Patent Publication Number: US-7594110-B2

Title: System and method for protecting transport stream content

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 10/153,338, filed May 22, 2002 now U.S. Pat. No. 7,058,803. The above-identified application is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to systems and methods that protect transport stream content and, more specifically, to systems and methods that protect unscrambled transport stream content. 
     BACKGROUND OF THE INVENTION 
     A receiver and, in particular, a set top box generally receives information signals that have been scrambled and information signals that have not been scrambled (i.e., clear information signals). An example of a clear information signal is a network television broadcast signal. Current laws and regulations may prohibit the scrambling of network television broadcast signals. Accordingly, there is a risk that the network television broadcast signal which is received by the set top box may be stored or re-routed outside of the set top box, resulting in possibly unauthorized broadcasting, streaming or copying of the network television broadcast signals. 
     What is needed is a system or a method that protects transport stream content, even transport stream content that has not been scrambled. 
     SUMMARY OF THE INVENTION 
     The present invention may provide systems and methods that protect transport stream content. The system may include a first module and a second module, the first module having a common interface. The second module is coupled to the first module via the common interface. The first module demodulates an incoming transport stream, copy protection encrypts the demodulated transport stream and passes the copy protection encrypted transport stream to the second module via the common interface. The second module copy protection decrypts the transport stream received from the first module, conditional access decrypts at least some of packets of the transport stream that were conditional access encrypted, copy protection encrypts the transport stream and passes the copy protection encrypted transport stream to the first module via the common interface. 
     The present invention may also provide systems and methods that protect transport stream content. The system may include a first module and a second module, the first module having a common interface. The second module is coupled to the first module via the common interface. The first module demodulates an incoming transport stream, copy protection encrypts packets of the demodulated transport stream that were not conditional access encrypted and passes the copy protection encrypted packets and the conditional access encrypted packets of the transport stream to the second module via the common interface. The second module conditional access decrypts at least some of the packets of the transport stream that were conditional access encrypted, copy protection encrypts the packets of the transport stream that were conditional access decrypted and passes the transport stream to the first module via the common interface. 
     The present invention may provide an advantage in that packets of the transport stream that pass through the common interface, which may be user accessible, are either copy protection encrypted or conditional access encrypted. Thus, a user could not tap or re-route, via the common interface, packets that were not encrypted. 
     These and other features and advantages of the present invention may be appreciated from a review of the following detailed description of the present invention, along with the accompanying figures in which like reference numerals refer to like parts throughout. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a block representation of an example of a conditional access system according to the present invention. 
         FIG. 2  shows a block representation of an example of a conditional access card according to the present invention. 
         FIG. 3  shows a flowchart illustrating an example of a method that protects a transport stream according to the present invention. 
         FIG. 4  shows a block representation of another example of a conditional access card according to the present invention. 
         FIG. 5  shows a flowchart illustrating another example of a method that protects a transport stream according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a block representation of an example of a conditional access system  100  according to the present invention. The conditional access system  100  may include, for example, a head-end module  110  and a receiver module  120 . The head-end module  110  is coupled to the receiver module  120  via a communication media that is wired (e.g., cables, landline networks, terrestrial networks, etc.); wireless (e.g., satellite signals, radio frequency (RF) signals, cellular signals, personal communications services (PCS) signals, infrared (IR) signals, etc.); or some combination thereof. 
     The receiver module  120  may comprise, for example, a set top box  130 . The set top box  130  may include, for example, a demodulator  140 , a copy protection encryption unit  150 , a common interface  160 , a conditional access card  170  and a transport processor  180 . The set top box  130  may include other components that are not shown or described here but are known to one of ordinary skill in the art. In addition, the set top box  130  may be coupled to an output device (e.g., a display, a screen, a monitor, a storage device, a printer, etc.) or other devices that are also known to one of ordinary skill in the art. 
     The head-end module  110  is coupled to the demodulator  140  of the set top box  130 . The demodulator  140  is coupled to the copy protection encryption unit  150 . The copy protection encryption unit  150  is coupled to the conditional access card  170  via the common interface  160 . The conditional access card  170  is coupled to the transport processor  180  via the common interface  160 . The present invention contemplates that the common interface  160  may be integrated, at least in part, with one or more of the above-described components or may be a separate module. 
     The conditional access card  170  may be, for example, a personal computer memory card international association (PCMCIA) card, a smart card, an interface card or a printed circuit board, that is plugged into, mounted on or integrated with the set top box  130  via the common interface  160  which may be accessible by the user or the subscriber. In particular, the conditional access card  170  may be, for example, a common interface card or a point of deployment (POD) module. 
     In operation, the head-end module  110 , for example, managed by the content provider, may provide content to, for example, subscribers located at the receiver module  120 . The content may be scrambled via, for example, a conditional access encryption unit of the head-end module  110 , to protect against unauthorized access (e.g., by a non-subscriber, by a limited-access subscriber, etc.) However, federal laws may prohibit the content provider from scrambling all content provided to the receiver module  120 . For example, federal laws may prohibit the scrambling of network television broadcast signals. Accordingly, the transport stream provided by the head-end module  110  to the receiver module  120  may include scrambled packets and unscrambled packets (i.e., clear packets). The transport stream is modulated and sent to the receiver module  120 . The demodulator  140  of the set top box  130  demodulates the received transport stream and forwards the demodulated transport stream to the copy protection encryption unit  150 . 
     In one embodiment, the present invention provides that the copy protection encryption unit  150  copy protection encrypts the entire demodulated transport stream. The copy encrypted transport stream is then sent to the conditional access card  170  via the common interface  160 . The conditional access card  170  copy protection decrypts the entire demodulated transport stream and unscrambles the scrambled packets of the copy protection decrypted transport stream. The conditional access card  170  may unscramble all of the scrambled packets or may unscramble some of the scrambled packets (e.g., unscramble only those packets associated with a particular premium movie channel). The conditional access card  170  then copy protection encrypts the entire transport stream before sending the copy protection encrypted transported stream to the transport processor  180  via the common interface  160 . The transport processor  180  may then copy protection decrypt the received transport stream before processing the transport stream. The further processing of the transport stream in the set top box  130  is known to one of ordinary skill in the art and is not described further herein. 
     In another embodiment, the present invention provides that the copy protection encryption unit  150  copy protection encrypts the clear packets within the demodulated transport stream. Whether a packet is clear or scrambled can be determined, for example, by a bit in a header portion of the packet. The transport stream, including copy protection encrypted packets and scrambled packets, is then sent to the conditional access card  170  via the common interface  160 . The conditional access card  170  unscrambles the scrambled packets of the received transport stream. As described above, the conditional access card  170  may unscramble all of the scrambled packets or may unscramble some of the scrambled packets. The conditional access card  170  then copy protection encrypts the unscrambled packets of the transport stream before sending the copy protection encrypted transport stream to the transport processor  180  via the common interface  160 . The transport processor  180  may then copy protection decrypt the copy protection encrypted packets of the received transport stream before processing the transport stream. As described above, the further processing of the transport stream in the set top box  130  is known to one of ordinary skill in the art and is not described further herein. 
     In the above-described embodiments, the present invention may provide that the packets of the transport stream that pass through the common interface  160  are either scrambled or copy protection encrypted. Thus, although the common interface  160  may be user accessible, a user could not obtain any clear or unscrambled packets at the common interface  160  and potentially tap or re-route the clear or unscrambled packets to a destination outside the set top box  130  resulting in, for example, unauthorized broadcasting, streaming or copying of clear or unscrambled packets of the transport stream. 
       FIG. 2  shows a block representation of an example of the conditional access card  170  according to the present invention. The conditional access card  170  may include, for example, a copy protection decryption unit  190 , a conditional access decryption unit  200 , and a copy protection encryption unit  210 . The copy protection decryption unit  190  is coupled to the conditional access unit  200  which, in turn, is coupled to the copy protection encryption unit  210 . 
       FIG. 3  shows a flowchart illustrating an example of a method that protects a transport content stream according to the present invention. Referring to  FIGS. 1-3 , the process begins, in step  220 , by demodulating the transport stream received by the demodulator  140  of the receiver module  120  from the head-end module  110 . The demodulated transport stream is sent to the copy protection encryption unit  150 . In step  230 , the copy protection encryption unit  150  encrypts the entire demodulated transport stream and, in step  240 , sends the copy protection encrypted transport stream to the conditional access card  170  via the common interface  160 . In step  250 , the copy protection decryption unit  190  of the conditional access card  170  copy protection decrypts the entire encrypted transport stream. In step  260 , the conditional access decryption unit  200  decrypts (i.e., unscrambles) the conditional access encrypted packets (i.e., the scrambled packets) of the copy protection decrypted transport stream. The conditional access decryption unit  200  may unscramble all of the scrambled packets or may unscramble some of the scrambled packets (e.g., unscramble only those packets associated with a particular channel). In step  270 , the copy protection encryption unit  210  then copy protection encrypts the entire transport stream before, in step  280 , sending the copy protection encrypted transported stream to the transport processor  180  via the common interface  160 . In step  290 , the transport processor  180  then copy protection decrypts the received transport stream before processing the transport stream in step  300 . Alternatively, step  290  may be performed by a separate copy protection decryption unit (not shown). 
       FIG. 4  shows a block representation of another example of the conditional access card  170  according to the present invention. The conditional access card  170  may include, for example, the conditional access decryption unit  200  coupled to the copy protection encryption unit  210 . 
       FIG. 5  shows a flowchart illustrating another example of a method that protects a transport content stream according to the present invention. Referring to  FIGS. 1 ,  4  and  5 , the process begins, in step  310 , by demodulating the transport stream received by the demodulator  140  of the receiver module  120  from the head-end module  110 . In step  320 , the copy protection encryption unit  150  copy protection encrypts the clear packets within the demodulated transport stream. In step  330 , the transport stream, including copy protection encrypted packets and scrambled packets. is then sent to the conditional access card  170  via the common interface. In step  340 , the conditional access decryption unit  200  decrypts (i.e., unscrambles) the conditional access encrypted packets (i.e., the scrambled packets) of the copy protection decrypted transport stream. The conditional access decryption unit  200  may unscramble all of the scrambled packets or may unscramble some of the scrambled packets. In step  350 , the copy protection encryption unit  210  then copy protection encrypts the unscrambled packets (e.g., the scrambled packets that were unscrambled by the conditional access decryption unit  200 ) of the transport stream, before, in step  360 , sending the copy protection encrypted transport stream to the transport processor  180  via the common interface  160 . In step  370 , the transport processor  180  then copy protection decrypts the copy protection encrypted packets of the received transport stream before, in step  380 , processing the transport stream. 
     It is contemplated that any known conditional access and copy protection encryption schemes may be used in connection with the various embodiments of the present invention. 
     While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted, without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiments disclosed, but that the present invention include all embodiments falling within the scope of the appended claims.