Patent Publication Number: US-7917960-B2

Title: Transmitter, signal transfer method, data distribution system and method of same, data receiver, data provider and method of same, and data transferer

Description:
This is a continuation of U.S. application Ser. No. 11/319,857, filed Dec. 28, 2005, which is a divisional of U.S. application Ser. No. 09/980,057, filed Mar. 13, 2002 under 35 USC 371, now U.S. Pat. No. 7,418,735, based on International Application PCT/JP01/02807, with a claim of priority to Japanese Applications 2000-102246, filed in Japan on Apr. 4, 2000, and 2000-149848, filed in Japan on May 17, 2000, all of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a transmitter, signal transfer method, data distribution system and method of same, data receiver, data provider and method of same, and data transferee. More specifically, the present invention relates to a technology for holding in advance information indicating a receiver which does not have the function of being able to copy content using a transferred content signal, and controlling the transfer of a content signal of content or a copyright protected content signal according to whether or not information indicating a connected receiver is included in the held information at the time of transfer of the content. 
     BACKGROUND ART 
     In the past, a computer system etc. has converted a digital image signal to an analog image signal and supplied the same to a display device by analog transmission. However, along with the spread of display devices for driving displays by using a digital signal, for example, liquid crystal displays, the method of digitally transferring a digital image signal without converting the same to an analog signal for preventing degradation of the quality of the image or reducing costs has been standardized. For example, the DDWG (Digital Display Working Group) is formulating a DVI (Digital Visual Interface, Version 1.0) specification. This DVI specification uses a TMDS (transition minimized differential signal) channel developed by Silicon Image Corp. of the U.S. to serially transfer a digital three-primary color image signal by the baseband for every color. 
       FIG. 4  is a conceptual view of a signal transfer system for transferring a digital image signal of content by using a channel of the DVI specification. A transmitter (for example a computer system or set top box)  20  for transmitting the image signal and a receiver (display device, television system, etc.)  50  for receiving the image signal and displaying the image are connected via channels  30  of the DVI specification. In a DVI specification channel, not only is a TMDS channel for transferring a digital image signal used as mentioned above, but also a bi-directional channel (I 2 C bus or the like) used for information transfer in a DDC (display data channel) specification relating to plug and play established by VESA (Video Electronics Standard Association) is provided. 
     Here, if a transmission controller  25  of the transmitter  20  detects that the receiver  50  has been connected, the transmission controller  25  communicates with a reception controller  53  of the receiver  50  according to the DDC protocol, controls an image signal generator  21  based on receiver information obtained from the reception controller  53 , for example, information of a model name and resolution of the receiver  50 , and generates a digital three-primary color image signal optimum for the receiver  50 . The three-primary color image signal DG is supplied to a transmission processor  22  comprised by using a TMDS transmission circuit. The transmission processor  22  generates a baseband serial transfer signal SD from the supplied three-primary color image signal DG and supplies it to the receiver  50  from a connector  27  via the channel  30 . The receiver  50  supplies the serial transfer signal SD supplied via a connector  51  to a reception processor  52 . The reception processor  52  is comprised by using a TMDS reception circuit and generates the digital three-primary color image signal DS from the serial transfer signal SD and supplies it to an image display  54 . For this reason, the image display  54  can optimize and display an image of the content based on the three-primary color image signal DS. 
     Since the content transferred via the channel  30  of TMDS is converted to the digital signal, a perfect copy can be prepared easily and limitlessly. This is a great advantage for the user, but a problem in terms of protecting the rights of the side providing a movie or Other work. For this reason, a proposal referred to as “DVI-CP (Content Protection)” using encryption technology for copyright protection when transferring a digital signal of content by using a DVI specification channel has been made by Intel Corporation of the U.S. 
       FIG. 5  is a conceptual view of a signal transfer system for transferring a signal of content compatible with the DVI-CP specification. The image signal generator  21  of a transmitter  20   a  has a protection information detector  23  connected to it. This protection information detector  23  decides the digital three-primary color image signal DG to be transferred includes protection information indicating that the signal is one of content to be copyright protected. When this protection information detector  23  detects the protection information (when it is decided that the content is to be copyright protected), an encryption circuit  221  provided in a transmission processor  22   a  encrypts the three-primary color image signal DG and provides this encrypted signal, that is, the three-primary color image signal DGE, to the TMDS signal circuit  222 , to generate the serial transfer signal SD. 
     Also, a reception processor  52   a  of a receiver  50   a  is comprised by using not only a TMDS reception circuit  521 , but also a decryption circuit  522 . The TMDS reception circuit  521  receives the serial transfer signal SD, generates a three-primary color image signal, and supplies it to the decryption circuit  522  for the decryption processing. Here, a transmission controller  25   a  of the transmitter  20   a  and a reception controller  53   a  of the receiver  50   a  perform processing for mutual authentication according to the DDC protocol and, when deciding that a correct party is connected, supply the encryption key DC used for the encryption of the three-primary color image signal DG to the decryption circuit  522  to enable the decryption circuit  522  to correctly decrypt the encrypted three-primary color image signal. The digital three-primary color image signal DG obtained at this decryption circuit  522  is supplied to the image display  54 . Even if the three-primary color image signal DG is transferred encrypted, the image of content can be correctly optimized and displayed on an image display  3 . 
     Also, since the serial transfer signal SD is generated based on the encrypted three-primary color image signal DGE, the unencrypted three-primary color image signal DS cannot be obtained just by receiving the serial transfer signal SD, so the content can be prevented from being digitally copied as it is. 
     If, however, encryption technology for copyright protection is added to this DVI specification and becomes standard after use of receivers  50  based on the above DVI specification starts, when a transmitter  20   a  based on the new specification encrypts and outputs a digital image signal, a prior DVI specification receiver  50  sometimes will not be able to display the image since it does not have the function of decrypting an encrypted digital image signal. 
     For example, as shown in  FIG. 6 , when outputting a digital image signal from a transmitter  20  based on the conventional DVI specification as a serial transfer signal SD, both a receiver  50  based on the conventional DVI specification or a receiver  50   a  based on the new specification including the encryption technology can display the image of the content. Also, when outputting a digital image signal from a transmitter  20   a  based on the new specification including the encryption technology as the serial transfer signal SD, a receiver  50   a  having the function of decrypting an encrypted digital image signal can display the image of the content. Since the receiver  50  does not have a decryption function however, sometimes the receiver  50  cannot be used for copying content without inviting degradation of the quality of the image etc., for example, it does not have the function of outputting the supplied digital three-primary color image signal or converting the three-primary color image signal to for example an NTSC system video signal for output and therefore cannot display the image of the content even if it is clear that copyright protection is possible. 
     DISCLOSURE OF THE INVENTION 
     An object of the present invention is to provide a transmitter and a signal transfer method enabling correct display of an image even if a transmitter for a digital image signal designed for a digital transfer method incorporating encryption technology for copyright protection is connected with a receiver designed for a digital transfer method not incorporating encryption technology for copyright protection. 
     Another object of the present invention is to provide a data distribution system and a data distribution method enabling a content owner to directly control copying as desired while using a standard apparatus as a processor after the receiver. 
     Still another object of the present invention is to provide a data receiver used in such a content distribution system, receiving the distributed content data, performing adequate right processing, and outputting the content data in a usable manner. 
     Still another object of the present invention is to provide a data provider and a data providing method for providing content data to be distributed in a state where the owner of the content can control the usage thereof. 
     Still another object of the present invention is to provide a data transferer for transferring the data provided in this way. 
     Accordingly, a transmitter according to the present invention comprises a transmission processing means for transferring a content signal or processing copyright protection to a content signal and then transferring the processed content signal and a transmission controlling means for holding information indicating a receiver which does not have a function enabling copying of content by using the content signal the processed content signal transferred from the transmission processing means and controlling output of the signal to be transferred from the transmission processing means according to whether or not information indicating the receiver which is connected to the transmission processing means is included in the held information. 
     A signal transfer method according to the present invention includes the steps of holding in a transmitter information indicating receivers not having the function of being able to receive a content signal to copy the content and controlling the output of the content signal or content signal after provided with copyright protection at the transmitter according to whether or not information indicating a connected receiver is included in the held information. 
     In the present invention, when for example the model names of receivers not having the function of being able to use a transferred content signal to copy the content are held in a transmitter in advance and the model name of a connected receiver is included in the held model names, a non-copyright protected content signal is transferred from the transmitter to the receiver regardless of whether or not the content to be transferred is copyright protected. Also, when a change of the receiver is detected by a hot plug detection function or a plug and play function while transferring a content signal of copyright protected content without providing copyright protection, the transfer of the non-copyright protected content signal is suspended or a copyright protected content signal is transferred instead of the non-copyright protected content signal. Also, the transmitter holds the model name or other information indicating the receiver in a tamper-proof updateable manner. 
     A data distribution system according to the present invention comprises a data providing means for adding first control information for controlling a usage state of the content data to the intended content data and providing the result as the data to be distributed, a data transmitting means for performing predetermined second encryption on the provided data to be distributed and transmitting the encrypted data to be distributed, and a data receiving means for receiving the transmitted encrypted data to be distributed, performing decryption of the second encryption, detecting the first control  15  information from the decrypted data to be distributed, and controlling the output of the content data based on the detected first control information. 
     Preferably, the data providing means superimposes the first control information as electronic watermark information on the content data and provides the superimposed content data as the data to be distributed to the data transmitting means, the data transmitting means performs the predetermined second encryption on the provided data to be distributed and transmits the encrypted data to be distributed, and the data receiving means receives the transmitted encrypted data to be distributed, performs the decryption of the second encryption, detects the superimposed first control information from the decrypted data to be distributed, and controls the output of the content data based on the detected first control information. 
     More preferably, the data providing means performs predetermined first encryption on the content data with the first control information superimposed thereon as the electronic watermark information and provides the encrypted data as the data to be distributed to the data transmitting means, the data transmitting means performs the second encryption for the provided data to be distributed and transmits the encrypted data to be distributed, and the data receiving means receives the transmitted encrypted data to be distributed, performs the decryption of the second encryption, generates the content data with the electronic watermark information superimposed thereon by performing the decryption of the first encryption, detects the superimposed first control information from the generated content data, and controls the output of the content data based on the detected information. 
     Specifically, the data transmitting means adds second control information for controlling a usage state of the content data to the provided data to be distributed, performs the second encryption on the data to be distributed with the second control information added thereto, and transmits the encrypted data to be distributed, the data receiving means receives the transmitted encrypted data to be distributed, performs the decryption of the second encryption, detects the second control information, generates the content data with the electronic watermark information superimposed thereon by performing the decryption of the first encryption for the decrypted data to be distributed, detects the first control information superimposed as the electronic watermark information from the generated content data, and controls the output of the content data based on the detected first control information and second control information. 
     More specifically, the data providing means adds a control descriptor indicating the first control information to the content data and provides the content data with the control descriptor added thereto as the data to be distributed to the data transmitting means, the data transmitting means performs the predetermined second encryption for the provided data to be distributed and transmits the encrypted data to be distributed, and the data receiving means receives the transmitted encrypted data to be distributed, performs the decryption of the second encryption, detects the added first control information from the decrypted data to be distributed, and controls the output of the content data based on the detected first control information. 
     Preferably, the data transmitting means adds second control information for controlling a usage state of the content data to the provided data to be distributed, performs the second encryption for the data to be distributed with the second control information added thereto, and transmits the encrypted data to be distributed, and the data receiving means receives the transmitted encrypted data to be distributed, performs the decryption of the second encryption, detects the second information, performs the decryption of the first encryption for the decrypted data to be distributed to generate content data with the control descriptor added thereto, detects the first control information added as the control descriptor from the generated content data, and controls the output of the content data based on the detected first control information and second control information. 
     Preferably, the data providing means superimposes third control information for controlling a usage state of the signal when outputting the content data by an analog signal on the content data as the electronic watermark information and provides the content data with the third control information superimposed thereon as the data to be distributed, the data transmitting means performs the predetermined second encryption for the provided data to be distributed, transmits the encrypted data to be distributed, and the data receiving means receives the transmitted encrypted data to be distributed, performs the decryption of the second encryption, and outputs the signal with the decrypted the third control information superimposed thereon as the electronic watermark information as the analog signal output in response to a request. 
     Preferably, the data receiving means further has a memory means for storing information concerning charging with respect to a usage of the content data based on a usage state of the received content data. 
     A data distribution method according to the present invention comprises the steps of adding first control information for controlling a usage state of content data to intended content data based on an instruction of an owner of the content data and providing the result as the data to be distributed, performing predetermined second encryption on the provided data to be distributed, transmitting the encrypted data to be distributed, receiving the transmitted encrypted data to be distributed at any receiver, performing the decryption of the second encryption, detecting the first control information from the decrypted data to be distributed, and controlling the output of the content data based on the detected first control information. 
     A data receiver according to the present invention is a data receiver for receiving a signal comprised of data to be distributed including intended content data plus first control information for controlling a usage state of the content data and transmitted after performing predetermined second encryption, comprising a receiving means for receiving the transmitted signal, a second decrypting means for performing decryption of the second encryption with respect to the received signal, a first control information detecting means for detecting the first control information from the decrypted data to be distributed, and an output controlling means for controlling the output of the content data based on the detected first control information. 
     A data provider according to the present invention has a control information adding means for adding control information for controlling a usage state of content data designated by an owner of the content data to intended content data and provides the content data with the control information added thereto as data to be distributed. 
     A data providing method according to the present invention comprises the steps of adding control information for controlling a usage state of content data designated by an owner of content data to intended content data, encrypting the content data with the control information added thereto by a predetermined method, and providing the encrypted content data as the data to be distributed. 
     A data transferer according to the present invention comprises an encrypting means for further encrypting, by a predetermined method, data to be distributed including intended content data plus control information for controlling a usage state of the content data designated by an owner of the content data and encrypted by a predetermined scheme and a transferring means for transferring the encrypted data to be distributed to any channel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objects and features of the present invention will become more apparent from the following description given with reference to the accompanying drawings, wherein: 
         FIG. 1  is a conceptual view of a signal transfer system according to the present invention, 
         FIG. 2  is a view of a pin arrangement of a connector of the DVI specification, 
         FIG. 3  is a flowchart of an operation of a transmitter, 
         FIG. 4  is a conceptual view of a signal transfer system of the DVI specification, 
         FIG. 5  is a conceptual view of a signal transfer system designed for the DVI-CP specification, 
         FIG. 6  is a view of compatibility of hardware based on the DVI specification and hardware based on the DVI-CP specification, 
         FIG. 7  is a view of an overall schematic configuration of a content distribution system of a second embodiment of the present invention, 
         FIG. 8  is a view of the configuration of a principal part of a first concrete example of the content distribution system shown in  FIG. 7 , 
         FIG. 9  is a view of the configuration of a principal part of a second concrete example of the content distribution system shown in  FIG. 7 , 
         FIG. 10  is a view of the configuration of a principal part of a third concrete example of the content distribution system shown in  FIG. 7 , 
         FIG. 11  is a flowchart for explaining decision processing in a decision controller of a set top box shown in  FIG. 10 , 
         FIG. 12  is a view of the configuration of a principal part of a fourth concrete example of the content distribution system shown in  FIG. 7 , 
         FIG. 13  is a flowchart for explaining the decision processing in the decision controller of the set top box shown in  FIG. 12 , 
         FIG. 14  is a view of the configuration of a principal part of a fifth concrete example of the content distribution system shown in  FIG. 7 , and 
         FIG. 15  is a view of the configuration of a principal part of a sixth concrete example of the content distribution system shown in  FIG. 7 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Preferred embodiments of the present invention will be explained next referring to the attached drawings. 
     First Embodiment 
     Below, an explanation will be made of a first embodiment of the present invention by referring to the drawings. 
       FIG. 1  is a conceptual view of a signal transfer system for transferring a digital image signal of content. A transmitter (for example a computer system or set top box)  10  for transmitting the image signal and a receiver (display device, television set, etc.)  40  for receiving the image signal and displaying the image are connected via DVI specification channels  30 . The DVI specification channels  30  are provided with a TMDS channel for transferring the digital image signal, a bi-directional channel used for DDC (display data channel) specification information transfer relating to plug and play established by the VESA (Video Electronics Standard Association), a power supply line, and a hot plug detection use signal line. 
       FIG. 2  is a view of a pin arrangement of a DVI specification connector. Note that the figure shows the case where a channel for transferring an analog image signal is provided. Pins “ 1 ” to “ 5 ”, “ 9 ” to “ 13 ”, and “ 17 ” to “ 24 ” are for TMDS channels, pins “ 6 ” and “ 7 ” are for DDC use bi-directional channels (I 2 C bus), and pins “C 1 ” to “C 5 ” are for channels for analog image signals. Further, pins “ 14 ” and “ 15 ” are for a 5V power supply line and a ground line, and a pin “ 16 ” is defined as for a hot plug detection use signal line. 
     An image signal generator  11  of the transmitter  10  shown in  FIG. 1  generates a three-primary color image signal DG of the content by a resolution and number of colors optimum with respect to the receiver  40  based on a signal generation control signal GC supplied from a DDC protocol processing circuit  152  mentioned later and supplies the same to an encryption circuit  121  of a transmission processor  12 , a terminal a of a signal selection circuit  122 , and a protection information detector  13 . 
     The encryption circuit  121  of the transmission processor  12  encrypts the three-primary color image signal DG by for example an encryption key KC and supplies it as the three-primary color image signal DGE to a terminal b of the signal selection circuit  122 . A moveable terminal c of the signal selection circuit  122  is connected to one terminal of the output control switch  123 , is controlled by a protection operation control signal PT supplied from a authentication processing circuit  151  of a transmission controller  15  mentioned later, and selects either of the non-encrypted three-primary color image signal DG supplied to the terminal a or the encrypted three-primary color image signal DGE supplied to the terminal b. 
     The other terminal of the output control switch  123  is connected to a TMDS transmission circuit  124 . The on/off operation of this output control switch  123  is also controlled by a protection operation control signal PU from the authentication processing circuit  151 . 
     The TMDS transmission circuit  124  encodes the three-primary color image signal selected at the signal selection circuit  122  and supplied via the output control switch  123 , tries to balance a DC level and minimize the number of times of inversion of the logic level, and converts the signal to a baseband serial transfer signal SD suitable for transfer. The serial transfer signal SD for each color is output from a connector  17  to a channel  30 . Note that a horizontal synchronization signal and a vertical synchronization signal of the three-primary color image signal DG are inserted in a blanking period of for example a blue image signal and transmitted. 
     The protection information detector  13  detects whether to provide copyright protection according to the copyright protection information of the three-primary color image signal DG and supplies a decision signal PD to the authentication processing circuit  151 . As this copyright protection information, use is made of CGMS (copy generation management system) information indicating if the content can be freely copied or copying is prohibited or whether to recognize only one copy or CCI (copy control information) etc. Also, when an analog image signal is supplied to the image signal generator  11  and this analog image signal is transferred converted to a digital signal, it is also possible to decide whether or not to provide copy protection based on an APS (analog protection system) signal for copyright protection used in the analog image signal. 
     The authentication processing circuit  151  of the transmission controller  15  is comprised using an electrically programmable nonvolatile memory. This authentication processing circuit  151  registers in it classification information of receivers to be connected to the transmitter  10 , for example, the model names of the receivers. As the classification information registered in this authentication processing circuit  151 , classification information indicating the receivers not having a function for copying the content without inviting degradation of the quality of image etc., for example, classification information indicating the receivers not having a function for outputting the supplied digital image signal or converting the digital image signal to for example an NTSC system video signal and outputting the same is registered. Also, the authentication processing circuit  151  decides whether or not the model name of the receiver indicated by hardware information RR supplied from the DDC protocol processing circuit  152  mentioned later is registered and generates the protection operation control signals PT and PU and supplies them to the transmission processor  12  based on this decision result and the decision signal PD supplied from the protection information detector  13 . 
     The DDC protocol processing circuit  152  communicates with the receiver  40  via the connector  17  and the channels  30  in accordance with the DDC protocol and supplies the hardware information RR supplied from the receiver  40  to the authentication processing circuit  151 . Also, the DDC protocol processing circuit  152  performs the authentication processing with the connected receiver  40  based on the decision result at the protection information detector  13  so as to decide whether or not the connected receiver  40  is based on the new specification including the encryption technology for copyright protection. Here, when it is confirmed that the receiver  40  is based on the new specification, the circuit performs processing for supplying the encryption key KC used when encrypting the three-primary color image signal DG to the receiver  40 . Note that the encryption key KC may be held in the DDC protocol processing circuit  152 , may be supplied from the DDC protocol processing circuit  152  to the encryption circuit  121 , or may be read out by the DDC protocol processing circuit  152  from the encryption circuit  121  when supplying the encryption key KC to the receiver  40 . 
     Further, the DDC protocol processing circuit  152  generates the transfer control signal, TC and supplies the same to the TMDS transmission circuit  124  so as to control the generation and transfer processing of the baseband serial transfer signals SD performed at the TMDS transmission circuit  124 . 
     A connector  41  of the receiver  40  has a reception processor  42  and a reception controller  43  connected to it. The reception processor  42  generates the three-primary color image signal DS based on received serial transfer signal SD and supplies it to a display  44 . When a decryption circuit for decrypting the encrypted three-primary color image signal is provided in the reception processor  42  and the encryption key KC transferred from the transmitter  10  is supplied from the reception controller  43 , the circuit performs the decryption processing of the encrypted three-primary color image signal using this encryption key KC. 
     Next, an explanation will be made of the operation of the transmitter  10  by using the flowchart of  FIG. 3 . At step ST 1 , the transmitter communicates with the connected receiver  40  to obtain the model name, resolution, or other hardware information relating to the receiver  40  and generates a signal generation control signal GC based on this hardware information for supply to the image signal generator  11 . 
     At step ST 2 , it is decided based on the decision signal PD whether or not the content supplied from the transmitter  10  to the receiver  40  is copyright protected. Here, when it is decided based on the decision signal PD from the protection information detector  13  that the content is not copyright protected, the routine proceeds to step ST 3 , where the moveable terminal c of the signal selection circuit  122  is set to the terminal a side by the protection operation control signal PT and the unencrypted three-primary color signal DG is selected, then the routine proceeds to step ST 9 . 
     Also, when it is decided at step ST 2  that the content is copyright protected, the routine proceeds to step ST 4 , where the authentication processing with the receiver  40  is carried out, and it is decided whether or not the connected receiver  40  is based the new specification including the encryption technology for copyright protection. This authentication processing assumes that for example a common key method is utilized, sends the data from the transmitter  10  to the receiver  40 , and encrypts and returns the data by the common key held at the receiver  40 . If this returned encrypted data is inversely converted by the common key and it can be confirmed that the transmitted data appears, it can be correctly decided that the receiver is based on the new specification. Also, if a public key system is utilized, the data is encrypted by the public key of the receiver  40  and sent from the transmitter  10 , the data decrypted by a secret key is returned from the receiver  40 , and it can be confirmed that this returned data is equal to the data which was encrypted and transmitted, it can be correctly decided that the receiver is based on the new specification. 
     When it is decided at step ST 4  that the receiver  40  is based on the new specification, the routine proceeds to step ST 5 , where the encryption key KC used at the encryption circuit  121  is supplied from the DDC protocol processing circuit  152  to the reception controller  43 , then the routine proceeds to step ST 6 . 
     At step ST 6 , the moveable terminal c of the signal selection circuit  122  is set to the terminal b side by the protection operation control signal PT so as to select the encrypted three-primary color image signal DGE, then the routine proceeds to step ST 9 . 
     When it is not decided at step ST 4  that the receiver  40  is based on the new specification, the routine proceeds to step ST 7 , where it is decided whether or not the model name of the receiver  40  indicated by the hardware information RR supplied from the DDC protocol processing circuit  152  is registered in the authentication processing circuit  151 . Here, when it is decided that the model name of the receiver is registered and the receiver does not have a function enabling it to copy content without inviting degradation of the quality of image etc., the routine proceeds to step ST 8 . Also, when it is not registered, the routine proceeds to step ST 10 . 
     At step ST 8 , the moveable terminal c of the signal selection circuit  122  is set to the terminal a side by the protection operation control signal PT so as to select the unencrypted three-primary color image signal DG, then the routine proceeds to step ST 9 . 
     When the routine proceeds from step ST 3  or step ST 6  or step ST 8  to step ST 9 , the output control switch  123  is turned on by the protection operation control signal PU to generate the serial transfer signal SD based on the unencrypted three-primary color image signal DG or the encrypted three-primary color image signal DGE selected at the signal selection circuit  122  and transmit it to the receiver  40 . Also, when the routine proceeds from step ST 7  to step ST 10 , at step ST 10 , the output control switch  123  is turned off by the protection operation control signal PU and the transfer of the serial transfer signal SD based on the three-primary color image signal DG or DGE is prohibited. 
     When copyright protection of the content to be transferred is necessary in this way; when a receiver based on the new specification including encryption technology for copyright protection is connected, the content is transmitted encrypted, so illicit copying of the content can be prevented. Also, even if a receiver  40  not based on the new specification is connected, when it is confirmed that this connected receiver is hardware not having a function of copying the content, the content is transmitted without being encrypted, therefore not only can illicit copying of the content be prevented, but also even a receiver not based on the new specification can be made to correctly display the image of the content. 
     Further, while a digital image signal of content requiring encryption is being transmitted without encryption, it is monitored whether or not there has been a change of connection of the receiver, that is, if the receiver  40  connected to the transmitter  10  has been disconnected or the receiver  40  has been changed. A change of connection of the receiver is monitored by utilizing for example the hot plug detection function or plug and play function. Here, if the hot plug detection function is utilized, it can be decided whether or not the connection of the receiver was changed according to whether or not the receiver was disconnected by the hot plug detection use signal line. Also, if the plug and play function is utilized, it is possible to perform the processing for confirmation of the receiver by the plug and play function even during the transfer of the image signal and therefore decide whether or not there has been a change in connection of the receiver during the transfer of the image signal. 
     When it is decided that there has not been a change in connection during this monitoring of a change of connection of the receiver, the output control switch  123  is held in the on state by the protection operation control signal PU, while when it is decided that there has been a change in connection, the signal selection circuit  122  and the output control switch  123  are controlled by the protection operation control signals PT and PU so that the unencrypted three-primary color image signal DG is not transmitted. For example, by turning the output control switch  123  off by the protection operation control signal PU, the transfer of the unencrypted three-primary color image signal DG can be stopped. Also, by switching the moveable terminal c of the signal selection circuit  122  to the terminal b side by the protection operation control signal PT and selecting the encrypted three-primary color image signal DGE, the unencrypted three-primary color image signal DG can be prevented from being transferred. 
     In this way, even when there is a change in the connection of the receiver while the image signal of the content is being transferred without encryption and, for example, a receiver having a function for copying content without inviting degradation of the quality of image etc. is connected, the unencrypted three-primary color image signal DG is no longer automatically transferred, so the illicit copying of the content can be prevented. 
     The authentication processing circuit  151  is configured using a programmable nonvolatile memory, so new model names can be added to the authentication processing circuit  151 . Here, if the information registered in the authentication processing circuit  151  were tampered with and the model name of a receiver having a function for copying the content without inviting degradation of the quality of image etc. were registered, the content could be illicitly copied. 
     For this reason, the authentication processing circuit  151  uses a means having a high safety so as to prevent the stored information from being tampered with. For example, the hardware is configured so that the information is lost at the time of reverse engineering of the authentication processing circuit  151  or the circuit is configured to make analysis of the information difficult. Also, when updating the stored information, in the same way as the above authentication processing, it is decided whether or not the hardware connected to the transmitter for updating the stored information is correct by utilizing the common key system or the public key system and the update of the stored information is permitted only when it is decided that the apparatus is correct. Further, when the transmitter is hardware such as a set top box, it is also possible to encrypt the information to be updated and supply it to the set top box from the broadcast station side by using the information transmission use channel and have the set top box decrypt the encrypted information by using the secret key stored in an IC card or the like unique to the viewer and update the stored information by using the decrypted information. Also, the transmitter is a computer system. 
     Note that, in the first embodiment, whether or not the content is copyright protected is determined by using a three-primary color image signal DG, but even if information on whether or not the three-primary color image signal DG must be processed for copyright protection is supplied by the image signal generator  11  to the transmission controller  15 , it is possible to similarly operate the transmitter  10 . Further, the signal of the content to be transferred is not limited to an image signal and of course may also be a voice signal. 
     In this way, according to the first embodiment, even if a receiver not based on this new specification is connected to a transmitter based on the new specification including the encryption technology for copyright protection, it is possible to register this receiver not based on the new specification in the transmitter so as to enable a signal output from a transmitter based on the new specification to be received at the receiver not based on the new specification and the content to be used. 
     Second Embodiment 
     Next, the content distribution system and content distribution method enabling a content owner to directly control copying as desired while using a standard apparatus as the processing apparatus after the receiver will be explained as a second embodiment of the present invention by referring to  FIG. 13  to  FIG. 15 . 
     Overall Configuration 
     First, an overall configuration of the content distribution system of the second embodiment will be explained by referring to  FIG. 7 . 
       FIG. 7  is a view of the overall schematic configuration of a content distribution system  1100  of the second embodiment. 
     The content distribution system  1100  has a content owner  1200 , broadcaster  1300 , broadcast network  1400 , set top box  1500 , display device I/F  1600 , and display device  1700 . 
     First, the configuration of each part will be explained. 
     The content owner  1200  is the owner of the content to be distributed, encrypts the content to be distributed by using a desired encryption key Ka, and provides the content in the encrypted state to the broadcaster  1300 . 
     In the present embodiment, the “content” means content including images and sound, for example, TV programs or movies. 
     Note that the “encryption” referred to here broadly means processing the content data itself or any additional data or the like desired by the content owner  1200  to a state preventing it from being changed in any way, read, or used. Accordingly, it specifically includes superimposing additional data in the form of an electronic watermark etc. when actually encrypting content data. Note that, the actual concrete processing content will be explained at the later more concrete explanation of the configuration. 
     The broadcaster  1300  further performs encryption for conditional access by using an encryption key Kb on the content in the encrypted state provided by the content owner  1200  and distributes the same via the broadcast network  1400 . 
     The broadcast network  1400  is any data distributing means including any data distribution system via the communication network going through a communication network such as a digital ground wave broadcast, digital satellite broadcast, CATV, or the Internet and distributes the content data transferred by the broadcaster  1300  to any user. 
     The set top box  1500  is a receiver provided in for example the home of each user and receiving the data transferred by the broadcaster  1300  via the broadcast network  1400  based on an operation of the user. 
     The set top box  1500  decrypts the content data by using the encryption key Ka delivered based on for example a contract in advance when receiving the content data selected by the user. Then, it encrypts the decrypted content data again by using the encryption key Kc set in advance and transfers it to the display device I/F  1600 . In the present embodiment, the set top box  1500  and the display device  1700  are connected using IEEE1394 as the interface, then the set top box  1500  encrypts the content data again by the 5C encryption scheme defined in the IEEE1394. 
     The display device I/F  1600  is a connecting means between the set top box  1500  and the display device  1700  and is the IEEE1394 in the present embodiment as mentioned before. 
     The display device  1700  decrypts the encrypted content data input from the set top box  1500  via the display device I/F  1600  by using the encryption key Kc set in advance and displays the same in a user-viewable manner. 
     Next, the basic overall operation of the content distribution system  1100  having such a configuration will be explained. 
     First, the content to be distributed is encrypted by the owner, that is, the content owner  1200 , by using the encryption key Ka, then transferred to the broadcaster  1300 , then is further encrypted for conditional access by the broadcaster  1300  by using the encryption key Kb and transferred to the broadcast network  1400 . 
     The data transferred to the broadcast network  1400  is specifically substantially received by the viewer (user of the content) selected to be viewed from the set top box  1500  operated by the user and the encryption for the conditional access is first decrypted by an internal decryptor. The encryption key Ka at this time is provided in the form of a secure storage medium such as an IC card when the user concludes a reception contract with the broadcaster  1300  in advance. 
     The decrypted content data is encrypted again by the 5C scheme of the IEEE1394 by using the encryption key Kc set in advance and is transferred to the display device  1700 . 
     Then, it is decrypted at the display device  1700  and displayed in a user viewable manner. 
     Note that the operation performed by the viewer on the set top box  1500  such as the selection of the content data to be received and the transfer of the content data from the set top box  1500  to the display device  1700  is successively stored in the charge information memory in the set top box  1500  and used for the charging accompanying the reception of content. 
     In this way, in the content distribution system  1100 , the content owner  1200  itself substantially encrypts the content to be distributed. The encryption is not decrypted until the set top box  1500  of the user. Accordingly, if the control information for controlling for example the reproduction or copying of the content data on the user side is encrypted and superimposed on the content data, the content owner  1200  itself can control the usage of the content data on the user side. Namely, a change of the usage state, usage conditions, etc. of the content set by the broadcaster  1300  can be prevented regardless of the reason. 
     Also, in the content distribution system  1100 , a standard interface can be used between the set top box  1500  and the display device  1700  while placing the usage of the content within a range of such control of the content owner  1200 . Also, the standard hardware compatible with that interface can be used as the display device  1700 . 
     EXAMPLE OF CONCRETE APPLICATION 
     The basic overall configuration of the content distribution system  1100  according to the present invention was explained above, but an example of a more concrete configuration and concrete form of application will be explained as a first concrete example to fifth concrete example. 
     Note that all of the broadcast network  1400 , display device I/F  1600 , and display device  1700  are standard, therefore, in the following explanation, the illustration of these in the drawings and explanations thereof will be omitted. 
     First Concrete Example 
     A first example of concrete application of the content distribution system  1100  will be explained by referring to  FIG. 8 . 
     As the first concrete example, a system wherein the content owner  1200  superimposes the control information for controlling the usage of the content on the content data in the form of an electronic watermark and distributes the same and wherein the usage of the content data received by the user is controlled by this will be illustrated. 
       FIG. 8  is a view of the configuration of the content owner  1200  to the set top box  1500  of the first concrete configuration of the content distribution system  1100 . 
     In the first concrete configuration shown in  FIG. 8 , the content owner  1200  has an electronic watermark superimposer  1208  which superimposes the copy control information for controlling the usage of the content which becomes valid in the set top box  1500  on the content data in the form of an electronic watermark. 
     Further, the content owner  1200  has an encryptor  1210  which encrypts the content data with the electronic watermark superimposed thereon by using the encryption key Ka. 
     Then, it transfers this encrypted content data to the broadcaster  1300 . 
     The broadcaster  1300  has the encryptor  1302  which further performs encryption for conditional access by using the encryption key Kb on the content data input from the content owner  1200  and transmits the same. 
     The set top box  1500  has a decryptor  1502 , decryptor  1504 , electronic watermark detector  1506 , 5C encryptor  1508 , output switch  1510 , and charge information memory  1524 . 
     The decryptor  1502  decrypts the encrypted signal received from the broadcaster  1300  by using the encryption key Kb. Namely, it decrypts the encryption for the conditional access. The decrypted signal is the signal encrypted by the content owner  1200  and can not yet used. 
     The decryptor  1504  further decrypts the signal decrypted at the decryptor  1502  by using the encryption key Ka and outputs the decrypted signal to the electronic watermark detector  1506 , 5C encryptor  1508 , and the output switch  1510 . The signal decrypted at the decryptor  1504  is the signal obtained by the superimposition of the copy control information on the baseband content data as the electronic watermark. 
     The electronic watermark detector  1506  detects the copy control information superimposed as the electronic watermark from the signal decrypted at the decryptor  1504 , generates the signal for controlling the signal to be output from the set top box  1500 , concretely the signal for controlling the output switch  1510  based on this, and applies the same to the output switch  1510 . 
     The 5C encryptor  1508  encrypts the signal decrypted at the decryptor  1504  by the 5C scheme by using the encryption key Kc and applies the same to the output switch  1510 . 
     The output switch  1510  selects either of the unencrypted content data output from the decryptor  1504  or the content data encrypted at the 5C encryptor  1508  as the output signal from the set top box  1500  based on the control signal applied from the electronic watermark detector  1506  and outputs the same from the set top box  1500 . 
     The charge information memory  1524  detects and stores the information relating to the charge accompanying the usage of the content data by detecting the signal substantially output from the set top box  1500  or monitoring the information input from the display device  1700  via the IEEE1394. The information stored in the charge information memory  1524  is suitably transmitted to a predetermined settlement manager where the charge processing is performed. 
     In such a set top box  1500 , the encryption for the conditional access applied at the decryptor  1502  by the broadcaster  1300  is decrypted, the encryption applied by the content owner  1200  itself is decrypted at the decryptor  1504 , and the copy control information added by the content owner  1200  superimposed as the electronic watermark is detected at the electronic watermark detector  1506  from that decrypted content data. 
     Then, when for example this copy control information describes to output the encrypted content data from the set top box  1500 , the data obtained by encrypting the output from the decryptor  1504  at the 5C encryptor  1508  using the encryption key Kc is selected by the output switch  1510  based on the control signal from the electronic watermark detector  1506  and output from the set top box  1500  to a not illustrated display device. 
     Also, when the copy control information describes that unencrypted content data can be output from the set top box  1500 , the output from the decryptor  1504  is selected by the output switch  1510  based on the control signal from the electronic watermark detector  1506  and output from the set top box  1500 . 
     In this way, in the first concrete example, the content owner  1200  superimposes the copy control information on the content data in the form of the electronic watermark and further performs encryption. The content owner  1200  itself can directly control the output of the reception side without intervention by the broadcaster  1300 . 
     Second Concrete Example 
     A second example of concrete application of the content distribution system  1100  will be explained next by referring to  FIG. 9 . 
     The second concrete example is configured as the first concrete example without the encryptor  1210  of the content owner  1200  and omitting the encryption processing. Also, along with this, the set top box  1500  is also configured omitting the decryptor  1504 . 
     In such a configuration, the content owner  1200  superimposes the copy control information in the form of an electronic watermark at the electronic watermark superimposing unit  1208  and provides the content data in that state to the broadcaster  1300  as it is, that is, without encryption. 
     Then, the broadcaster  1300  performs the encryption for the conditional access on this at the encryptor  1302  and transfers the result. 
     The set top box  1500  receiving the transferred signal decrypts the encryption for conditional access at the decryptor  1502  to directly obtain content data not encrypted in any way, detects the copy control information superimposed as the electronic watermark at the electronic watermark detector  1506 , and controls the output switch  1510  by this. 
     The operations of the 5C encryptor  1508 , output switch  1510 , not illustrated charge information memory, etc. are the same as those of the first concrete example. 
     In this way, the second concrete example omits the encryptor  1210  in the content owner  1200  and the decryptor  1504  of the set top box  1500 , so can simplify the configurations of the devices. 
     In such a configuration, the encryption processing by the encryptor  1210  of the content owner  1200  is eliminated, therefore the content data in the unencrypted state is transferred to the broadcaster  1300 . The output of the set top box  1500 , however, is controlled by the electronic watermark information. Further, the electronic watermark data is superimposed. Therefore, illicit usage can be traced, so the possibility of illicit usage can be said to be low. 
     If such a condition is acceptable, this simple configuration second concrete example is effective. 
     Third Concrete Example 
     An explanation will be made of a third concrete application example of the content distribution system  1100  by referring to  FIG. 10  and  FIG. 11 . 
     The third concrete example is configured by the broadcaster  1300  adding a unique control descriptor separate from that added by the content owner  1200 . 
     Specifically, the processing in the content owner  1200  is the same as the processing of the first concrete example. First the copy control information for controlling the usage of the content which becomes valid in the set top box  1500  is superimposed on the content data in the form of an electronic watermark. Next, the encryptor  1210  encrypts the content data with the electronic watermark superimposed thereon by using the encryption key Ka and transfers this encrypted content data to the broadcaster  1300 . 
     The broadcaster  1300  adds the unique control descriptor to the encrypted content data transferred from the content owner  1200  in a control descriptor adder  1306 , encrypts this in the encryptor  1302  by using the encryption key Kb, and transmits the same. 
     The set top box  1500  receiving this decrypts the encryption for the conditional access performed by the broadcaster  1300  in the decryptor  1502  by using the encryption key Kb. 
     From this decrypted signal, the control descriptor added by the broadcaster  1300  is detected at the control descriptor detector  1512  and output to a decision controller  1514 . 
     Also, the signal decrypted at the decryptor  1502  is further-decrypted at the decryptor  1504  by using the encryption key Ka. 
     The electronic watermark detector  1506  detects the copy control information superimposed in the form of an electronic watermark by the content owner  1200  from this decrypted signal and outputs it to the decision controller  1514 . 
     The decision controller  1514  performs the decision for controlling the usage of the received content data based on the copy control information set by the content owner  1200  and input from the electronic watermark detector  1506  and the control descriptor set by the broadcaster  1300  and input from the control descriptor detector  1512  and controls the output data based on that decision. 
     Here, it is assumed that the copy control information and the control descriptor set to output the content data from each set top box  1500  by either transfer by 5C encryption or by transfer without encryption. In that case, the decision controller  1514  performs a decision according to the flowchart as shown in for example  FIG. 11 . 
     Namely, when the decision is started (step S 10 ), first, the copy control information input from the electronic watermark detector  1506  is referred to so as to judge whether it sets 5C encryption (step S 11 ). When it sets 5C encryption, a control signal for selecting the output of the 5C encryptor  1508  is output to the output switch  1510 , whereby 5C encrypted content data is output from the set top box  1500  (step S 12 ). 
     When the copy control information input from the electronic watermark detector  1506  does not set 5C encryption (step S 11 ), the control descriptor input from the control descriptor detector  1512  is referred to so as to judge whether or not it sets 5C encryption (step S 13 ). Then, when it sets 5C encryption, in the same way as the case where the copy control information sets it, a control signal for selecting the output of the 5C encryptor  1508  is output to the output switch  1510 , whereby 5C encrypted content data is output from the set top box  1500  (step S 12 ). 
     Even when the control descriptor input from the control descriptor detector  1512  does not set 5C encryption (step S 13 ), the decision controller  1514  outputs a control signal for selecting the output from the decryptor  1504  to the output switch  1510  to make the set top box  1500  output the unencrypted content data (step S 14 ). 
     In this way, the third concrete example enables the content owner  1200  and the broadcaster  1300  to independently set control of the usage of the content data. Then, it is possible to freely set which setting should be given priority and what kind of control is to be carried out by changing an algorithm set in the decision controller  1514 . 
     BAy employing the algorithm as shown in for example  FIG. 11 , it is possible to execute the setting of the content owner  1200  with priority over the setting of the broadcaster  1300 . 
     Fourth Concrete Example 
     Next, a fourth example of concrete application of the content distribution system  1100  will be explained by referring to  FIG. 12  and  FIG. 13 . 
     The fourth concrete example is configured similar to the third concrete example, but the copying is controlled by the content owner  1200  not by superimposing an electronic watermark on the content data, but by adding a control descriptor to the content data in the same way as the broadcaster  1300 . 
     Namely, the content owner  1200  adds copy control information for controlling the usage of the content which becomes valid in the set top box  1500  to the content data in the form of a control descriptor (control descriptor  1 ) by a control descriptor adder  1212 . Then, the content data with the control descriptor added thereto is encrypted at the encryptor  1210  by using the encryption key Ka and the encrypted content data is transferred to the broadcaster  1300 . 
     The broadcaster  1300  adds a unique control descriptor (control descriptor  2 ) to the encrypted content data transferred from the content owner  1200  at the control descriptor adder  1306 , encrypts this at the encryptor  1302  by using the encryption key Kb, and transfers the same. 
     The set top box  1500  receiving this decrypts the encryption for the conditional access performed by the broadcaster  1300  at the decryptor  1502  by using the encryption key Kb. A control descriptor  2  detector  1512  detects the control descriptor  2  added by the broadcaster  1300  from this decrypted signal and outputs the result to the decision controller  1514 . 
     The signal decrypted at the decryptor  1502  is further decrypted at the decryptor  1504  by using the encryption key Ka. Then, a control descriptor  1  detector  1516  detects the control descriptor  1  added by the content owner  1200  from this decrypted signal and outputs it to the decision controller  1514 . 
     The decision controller  1514  performs the decision for controlling the usage of the received content data based on the control descriptor  1  set by the content owner  1200  input from the control descriptor  1  detector  1516  and the control descriptor  2  set by the broadcaster  1300  input from the control descriptor  2  detector  1512  and controls the output data based on that decision. 
     Here, it is assumed that the control descriptor  1  and the control descriptor  2  set to output the content data from each set top box  1500  by either transfer by 5C encryption or by transfer without encryption. In that case, the decision controller  1514  performs a decision according to the flowchart as shown in for example  FIG. 13 . 
     Namely, when the decision is started (step S 20 ), first, the control descriptor  1  input from the control descriptor  1  detector  1516  is referred to so as to judge whether it sets 5C encryption (step S 21 ). When it sets 5C encryption, a control signal for selecting the output of the 5C encryptor  1508  is output to the output switch  1510 , whereby 5C encrypted content data is output from the set top box  1500  (step S 22 ). 
     When the control descriptor  1  input from the control descriptor  1  detector  1516  does not set 5C encryption (step S 21 ), the control descriptor  2  input from the control descriptor  2  detector  1512  is referred to so as to judge whether or not it sets 5C encryption (step S 23 ). Then, when it sets 5C encryption, in the same way as the case where the control descriptor  1  sets this, a control signal for selecting the output of the 5C encryptor  1508  is output to the output switch  1510 , whereby 5C encrypted content data is output from the set top box  1500  (step S 22 ). 
     When the control descriptor  2  input from the control descriptor  2  detector  1512  also does not set 5C encryption (step S 23 ), the decision controller  1514  outputs a control signal for selecting the output from the decryptor  1504  to the output switch  1510 , whereby unencrypted content data is output from the set top box  1500  (step S 24 ). 
     In this way, in the fourth concrete example, the content owner  1200  and the broadcaster  1300  can independently set control of the usage of the content data in the form of adding a control descriptor. Further, they can freely set how to give priority to what setting and how to control the same by changing an algorithm set in the decision controller  1514 . 
     Further, by employing the algorithm as shown in for example  FIG. 13 , it is possible to execute the setting of the content owner  1200  with priority over the setting of the broadcaster  1300 . 
     Fifth Concrete Example 
     A fifth example of concrete application of the content distribution system  1100  will be explained next by referring to  FIG. 14 . 
     The fifth concrete example enables suitable control of copying even with respect to analog output from the set top box  1500 . 
     In this case, first, the content owner  1200  superimposes the copy control information desired to be set on the content data in the form of an electronic watermark by the electronic watermark superimposer  1208 . This electronic watermark information is used for the copy protection of the analog output from the set top box  1500 . 
     Further, the content owner  1200  encrypts the content data with the electronic watermark information superimposed thereon at the encryptor  1210  by using the encryption key Ka. The content owner  1200  transfers both this encrypted content data and the previous copy control information to the broadcaster  1300 . 
     The broadcaster  1300  converts the copy control information transferred from the content owner  1200  to the control descriptor, then adds this to the encrypted content data transferred from the content owner  1200  at the control descriptor adder  1306 , encrypts the same at the encryptor  1302  by using the encryption key Kb, and transfers the same. 
     The set top box  1500  receiving this decrypts the encryption for the conditional access performed by the broadcaster  1300  at the decryptor  1502  by using the encryption key Kb. The control descriptor detector  1512  detects the control descriptor added by the broadcaster  1300  from this decrypted signal upon instruction from the content owner  1200  and generates a control signal for controlling the output switch  1510  and applies it to the output switch  1510 . 
     Further, the signal decrypted at the decryptor  1502  is further decrypted at the decryptor  1504  by using the encryption key Ka. This decrypted signal is 5C encrypted at the 5C encryptor  1508  or directly applied to the output switch  1510 . Either is selected at the output switch  1510  and output as the digital output. 
     On the other hand, the signal decrypted at the decryptor  1502  is input to an analog signal encoder  1518 , converted to an analog signal here, and output from the set top box  1500 . 
     In this way, in the fifth concrete example, particularly, it is possible to output from the set top box  1500  an adequately right processed analog signal with the copyright protection information superimposed thereon by the electronic watermark. Accordingly, this is preferred where an analog signal output is required. 
     Note that, in the configuration shown in  FIG. 14 , the copy control information requested by the content owner  1200  is converted to a control descriptor by the broadcaster  1300  and added to the content data. If the broadcaster  1300  is a sufficiently reliable institution, there is no problem in employing such a configuration. However, when the content owner  1200  sets control itself for a certain reason, in the same way as the case of the third concrete example, the control descriptor may also be set by the content owner  1200 . 
     Sixth Concrete Example 
     An explanation will be made of a sixth example of concrete application of the content distribution system  1100  by referring to  FIG. 15 . 
     In the sixth concrete example, the digital output from the set top box  1500  is made either of monitor connection use DVI (digital visual interface) and copyright protected output (DVI-CP) and enable the analog output to be turned ON/OFF. 
     In this case, the content owner  1200  superimposes the copy control information desired to be set on the content data in the form of an electronic watermark at the electronic watermark superimposing unit  1208 , encrypts the content data with that electronic watermark information superimposed thereon at the encryptor  1210  by using the encryption key Ka, and transfers the encrypted content data to the broadcaster  1300 . 
     The broadcaster  1300  adds the unique control descriptor to the encrypted content data transferred from the content owner  1200  at the control descriptor adder  1306 , then performs the encryption for the conditional access at the encryptor  1302  by using the encryption key Kb and transfers the same. 
     The set top box  1500  receiving this decrypts the encryption for the conditional access performed by the broadcaster  1300  at the decryptor  1502  by using the encryption key Kb, detects the control descriptor added by the broadcaster  1300  from this decrypted signal at the control descriptor detector  1512 , and outputs the same to the decision controller  1514 . 
     Also, the signal decrypted at the decryptor  1502  is further decrypted at the decryptor  1504  by using the encryption key Ka, and the copy control information superimposed in the form of the electronic watermark by the content owner  1200  is detected from this decrypted signal at the electronic watermark detector  1506  and output to the decision controller  1514 . 
     The decision controller  1514  performs the decision for controlling the usage of the received content data based on the copy control information set by the content owner  1200  input from the electronic watermark detector  1506  and the control descriptor set by the broadcaster  1300  input from the control descriptor detector  1512  and controls the output data based on the decision. 
     Concretely, the decision controller  1514  performs a decision as to whether to output the baseband data or output data encrypted by the DVI-CP as the digital output from the set top box  1500 , makes a decision as to whether or not to output an analog signal, and outputs control signals based on the results of the decision to the output switch  1510  and an analog output switch  1522 . 
     Further, the signal decrypted at the decryptor  1504  is encrypted to DVI-CP at an encryptor  1520  or directly applied to the output switch  1510 . Either is selected at the output switch  1510  and output as the digital output. 
     On the other hand, the signal decrypted at the decryptor  1504  is input to the analog signal encoder  1518 , converted to an analog signal here, applied to the analog output switch  1522 , selected at the analog output switch  1522  under the control of the decision controller  1514 , and output as the analog output. 
     In this way, in the sixth concrete example, a digital video signal can be output from the set top box  1500  by DVI as the RGB baseband signal or an encoded signal. Also, a suitably right processed analog signal with the copyright protection information superimposed thereon by the electronic watermark can be selectively output. 
     Modification 
     Note that the present invention is not limited to the above embodiments. Various preferred modifications are possible. 
     For example, the apparatus connected to the set top box  1500  and used in the content distribution system  1100  was a display device for displaying a video signal, but the invention is not limited to this. Any image processing device can be connected too. For example, it is also possible to connect a recording device for recording the output data or connect a transfer device for transferring the output data. 
     Further, the output I/F of the set top box  1500  is not limited to the IEEE1394 and DVI shown in the above embodiments. Any I/F can be used. 
     Further, the means for transmitting the data between the broadcaster  1300  and the set top box  1500  is not limited to a broadcasting means. Any information transmitting means can be applied. 
     Further, not limited to a so-called broadcast, a transferring means for transmitting the desired content data to a requesting set top box  1500  in response to a request from the set top box  1500  can be used too. 
     Further, in the present embodiment, the content to be distributed was a video signal and a video signal containing an audio signal, but it is not limited to this. It can be applied to the distribution of any content data. For example, it can be used as a distribution system of audio data, still image data, game software programs, any program software, etc. 
     As explained above, in the present invention illustrated in the first and second embodiments, information indicating a receiver not having a function enabling copying of content indicated by the content signal is held by utilizing the transferred content signal. When information indicating the connected receiver is included in this held information, the non-copyright protected content signal is transmitted. For this reason, a signal compatible with the receiver can be transmitted in accordance with whether or not the receiver has a function enabling copying of the content. 
     Further, when it is decided that the content is copyright protected, a copyright protected content signal is transferred. When it is decided that information indicating the connected receiver is included in the held information, a non-copyright protected content signal is transferred regardless of whether the content is copyright protected. For this reason, so far as the receiver does not have a function for enabling copying, even copyright protected content can be used. 
     Further, a change in connection of the connected receiver is monitored for while transferring a content signal of copyright protected content data without providing copyright protection. When a change in connection is detected, transmission of a non-copyright protected content signal is prohibited. For this reason, even if a receiver having a function for enabling copying is switched to while content signal is being transmitted without providing copyright protection, the content can be copyright protected. 
     Further, since the information indicating the receiver is held in a tamper-proof updateable manner, copyright protection can be correctly provided to the content. Further, even if a new receiver not having a function enabling copying is connected, it can be easily handled by updating the information. 
     Further, it is possible to provide a data distribution system and a data distribution method enabling a content owner to directly control copying as desired while using a standard apparatus as a processor after the receiver. 
     Further, it is possible to provide a data receiver used in such a content distribution system, receiving the distributed content data, performing adequate right processing, and outputting the content data in a usable manner. 
     Further, it is possible to provide a data provider and a data providing method for providing content data to be distributed in a state where the owner of the content can control the usage thereof. 
     Further, it is possible to provide a data transferer for transferring the data provided in this way. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to a music distribution system for distributing for example musical works via a network, hardware used for that music distribution system, and data processing methods in that music distribution system.