medium  130  to provide audio services. The audio system  130  may include speakers, an audio player/recorder such as a compact disk player, or other magneto-optical disc that may be used to play and/or record audio data. The digital video recorder/player  140  is coupled to the transmission medium  120  to provide video services. The digital video recorder/player  140  may be used to record analog or digital video, audio, and other data transmissions. In one embodiment, the digital video recorder/player  140  may be used to replay or record the program data received by the program data receiver  110  and transmitted over the transmission medium  120 . 
   The disk recording unit  150  may also be coupled to the program data receiver  110  and other components via the transmission medium  120 . The disk recording unit  150  may be a personal computer system, a stand-alone hard disk recording unit, or other disk recording device capable of recording analog or digital audio, video and data transmissions, including the program data received and transmitted by the program data receiver  110 . 
   The display  160  may include a television display, a monitor display or other devices capable of processing and displaying video signals. In one embodiment, the display  160  is a digital television set. The control unit  170  may also be coupled to the transmission medium  120  to coordinate and control the operation of some or each of the components on the system  100 , as well as other devices remotely coupled thereto. 
   The network conditional access (CA) unit  180  may also be coupled to the transmission medium  120 . The network CA unit  180  operates to re-scramble program data with content in clear format such that the system  100  supports the simultaneous transmission of program data in clear and scrambled format. The network CA unit  180  may be a CA device that operates as a second CA device in a system embodiment where the program data receiver  110  operates as a master CA device. 
     FIG. 2  is a diagram illustrating a digital receiver  112  according to one embodiment of the invention. The digital receiver  112  includes a control processing unit  210 , a tuner  220 , a demodulator  230 , a conditional access (CA) unit  240 , and a demultiplexer  250 . 
   The control processing unit  210  performs control functions for the tuner  220 , the CA unit  240  and the demultiplexer  250 . The control processing unit  210  may determine the frequency in which a channel is broadcast or otherwise transmitted. The control processing unit  210  may support a graphical user interface (GUI), such as electronic programming guide (EPG) to allow a user to navigate through various channels and program options to select a desired channel or program for viewing, listening, recording and the like. The control processing unit  210  may contain a copy protection manager that provides copy protection for multiple CA devices according to one embodiment of the present invention. 
   The tuner  220  selects a frequency of the signal received by the program data receiver  110  (in  FIG. 1 ) under the control of the control processing unit  210 . The tuner  220  processes, amplifies, digitizes, and generates a bitstream to the demodulator  230 . 
   The demodulator  230  demodulates the bitstream received from the tuner  220  to provide the program data as originally transmitted. The type of demodulation performed by the demodulator  230  depends on the type of transmission as well as the modulation process used in the transmission process. Examples of the demodulation includes quadrature amplitude modulation (QAM) demodulation, quadrature phase shift key (QPSK) demodulation, and vestigial side band (VSB) demodulation. In addition, the demodulator  230  may perform error correction on the received bitstream. 
   The conditional access unit  240  may be integral or external to the digital receiver  112 . The CA unit  240  provides conditional access to the program data as provided by the demodulator  230 . The program data is typically scrambled using an access key. The CA unit  240  may be used in an external or split mode. In the external mode, the CA unit  240  de-scrambles the program data content and decrypts the keys externally; e.g., as is the case with the National Renewable Security System (NRSS) conditional access modules. In a split conditional access unit, the program data content is de-scrambled within the digital receiver  112 , while the key decryption is done externally, e.g., via a smart card. 
   The demultiplexer  250  receives the de-scrambled or unscrambled content from the CA unit  240 . The demultiplexer  250  separates the system information from the content in the program data, and according to one embodiment, parses the program data for packet identifiers that are associated with the system information, audio information, and video information, and then transmits the system information to the control processing unit  210  and the audio and video information to the decoder  114  (in FIG.  1 ). 
     FIG. 3  is a diagram illustrating a control processor unit  210  according to one embodiment of the invention. The control processor unit  210  includes a processor  305 , a host bus  310 , a host bridge chipset  320 , a system memory  330 , a peripheral bus  340 , a mass storage device  350 , and K peripheral devices  360   1  to  360   K . Although the control processor unit  210  is shown external to the conditional access unit  240  (in FIG.  2 ), it can be implemented as part of the CA unit  240 . 
   The processor  305  represents a central processing unit of any type of architecture, such as complex instruction set computers (CISC), reduced instruction set computers (RISC), very long instruction word (VLIW), explicitly parallel instruction set computing (EPIC), or hybrid architecture. The invention could be implemented in a multi-processor or single processor computer system. 
   The host bridge chipset  320  includes a number of interface circuits to allow the host processor  305  access to the system memory  330  and the peripheral bus  340 . The host bridge chipset  320  may include a memory controller and an I/O controller. The memory controller provides an interface to the system memory  330 . The I/O controller provides control of I/O functions. 
   The system memory  330  represents one or more mechanisms for storing information. For example, the system memory  330  may include non-volatile or volatile memories. Examples of these memories include flash memory, read only memory (ROM), or random access memory (RAM). The system memory  330  contains a copy protection manager  332 , a program  334  and a data  336 . Of course, the system memory  330  preferably contains additional software (not shown), which is not necessary to understanding the invention. 
   The peripheral bus  340  provides bus interface to the mass storage device  350  and peripheral devices  360   1  to  360   K . In one embodiment, the peripheral bus  160  is the peripheral component interconnect (PCI) bus. 
   The mass storage device  350  include CD ROM, floppy diskettes, and hard drives. The mass storage device  350  stores non-volatile information such as programs or data. The mass storage device  350  provides a mechanism to read machine or processor readable media, including a computer program product comprising a computer usable medium having computer program code embodied therein to provide copy protection management. The peripheral devices  360   l  to  360   K  include other peripheral devices or controllers such as network interface device, printer controller, keyboard, mouse, tablet digitizer, etc. 
     FIG. 4  is a diagram illustrating a conditional access unit  240  according to one embodiment of the invention. The CA unit  240  includes a de-scrambler  410 , a key generator  420 , and a communication interface  430 . 
   The de-scrambler  410  receives the scrambled content, such as the bitstream provided by the demodulator  230  shown in  FIG. 2 , and de-scrambles the scrambled content to the clear format. The de-scrambler  410  performs descrambling or de-cryption using a local key provided by the key generator  420 . 
   The key generator  420  receives a user key provided by the user or the content provider and generates the local key to the de-scrambler  410 . The key generator  420  may be an interface circuit to interface to a communication channel to receive the user key downloaded from system at the site of the service provider or transferred from another or master CA unit. 
   According to one embodiment of the invention, the user obtains the user key from the service provider to have access to the scrambled content. The user key is programmable. The user is also granted a right to use the user key in multiple CA devices within his or her control. The granting of this right can be manifested by an authorization code. 
   The user can copy or re-generate the user key in a number of ways. In one embodiment, the user key is transferred from a master CA device to a second CA device by establishing a connection between the master and the second CA devices. In a second CA device, the key generator  420  has an interface to a connection port via line  422  to receive the user key transferred from a master CA device. In a master CA device, the key generator  420  therefore has an interface to a connection port via line  424  so that the user key can be re-generated for transfer to a second CA device. The transfer of the user key from a master CA device or from a user key transmitter (e.g., directly from the service provider) is permitted only if the receiving unit (e.g., the second CA device) has a proper authorization code. The user therefore can transfer his or her user key to any CA device under his or her control according to the right granted as provided by the authorization code. 
   The communication interface  430  provides the authorization code to the key generator  420  to allow the generation of the local key. The communication interface  430  receives the authorization code via a communication channel. The communication channel may be a return path of a cable connection, a telephone connection, or a network. The communication interface  430  may be a modem connection to connect directly to the service provider site. The authorization code may be obtained at the time a contract for service is executed between the user and the service provider, or subsequently when the user contacts the service provider for authorization. Alternatively, the user may register to the service provider as a registered owner of the CA device that has the right to access the scrambled content. Subsequently, the authorization code can be provided to the user if evidence of registered ownership is verified. 
   In one embodiment, the content may be embodied in a medium. The authorization code may accompany the medium at the time of purchase with a specified grant of right. In another embodiment, the authorization code may be entered directly by the user after contacting the service provider to obtain the authorization code. The user key may also be embedded in the medium embodying the scrambled digital content. 
     FIG. 5  is a flowchart illustrating a process  500  for copy protection for a master CA device according to one embodiment of the invention. 
   Upon START, the process  500  receives a user key from the content provider (Block  510 ). The user key may be provided by any means. Then, the process  500  receives an authorization code from the content provider (Block  515 ). The authorization code grants the user a right to duplicate the user key for use in other CA devices. 
   Next, the process  500  establishes a connection with a second CA device (Block  520 ). The connection may be established via any means including electrical connections with connection ports configured for the transfer. Then, the process  500  transfers the user key and optionally the authorization code to the second CA device (Block  530 ). In one embodiment, the transfer is permitted when the authorization code matches the authorization code stored in the second CA device. Then the process  500  is terminated. 
     FIG. 6  is a flowchart illustrating a process  600  for copy protection for a second CA device according to one embodiment of the invention. 
   Upon START, the process  600  receives an authorization code via a communication channel (Block  610 ). The authorization code may be obtained by the user via any means. The authorization code may be entered by the user as instructed by the content provider at the time a contract between the user and the content provider is executed. Then the process  600  establishes a connection with a master CA device or a user key transmitter (Block  620 ). The master CA device is a device that originally has a user key unique to the user. The user key transmitter may be any mechanism that can transfer the user key to the second device. Then, the process  600  receives the user key from the master CA device or the user key transmitter (Block  630 ). In one embodiment, the receipt of the user key is permitted only if the authorization code in the second CA device matches the authorization code in the master CA device or in the user key transmitter. 
   Next, the process  600  generates a local key from the received user key using the authorization code (Block  640 ). The local key as generated has the same effect as the original user key. Then, the process  600  de-scrambles the scrambled content using the local key (Block  650 ). The process  600  is then terminated. 
   While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, which are apparent to persons skilled in the art to which the invention pertains are deemed to lie within the spirit and scope of the invention.