Patent Publication Number: US-8527424-B2

Title: Content management program, method and device

Description:
This application is a divisional of U.S. patent application Ser. No. 11/657,107, filed Jan. 24, 2007, now U.S. Pat. No. 8,095,469 which was a continuing application filed under 35 U.S.C. §111(a) of PCT International Application Number PCT/JP2004/012266 filed Aug. 26, 2004, the contents of both of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a content management program, method and device in a ubiquitous environment that manage a content given an access right of a user based on copyright, and in particular, it relates to a content management program, method and device in which the content is usable while being transferred among a plurality of devices. 
     BACKGROUND ART 
     At present, various types of contents such as music, images, and documents are digitalized, and because of such digitalization, the content can be easily copied, and above all, it is a problem of illegal copy that causes a serious concern. 
     If an illegal copy equivalent to infringement of the copyright goes into circulation, not only the distributor and the copyright holder suffers from a loss, but also the consumer is unfavorably affected. For this reason, the content of higher value is required to be made use of under the system environment of the digital copyright management mounted with a copy right management function. 
     Usually, in the digital copyright management system, the content is encrypted, and the encrypted content and its encryption key are distributed to an access right owner who is given a permit to access the encrypted content. The access right owner stores the encrypted content and the encryption key into one device, and when accessing, performs the decryption of the encrypted content by using the encryption key, and then, accesses the content. 
     Further, when an access is desired to be made to the content by another device, it is necessary to transfer the encrypted content and the encryption key to another device. However, in order to prevent the content from being copied, a mechanism is adapted to control in such a manner that at least a pair of encryption key and encrypted content is not stored in a plurality of devices at the same time.
     Patent Document 1: Japanese Patent Application Laid-Open No. 2000-134193   Patent Document 2: Japanese Patent Application Laid-Open No. 2000-285028   

     However, in such conventional digital copy right management system, when the access right owner tries to access the content acquired by a different device according to needs, it is necessary to transfer a pair of encryption key and encrypted content to the device in advance, and this hampers the usability of the user. 
     As a solution to cope with this problem, there is a method of using a server that performs key management, that is, a key management server. The access owner stores an encrypted content in a plurality of devices. At a point of time when the content is accessed, first, the owner accesses the key management server, and transfers the encryption key to the devices from the key management server or copies the encryption key with a time limit, and decodes the encrypted content by using this encryption key. 
     When the encryption key is transferred, the encryption key is returned to the key management server after the use is discontinued. When a copy is taken with a time limit, the encryption key becomes unusable after the set period of time elapses. 
     However, in the method of using the key management server, there is a problem that the key management server is absolutely necessary and that the communication with the key management server is absolutely necessary when the access is made to the content. 
     On the other hand, even in the field of Television Broadcasting, to prevent the problem of outflow into the internet of illegal copies readily made accompanied with the start of the digital broadcasting, the BS digital and terrestrial digital broadcasting programs in Japan have introduced the copy control signal CCI (Copy Control Information) to realize the [copy once] which permits video recording one time only from Apr. 1, 2004. 
     However, the content received and recorded in a hard disk drive and the like by HDTV (High Definition Television) resolution is put into a state of “copy once” by one time recording, and is applied with a copy protection. Consequently, when such content is once transferred to memory cards such as SD card by being transcoded into low resolution of QVGA (Quarter Video Graphic Array) of 320×240 pixels in order to watch by mobile terminal, the original HDTV content is eliminated when transferred. Hence, even when the QVGA content of the memory card is returned to the hard disk drive later, it cannot be restored to the original HDTV resolution, and the broadcast content of the HDTV resolution applied with protection of the copy once is lost, and cannot be reproduced again, thereby causing a problem. 
     An object of the present invention is to provide a content management program, method and device capable of taking a copy of one content and making it accessible for a plurality of devices, while maintaining constraint of a copy right use of copy once. 
     DISCLOSURE OF INVENTION 
     An object of the present invention is to provide a content management program, method and program capable of converting the content to the low resolution and transferring it to another device, and after that, when it is returned back, restoring it back to the original resolution, while maintaining a use restriction of copy once. 
     Means for Solving the Problem 
     (Content Copy and Encryption Key Transfer) 
     The present invention provides a content management program to be executed by a computer of the device connected to another device through a network. 
     The content management program of the present invention is characterized by allowing a computer to execute: 
     a content storing step of storing an encrypted content and the encryption key under a copy right use condition to prohibit a copy by the device having received the content; 
     a decoding step of decoding the encrypted content by the encryption key; 
     a content copy step of copy-transferring the encrypted content with another device through a network; and 
     an encryption key transfer step of transferring the encryption key with another device through the network. 
     Here, the encryption key transfer step deletes the encryption key stored after the encryption key of the content storage unit is copy-transferred to another device through the network. 
     The encryption key transfer step registers a device storing the encryption key for each content in an encryption key management table, and the decoding step, when decoding the encrypted content, obtains the encryption key by a transfer request for the device storing the encryption key recognized from the management table, and decodes the encrypted content. 
     The encryption key transfer step, when having transferred the encryption key to another device, renews its own encryption key management table, and at the same time, advises another device of the transfer information and allows the device to renew its encryption key management table. 
     The device connected through the network is a device stored by the same user registered in a device management table. 
     Further, the device connected through the network may include a device stored by another user registered in the device management table. The encrypted content is any one of the music, screen image, and document under a copy right or a combination thereof. 
     The present invention provides a content management method of the device connected to another device through the network. 
     The content management method of the present invention is characterized by comprising: 
     a content storing step of storing the encrypted content and the encryption key under a use copy right condition to inhibit a copy by a device having received the copy in a content storage unit; 
     a decoding step of decoding the encrypted content by the encryption key; 
     a content copy step of copying-transferring the encrypted content with another device through the network; and 
     an encryption key transfer step of transferring the encryption key with another device through the network. 
     The present invention provides a content management device connected to another device through the network. 
     The content management device of the present invention is characterized by comprising: 
     a content that stores the encrypted content and the encryption key under a copy right use condition to inhibit a copy by a device having received the copy; 
     a decoding unit that decodes the encrypted content by the encryption key; 
     a content copy unit that copies/transfers the encrypted content with another device through the network; and 
     an encryption key transfer unit that copy-transfers the encryption key with another device through the network. 
     (Content Management Program) 
     The present invention provides a content management program of the content which is broadcast and received. 
     The content management program of the present invention is characterized by allowing a computer to execute: 
     an access information setting step of setting access information that controls whether or not the reproduction of the content should be made for each content stored in the content storage unit; 
     a content reproducing step of reproducing the content when the accessing information is shown as reproducible, and prohibiting the reproduction of the content when the access information is shown as not reproducible; 
     a content transfer step of converting the resolution of the content stored in a content storage unit and transferring the content after the conversion to another device; and 
     an access information control step of setting the access information to be reproducible when the content is stored in the content storage unit, and prohibiting the reproduction by setting the access information to be not reproducible when the content after the conversion is transferred to another device, thereby prohibiting the reproduction, and moreover, setting the access information to be reproducible, thereby making it reproducible when the content transferred to another device and converted thereafter is not reproducible. 
     Here, the resolution is a dot density in the case of image (moving image and still image) data, and is a bit rate in the case of voice data. 
     Further, the content management program of the present invention is characterized by allowing the computer to execute a dummy content control step in which a dummy content number showing the number of contents stored in another device in a reproduction prohibiting state which sets the access information to be not reproducible is provided, and the transfer processing of the content to another device is prohibited when the value of the dummy content counter reaches a predetermined threshold value. 
     The content transfer step converts the content stored in the content storage unit into the content of a low resolution corresponding to the device of the transfer destination, and 
     transfers the content after the conversion. 
     The present invention provides a content management program to be executed by the computer of a copy recording apparatus. 
     This program allows a computer to execute: 
     an access information setting step of setting the access information that control the presence or absence of the reproduction of the content for each content stored in the content storage unit; 
     a content reproducing step of reproducing the content when the access information is shown as reproducible and prohibiting the reproduction of the content when the access information is shown as not reproducible; 
     a content transfer step of converting the resolution of the content stored in the content storage unit and transferring the content after the conversion to another device; and 
     an access information control step of setting the access information to be reproducible, thereby making it reproducible when the content is stored in the content storage unit, and setting the accessing information to be not reproducible, thereby prohibiting the reproduction when the content is transferred to another separate device. 
     In this case also, the content management program allows the computer to further execute a dummy content limiting step 
     of providing a dummy content number showing the number of contents stored in another device in a reproduction prohibiting state which sets the access information to be not reproducible and prohibiting the transfer processing to another device when the value of a dummy content counter reaches a predetermined threshold value. 
     The content transfer step converts the resolution of the content stored in the content storage unit into the content of a low resolution corresponding to the device of the transfer destination and transfers the same, and executes a transfer processing not including the content when the content stored in the content storage unit is returned to the device of the transfer source storing the content of a high resolution. 
     The content transfer step leaves the stored content alone as it is or deletes it when the content stored in the content storage unit is returned to the device of the transfer source storing the content of a high resolution. 
     The content transfer step transfers the content to another device through a network connection or a detachably attachable storage medium. Further, when the content after the conversion is not reproducible by another device, the content after conversion is returned. 
     Another mode of the present invention provides a content management program executed by a computer of the device storing and reproducing a broadcast signal. 
     The program of the present invention of this case is characterized by allowing the computer to execute: 
     a content storing step of storing in the content storage unit a plurality of same contents reproduced in parallel by 
     a plurality of CODEC step of receiving a signal and reproducing the same content in parallel and a plurality of CODEC steps; 
     a flag control step turning on any one of the access information set for each same content stored in the content storage unit and setting the corresponding content to be reproducible, and at the same time, prohibiting the reproduction of the corresponding content by turning off all the remaining access information; and 
     a content reproducing step of selecting the content with the access information turned on from among the plurality of same contents and reproducing the same. 
     In such content management program of the present invention, the content is a television broadcast signal received with a copy of one time only taken as a copy right use condition. 
     (Content Management Method) 
     The content management method of the present invention is characterized by comprising: 
     an access information setting step of setting access information that controls whether or not the reproduction of the content should be made for each content stored in the content storage unit; 
     a content reproducing step of reproducing the content when the accessing information is shown as reproducible, and prohibiting the reproduction of the content when the access information is shown as not reproducible; 
     a content transfer step of converting the resolution of the content stored in a content storage unit and transferring the content after conversion to another device; and 
     an access information control step of setting the access information to be reproducible when the content is stored in the content storage unit, and prohibiting the reproduction by setting the access information to be not reproducible when the content after conversion is transferred to another device, and moreover, setting the access information to be reproducible thereby making the reproduction possible when the content transferred to another device and converted thereafter becomes not reproducible. 
     Another mode of the content management method according to the present invention is characterized by comprising: 
     an access information setting step of setting access information that controls the presence or absence of reproduction of the content for each content stored in a content storage unit; 
     a content reproducing step of reproducing the content when the accessing information is shown as reproducible, and prohibiting the reproduction of the content when the access information is shown as not reproducible; 
     a content transfer step of converting resolution of the content stored in a content storage unit and transferring the content after conversion to another device; and 
     an access information control step of setting the access information to be reproducible, thereby making the reproduction possible when the content transferred from another device is stored in the content storage unit, and setting the access information to be not reproducible, thereby prohibiting the reproduction when the content is transferred to another device. 
     Another mode of the content management method according to the present invention is characterized by comprising: 
     a content storing step of storing a plurality of CODEC steps reproducing the same content in parallel by receiving signals and a plurality of same contents reproduced in parallel 
     by the plurality of CODEC steps in a content storage unit; 
     a flag control step of turning on any one of the access information set for each same content stored in the content storage unit and setting the corresponding content to be reproducible, and at the same time, turning off all the remaining access information and prohibiting the reproduction of the corresponding content; and 
     a content reproduction step of selecting the content with the access information turned on from among the plurality of same contents and reproducing the same. 
     (Content Management Device) 
     The present invention provides a content management device. The content management device of the present invention is characterized by comprising: 
     an access information setting unit that sets access information that controls whether or not a reproduction of the content should be made for each content stored in a content storage unit; 
     a content reproduction unit that reproduces the content when the accessing information is shown as reproducible, and prohibiting the reproduction of the content when the access information is shown as not reproducible; 
     a content transfer unit that converts a resolution of the content stored in the content storage unit and transferring the content after conversion to another device; and 
     an access information control step of setting the access information to be reproducible when the content is stored in the content storage unit, and setting the access information to be not reproducible, thereby prohibiting the reproduction when the content after conversion is transferred to another device, and moreover, setting the access information to be reproducible, thereby making the reproduction possible when the content transferred to another device and converted thereafter is not reproducible. 
     Another mode of the content management device of the present invention is characterized by comprising: 
     an access information setting unit setting access information that controls the presence or absence of reproduction of the content for each content stored in a content storage unit; 
     a content reproduction unit that reproduces the content when the accessing information is shown as reproducible, and prohibiting the reproduction of the content when the access information is shown as not reproducible; 
     a content transfer unit that converts a resolution of the content stored in the content storage unit and transferring the content after conversion to another device; and 
     an access information control step of setting the access information to be reproducible, thereby making the reproduction possible when the content transferred from another device is stored in the content storage unit, and setting the access information to be not reproducible, thereby prohibiting the reproduction when the content is transferred to another device. 
     Another mode of the content management device of the present invention is characterized by comprising: 
     a content that stores a plurality of CODEC steps reproducing the same content in parallel by receiving signals and a plurality of same contents reproduced in parallel by the plurality of CODEC steps in a content storage unit; 
     a flag control unit that turns on any one of the access information set for each same content stored in the content storage unit and sets the corresponding content to be reproducible, and at the same time, prohibits the reproduction of the corresponding content by turning off all the remaining access information; and 
     a content reproduction unit that selects the content with the access information turned on from among the plurality of same contents and reproduces the same. 
     Incidentally, the detail of the content management method and the device in the present invention is basically the same as the case of the content management program. 
     Effect of the Invention 
     (Content Copy and Key Transfer) 
     According to the present invention, the access right owner can use the encrypted content applied with the constraint condition of a copy once which permits a copy of just one time by the device only accessing the content by using the encryption key without requiring the key management server. 
     Further, the encrypted content is copied in a plurality of devices, and at the same time, all the devices recognize which device stores the encryption key, and therefore, even when the access owner changes the device to be used or changes the place in which the device is used, the encryption key stored in another device is automatically obtained, so that the user can access the encrypted content, and unless one content is simultaneously used by the plurality of devices, while maintaining the constraint condition of the copy one, the access can be made freely, and usability when using the content can be improved to a large extent. 
     (Content Management) 
     According to the content management of the present invention, for example, the content of a HDTV resolution received and recorded is left alone as it is, and is converted into a low resolution of another device, thereby the content is stored, while the contents different in resolution of the same broadcast are stored in a plurality of devices, but the access information is set to be reproducible just for one set only, thereby the use of the content is made possible, and all the other devices set the access information to be not reproducible, so that the use of the stored contents is prohibited. As a result, even when the contents are stored in the plurality of devices, a video storage state applied with a protection of the copy once that limits the content to be usable to one content only is substantially realized. 
     When the content converted into the low resolution is restored, the original high resolution content becomes usable. In this case, the transfer of the content from the low resolution to the high resolution is not performed, but by creating the same state as when the access information is transferred, the original high resolution content is put into reusability, and even when the high resolution broadcast content once received and recorded is changed to the low resolution, and is transferred to another device, the content thereof will never be lost. 
     Further, when the receiving and recording device is provided with a plurality of CODEC functions, the broadcast of the same HDTV resolution is received and recorded in parallel, and the condition of the copy once is satisfied individually, and therefore, if left alone as it is, the content equivalent to several minutes of the CODEC is recorded, and this means that more than two copies are made, and the condition of the copy once is broken. With respect to the receiving and recording by the multiplex CODEC also, only one key from among the access keys set respectively is turned on, and the content usable for one time is only one recorded content, and the recording condition of the copy once can be maintained even for the multiplex CODEC. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an explanatory drawing of device network environment adapted to the present invention; 
         FIG. 2  is a block diagram of a device comprising content management functions of the present invention; 
         FIG. 3  is an explanatory drawing of the device information database of  FIG. 2 ; 
         FIG. 4  is an explanatory drawing of the content database of  FIG. 2 ; 
         FIG. 5  is a block diagram of hardware environment of a computer adapted to the present invention; 
         FIGS. 6A and 6B  are time charts of the processing to access an encrypted content by using an encryption key under a use condition of copy once between the devices according to the present invention; 
         FIGS. 7A and 7B  are flowcharts of the host device processing of  FIG. 2 ; 
         FIGS. 8A and 8B  are flowcharts of the client device processing of  FIG. 2 ; 
         FIG. 9  is a block diagram of equipment environment adapted to a broadcast content according to the present invention; 
         FIGS. 10A and 10B  are block diagrams of a functional configuration of a high resolution device and a low resolution device of  FIG. 9 ; 
         FIGS. 11A to 11C  are explanatory drawings of a transfer processing accompanied with a resolution conversion of the broadcast content of  FIGS. 10A and 10B ; 
         FIGS. 12A and 12B  are time charts of the transfer processing of the broadcast content of  FIGS. 11A to 11C ; 
         FIGS. 13A and 13B  are flowcharts of a video transfer processing in the high resolution device of  FIGS. 10A and 10B ; 
         FIG. 14  is a flowchart of a video transfer processing in the low resolution device of  FIGS. 10A and 10B ; 
         FIG. 15  is a flowchart of the video transfer processing subsequent to  FIG. 14 ; 
         FIG. 16  is an explanatory drawing of the device environment that transfers the broadcast content by using a SD memory; 
         FIG. 17  is a block diagram of another device environment adapted to the broadcast content management processing of the present invention; 
         FIGS. 18A and 18B  are block diagrams of the device configuration of the high resolution device and a middle resolution device of  FIG. 17  managing the number of dummy contents; 
         FIGS. 19A and 19  B are explanatory drawings of the transfer processing accompanied with the resolution conversion of the broadcast content of  FIGS. 18A and 18B ; 
         FIGS. 20A and 20B  are explanatory drawings of a transfer processing subsequent to  FIGS. 19A and 19B ; 
         FIG. 21  is an explanatory drawing of the transfer processing subsequent to  FIGS. 20A and 20B ; 
         FIGS. 22A ,  22 B and  22 C are time charts of the transfer processing of the broadcast content of  FIG. 17 ; 
         FIGS. 23A and 23B  are flowcharts of the video transfer processing in the high resolution device of  FIGS. 18A and 18B ; 
         FIGS. 24A and 24B  are flowcharts of the video transfer processing in the middle resolution device of  FIGS. 18A and 18B ; 
         FIG. 25  is a flowchart of the video transfer processing subsequent to  FIGS. 24A and 24B ; 
         FIG. 26  is a flowchart of a dummy content count processing in  FIGS. 18A and 18B ; 
         FIGS. 27A and 27B  are explanatory drawings of the transfer processing accompanied with the resolution conversion of the broadcast content in  FIGS. 18A and 18B  which leaves alone the content of the low resolution side at the time of returning to the high resolution side; 
         FIGS. 28A and 28B  are explanatory drawings of the transfer processing subsequent to  FIGS. 27A and 27B ; 
         FIG. 29  is an explanatory drawing of the transfer processing subsequent to  FIGS. 28A and 28B ; 
         FIG. 30  is a flowchart of the dummy content count processing in  FIGS. 27 to 29 ; 
         FIG. 31  is a block diagram of the functional configuration of the device performing recording by a multiplex CODEC according to the present invention; and 
         FIG. 32  is a flowchart of the multiplex CODEC processing of  FIG. 31 . 
     
    
    
     BEST MODE FOR CARRY OUT THE INVENTION 
     (Content Copy and Key Transfer) 
       FIG. 1  is an explanatory drawing of network environment adapted to the content management processing according to the present invention. In  FIG. 1 , as a device adapted to the content management processing of the present invention, a personal computer  10 , a portable music player  12 , and a car music player  14  owned by a certain user are cited as an example, and these devices are capable of communicating with one another through an internet  16 , and moreover, a music content can be purchased and downloaded from a music sales site  18 . 
       FIG. 2  is a block diagram of a device comprising content management functions. In  FIG. 2 , in this example, client devices  22  and  24  are connected to a host device  20  through a network  26 . The host device  20 , for example, is the personal computer  10  of  FIG. 1 , and is a device that obtains an encrypted content and an encryption key by purchasing the music from the music sales site  18 , for example, through the internet  16  by the user. 
     In contrast to this, the client devices  22  and  24 , for example, are the portable music player  12  and the car music player  14  of  FIG. 1 , and are devices that obtain and use copies of such as the encrypted content and music from the personal computer  10  as the host device  20 . 
     Incidentally, names of the host device and the client devices are relative, and the device that takes possession of the content first is simply referred to as a host device, and is not limited to such name. 
     The host device  20  is provided with a communication control unit  30 , a content processing unit  32 , a security storage unit  34 , a device information management table  36 , and an encryption key management table  38 . The content processing unit  32  is an application realized by executing a content processing program, and comprises a content management unit  40 , a content decoding processing unit  42 , a content copy processing unit  44 , and an encryption key transfer unit  46 . 
     The content management unit  40  through the internet  16 , as shown in  FIG. 1 , purchases a music of copy-once, for example, from the music sales site  18 , thereby obtaining an encrypted content and an encryption key of the music, and stores it in a security storage unit  34  as an encrypted content  48  and an encryption key  50 . 
     The content decoding processing unit  42 , under the condition that the encryption key  50  is stored in the security storage unit  34 , decodes the encrypted content  48  by the encryption key  50 , and performs utilization of an output display and the like. 
     The content copy processing unit  44  copies/transfers the encrypted content  48  stored in the security storage unit  34  between the client devices  22  and  24  through the network  26  and stores the same. The encryption key transfer unit  46  transfers the encryption key  50  stored in the security storage unit  34  between the client devices  22  and  24  through the network  26 . 
     Here, the copy processing of the encrypted content  48  by the content copy processing unit  44  is performed such that the encrypted content  48  is read from the security storage unit  34  and is transferred to the client devices  22  and  24 , and after that, the encrypted content  48  is left alone. 
     In contrast to this, in the encryption key transfer unit  46 , the encryption key  50  is read from the security storage unit  34 , and for example, is copied/transferred to the client device  22 , and after that, the encryption key  50  in the security storage unit  34  is deleted. By such processing of the encryption key transfer unit  46 , the encryption key  50  is put into a state of being stored in either one only of the host device  20 , the client devices  22  and  24 , and by this state, an access to the content is made possible under a copy right use condition of copy-once that permits a copy of one time only. 
       FIG. 3  is an explanatory drawing of a device information management table  36  provided in the host device  20  of  FIG. 2 . In the device information management table  36 , device names adapted to the content management processing of the present invention and positions on the network are registered. 
     In the example of  FIG. 2 , as device names, a device  20 , a device  22  and a device  24  are registered, and as positions on the network, an address a, an address b, and an address c are registered. 
     The device adapted to the content management processing of the present invention, which is registered in this device information management table  36 , is a device owned basically by the same user. However, if permitted by the user, a device owned by another party is registered in the device information management table  36 , and can be included in the target devices of the content managing processing of the present invention. In this manner, when the device of another party is registered in the device information management table  36 , it is possible to make use in such a manner that the content obtained by a certain user is lent out to a third party under the constrain condition of copy-once and the content is allowed to be used. 
       FIG. 4  is an explanatory drawing of an encryption key management table  38  provided in the host device  20  of  FIG. 2 . The encryption key management table  38  is table information that registers in which position of the plurality of devices adapted to the content management processing of the present invention the encryption key exists. The encryption key management table  38  registers the content names, names of the storage devices of the key, and encryption systems. 
     Here, in the content name, a content A, a content B, and a content C are registered, and as the name of the storage device, a device  20 , a device  22 , and a device  24  are registered, and moreover, as the encryption system, a system α and a system β are registered. As the system α and system β as the encryption system, specifically, publicly known appropriate encryption systems are adapted, which are currently used for the contents of the copy right target. 
     Referring to  FIG. 2  again, the client devices  22  and  24  basically comprise the same functional configuration as the host device  20 , but the disadvantages of the client devices  22  and  24  are that they do not obtain new contents by themselves through the network, but take possession of the contents by the copy processing from the host device  20 . Of course, when the client devices  22  and  24  directly obtain the content through the internet, they are allowed to have the functions as the host device  20  with respect to that content. 
     The segment of the communication control unit  30 , the content processing unit  32 , the security storage unit  34 , the device information management table  36 , and the encryption key management table  38  in the host device  20  performs the transfer and decode processing of the encrypted content and the encryption key, and therefore, is configured by a tamper resistant module or software in order to protect the segment from un illegal access by the third party. 
     Further, the transfer of the encrypted content and the encryption key between the host device  20  and the client devices  22  and  24  is encrypted and exchanged by using a DTPC (Digital Transmission Content Protection) when the client devices  22  and  24  are connected to the personal compute configuring the host device  20  through, for example, an IEEE1394 port, and moreover, 
     when a LAN is used through the network  26 , the transfer is encrypted by using a SSL (Secure Socket Layer) or an IPSEC (IP security protocol). 
     Further, at the time of data transfer between the host device  20  and the client devices  22  and  24 , first, two-way authentication and key exchange are performed between two devices, and after that, they are encrypted, for example, by hybrid system, and then, the encrypted content and the data of the encryption key are transferred. 
     The encryption by the hybrid system is such that a pseudo random number is generated at a transmission side so as to fabricate a session key, and on the other hand, messages to be transmitted are encrypted by the session key so as to be combined, and after that, they are transmitted. At the reception side, based an encrypted secret key (private key), the received encryption key is decoded, and by the decoded session key, the received encrypted message is decoded. 
     The host device  20  in  FIG. 2  is realized, for example, by hardware resources of the computer as shown in  FIG. 5 . 
     In the computer of  FIG. 5 , a bus  201  of a CPU  200  is connected with a RAM  202 , a hard disk controller (soft)  204 , a floppy disk driver (soft)  210 , a CD-ROM driver (soft)  214 , a mouse controller  218 , a keyboard controller  222 , a display controller  226 , and a communication board  230 . 
     The hard disk controller  204  connects a hard disk drive  206 , and is loaded with a program to execute the content management processing of the present invention, and calls out a necessary program from the hard disk drive  206  at the computer activating time so as to be developed on the RAM  202  and executed by the CPU  200 . 
     The floppy disk driver  210  is connected with a floppy disk drive (hard)  212 , so that read/write can be made on a floppy disk (R). The CD-ROM driver  214  is connected with a CD drive (hard)  216 , so that data and program stored in CD can be read. 
     The mouse controller  218  transmits an input operation of the mouse  220  to the CPU  200 . The keyboard controller  222  transmits an input operation of the keyboard  224  to the CPU  200 . 
     The display controller  226  performs a display for a display unit  228 . The communication board  230  uses a communication line  232  including radio transmission, and performs communications with the devices within the network and the devices on the out of network through LAN. 
       FIGS. 6A and 6B  are time charts of the processing to access the encrypted content by using the encryption key under a use condition of one copy between the devices of the present invention. In  FIGS. 6A and 6B , first at step S 1 , the host device  20  purchases and inputs the encrypted content and the encryption key, for example, from a music distribution site through the internet and stores them. 
     Subsequently, at step S 2 , the host device  20  prepares a content menu and an encryption key management table, and distributes this table to another device. Then, at step S 101 , the client device  22  stores the content menu and the encryption key management table received from the host device  20 . Subsequently, at step S 102 , when the content from the menu is selected in the client device  22 , at step S 103 , the presence or absence of the storage of the encrypted content is checked. 
     If the encrypted content is not stored, the procedure proceeds to step S 104 , and a copy of the encrypted content is requested from the host device  20 . Upon receipt of this request, at step S 3 , the host device  20  copies/transfers the stored encrypted content to the client device  22  of a request origin. 
     At step S 105 , the client device  22  stores the transferred encrypted content. Of course, if the encrypted content selected by the menu at step S 103  is stored, the procedure skips steps S 104  and S 105 . 
     Next, at step S 106 , the presence or absence of the storage of the encryption key is checked. If the encryption key is not stored, by referring to the encryption key management table, it is confirmed that the key is currently stored in the host device  20 , and at step S 107 , a request for the transfer of the encryption key is made to the host device  20 . 
     Upon receipt of this request, the host device  20  reads the encryption key at step S 4 , and transfers it to the client device  22  of the request origin. After transferring the encryption key, at step S 5 , the host device  20  deletes the stored encryption key, and renews the encryption key management table. 
     Upon receipt of the transfer of the encryption key from the host device  20 , the client device  22  stores the encryption key at step S 108 , and after that, renews its encryption key management table. At the renewing time of this encryption key management table, a renewal result of the encryption key management table is informed to another device from either the transfer source or the transfer destination of the encryption key, thereby allowing its encryption key management table to be renewed. Subsequently, at step S 109 , the encrypted content is decoded and outputted by the encryption key obtained and stored by the transfer. 
       FIGS. 7A and 7B  are flowcharts of a host device processing in the host device  20  of  FIG. 2 . In  FIGS. 7A and 7B , at step S 1 , the encrypted content and the encryption key are inputted and stored, and at step S 2 , the generation of the content menu and the registration of the storing position for the encryption key management table are performed. 
     Next, at step S 3 , the presence or absence of the request for the copy of the encrypted content is checked, and upon receipt of the request for the copy, the procedure proceeds to step S 4 , and copies/transfers the encrypted content to the requesting device. 
     Subsequently, at step S 5 , the presence or absence of a use request for the content in the host device itself is determined, and if the use request does not exist, the procedure proceeds to step S 7 , and by referring to the encryption management table, a request for the transfer of the encryption key is made to the device currently storing the encryption key, and at step S 8 , the obtained encryption key is stored, and the encryption key management table is renewed. 
     At step S 9 , the encrypted content is decoded by the encryption key, and is outputted. At step S 6 , if the encryption key exists, the procedure skips steps S 7  to S 8 , and proceeds to step S 9 . 
     Next, at step S 10 , the presence or absence of the transfer request for the encryption key from another device is checked, and if the transfer request exists, at step S 11 , the stored encryption key is read and transferred, and the stored encryption key is deleted. Subsequently, at step S 12 , the storing position of the encryption key management table is renewed. The processing of these steps S 3  to S 12  are repeated at step S 13  until the stop instruction of the host device is received. 
       FIGS. 8A and 8B  are flowcharts showing the processing in the client devices  22  and  24  of  FIG. 2 . In  FIGS. 8A and 8B , at step S 1 , the content menu is displayed, and at step S 2 , by looking through the menu display, whether or not the content selection was made is checked. 
     If the content selection was made, the procedure proceeds to step S 3 , and whether or not the encrypted content is stored is checked. If not stored, at step S 4 , a request for the transfer of the copy of the encrypted content is made to the host device, and the copy is stored. 
     Subsequently at step S 5 , whether or not the encryption key is stored is checked, and if not stored, at step S 6 , a request for the transfer of the encryption key is made to the storage device identified by referring to the encryption key management table. At step S 7 , when the encryption key is obtained from a transfer request destination, the obtained encryption key is stored, and the encryption key management table is renewed. 
     At step S 8 , the encrypted content is decoded by the encryption key, and is outputted. At step S 5 , when the encryption key is stored, the processing at steps S 6  and S 7  are skipped. 
     Subsequently, at step S 9 , the presence or absence of the transfer request of the encryption key from another device is checked, and if the transfer request exists, at step S 10 , the encryption key is transferred to the requesting device, and the stored encryption key is deleted, and at step S 11 , the encryption key management table is renewed. 
     The processing of these steps S 1  to S 11  are repeated at step S 12  until the stop instruction for the client device is received. 
     Incidentally, in the content management processing of the present invention, it is necessary that all the devices registered in the device information table are always in a connected state. However, in an actual using state, there are often the cases where a specific device is not always connected due to shut down of a power source, and if the encryption key is stored in the device not always connected, the encryption key cannot be transferred to another device always connected with a result that the encrypted content cannot be used by being decoded. 
     Hence, it is desirable to provide such processing functions that the device with the power source turned off after use is provided with the functions of an auto power up control in which the power source can be automatically inputted by the control from another device, and in a connected state of the devices with the power source separated, the power source is automatically turned on upon receipt of the transfer request of the encryption key, and the encryption key is read for the transfer request, and is transferred, and the power source is turned off by the completion of the transfer. 
     Further, the segment necessary only for the transfer of the encryption key and the encrypted content enabling the device to be always connected is required to be operated by full-time power supply, and the segment other than this may be turned on and off by power switch and the like. 
     Further, the device as the target of the present invention can be adapted to a user terminal such as PDA, and mobile phone, in addition to the personal computer and car terminal. 
     Further, as the content to be accessed by the use condition of copy-once, all sorts of digital contents such as a music content, screen image content, karaoke content, map content, game content, and electronic book, can be made the target 
     (Broadcast Content) 
       FIG. 9  is a block diagram of device environment adapted to a broadcast content management processing according to the present invention. Incidentally, in this embodiment, though a resolution shown by a dot density is handled with image data taken as an example, the content taken as the target of the present invention also includes music data, and the resolution in the case of the music data is shown by a bit rate. 
     In  FIG. 9 , this embodiment connects a high resolution device  100  with a low resolution device through a network  106 . 
     The high resolution device  100 , for example, is a HDTV recording device incorporating a hard disk drive, and comprises a HDTV tuner  110  and a content storage unit  112  using the hard disk drive, and the content storage unit  112  stores a HDTV content  114  which is a HDTV television broadcast program received and reproduced by the HDTV tuner  110 . 
     The low resolution device  104 , for example, is a QVGA mobile terminal incorporating a flush memory  120 , and stores a content which transcodes HDTV content  114  stored in the high resolution device  100  into low resolution QVGA content  122 . 
     Such high resolution device  100  and the low resolution device  104  adapted to the present invention are the devices abiding by a rule of copy control based on copy control information (CCI) for once copy that permits recording of one time only in the receive recording of the HDTV broadcast, and moreover, comprise a certificate issued by certification organizations in order to perform communications for protection of the digital copy right between the devices. 
     This certificate includes public key information on each device. 
     As the encrypted communications performed between the high resolution device  100  and the low resolution device  104 , for example, a hybrid system is adopted. The hybrid system exchanges public keys after two-way authentication between the devices is performed, and a transmission source sends a transmission message by encrypting it by a session key generated by a pseudo random processing, and this session key is encrypted by the public key received from the other party, and is sent. 
     At the receiving side, the session key is decoded from the encrypted session key based on the secret key, and by the decoded session key, the encrypted message is decoded, thereby taking out the message. 
       FIGS. 10A and 10B  are block diagrams of the functional configurations of the high resolution device and the low resolution device of  FIG. 9 . In  FIGS. 10A and 10B , the high resolution device  100  is provided with a communication control unit  124  and a content management unit  126  in addition to the HDTV tuner  110  and the broadcast content storage unit  112 . 
     The content management unit  126  is an application realized by the execution of the content management program. The content management unit  126  is provided with an access flag (access information setting unit) setting unit  128 , an access flat control unit (access information control unit)  134 , a content reproduction unit  136 , and a content transfer unit  138 . 
     The low resolution device  104  connected to the high resolution device  100  through the network  106  comprises a communication control unit  242 , a content management unit  244 , and a broadcast content storage unit  246 . The content management unit  244  is a function realized by the execution of the content management program. 
     The content management unit  244  is provided with an access flag setting unit  248 , an access flag control unit  254 , a content transfer unit  228 , and a content reproduction unit  256 . 
     The access flag setting unit  128  functioning as the access information setting unit provided in the content management unit  126  of the high resolution device  100  sets an access flag  130  for controlling the presence or absence of the reproduction of the broadcast content when the high definition television broadcast signal taking a copy-once received by the HDTV tuner  110  as a use condition of the copyright is stored in the broadcast content storage unit  112  as a HDTV content  114 . The access flag  130  is set to 1 (on) when the HDTV content  114  is initially stored. The control of the setting of this access flag  130  is performed by the access flag control unit  134 . 
     The content reproduction unit  136  refers to the access flag  130  when the HDTV content  114  stored in the broadcast content  112  is reproduced, and performs the reproduction processing when the access flat  130  is set to 1 (reproducible), and prohibits the reproduction of the content when the access flag is set to 0 (not reproducible). 
     The content transfer unit  138  transcodes an original HDTV content  114  stored in the broadcast content storage  112  into the QVGA content in the low resolution device by a resolution conversion unit  140  and transmits it. 
     When the content is transferred by transcoding by the content transfer unit  138 , the access flag control unit  134  resets the access flag  130  of the HDTV content  114 , that has become the transfer source, to 0. Further, when the content transferred to the low resolution device  104  is returned, the access flag control unit  134  sets the access flag  130  to  1 , and makes the HDTV content  114  reproducible. 
     The functions of the access flag setting unit  248 , the access flag control unit  254 , the content reproduction unit  256 , and the content transfer unit  258  provided in the content management unit  244  at the low resolution device  104  side are also basically the same as the content management unit  126  of the high resolution device  100 . 
     Meantime, a point of difference lies in that, upon receipt of the transfer of the low resolution QVGA content  122  transcoded from the high resolution device  100 , it is stored in the broadcast content storage unit  246 , and accompanied with this, the access flag setting unit  248  sets the access flag  164 , and when it is stored, the access flag control unit  254  sets the access flag  164  to  1 , thereby making the reproduction by the content reproduction unit  256  possible. 
     Further, when the broadcast content is transferred to the low resolution device lower than the QVGA content  122 , the content transfer unit  258  performs transcoding by the resolution conversion unit  260  and transfers the broadcast content, and accompanied with this transfer, the access flag control unit  254  sets the access flag  164  to 0. Incidentally, 
     if there does not exist a device of resolution lower than the QVGA content, there is no need for the function of the content transfer unit  258 . 
       FIGS. 11A to 11C  are explanatory drawings of the transfer processing accompanied with the resolution conversion of the broadcast content in  FIGS. 10A and 10B .  FIG. 11A  shows a state in which the broadcast content in the high resolution device  100  is received and recorded, in which the received HDTV content  114  is stored, and at the same time, its access flag  130  is set to 1. 
     Next, as shown in  FIG. 11B , when the content is transferred from the high resolution device  100  to the low resolution device  104 , the HDTV content  114  in the high resolution device  100 , for example, is transcoded and transferred to the QVGA content  122  so as to be stored in the low resolution device  104 , and at this time, the access flag  130  of the high resolution device  100  which becomes a transfer source is set to 0, and the access flag  164  of the low resolution device  104  which becomes a transfer destination is set to 1. 
     In this state, there exist contents of the same broadcast content which are different in resolution in the high resolution device  100  and the low resolution device  104 , respectively. However, the content that can be reproduced is that of the low resolution device  104  only, whose access flag  164  is set to 1, and in the case of the high resolution device  100 , the content cannot be reproduced since the access flag  130  is set to 0, thereby the copy control rule of a copy-once required for the recording of the HDTV content can be maintained. 
       FIG. 11C  is an explanatory drawing in the case where the content is returned to the high resolution device  100  from the low resolution device  104 . When the QVGA content  122  of the low resolution device  104  is returned to the high resolution device  100 , the transfer processing is performed in which the transcoding of the content to the high resolution is not performed, that is, the transfer instruction only is sent to the high resolution device  100  without accompanied with the transfer of the content. 
     By this transfer to the high resolution side, the access flag  164  in the low resolution device  104  is set to 0, and the access flag  130  of the high resolution device  100  is set to 1, so that the content can be reproduced only in the high resolution device  100  that has become a transfer destination. 
     Incidentally, in the low resolution device  104  having become a transfer source, the QVGA content  122  stored after the transfer may be left alone or deleted. When the QVGA content  122  is left alone as illustrated, the access flag  164  is reset to 0. Further, when the QVGA content  122  is deleted after the transfer, the access flag  164  also may be deleted. 
       FIGS. 12A and 12B  is a time chart of the transfer of the broadcast content of  FIGS. 11A to 11C . In  FIGS. 12A and 12B , in the high resolution device  100 , at step S 1 , recording and storage are performed based on the receipt of the HDTV content, and when recording and storage are completed, at step S 2 , the access flag is set to 1. 
     Subsequently, at step S 3 , when the transfer request to the low resolution device  104  is discriminated, the procedure proceeds to step  4 , and the QVGA content of the low resolution is applied with transcoding, and after that, at step S 5 , the two-way authentication and the key exchange are performed with the low resolution device  104 . 
     This two-way authentication and the key exchange are performed based on a certificate issued by certification organizations which are, for example, set up in advance in the high resolution device  100  and the low resolution device  104 . 
     When the two-way authentication is successful and the key exchange is over, at step S 6 , the high resolution device  100   
     encrypts the QVGA content already applied with transcoding, and transmits it to the low resolution device  104 . 
     Since this encryption, for example, adopts a hybrid system, the QVGA content is encrypted by a session key generated as a pseudo random number, and moreover, the session key is encrypted by the public key notified from the low resolution device  104 , and both of them are combined and transmitted. 
     The low resolution device  104  receives/decodes and stores the encrypted QVGA content at step S 102 . This reception/decoding of the encrypted QVGA content is performed such that the encrypted session key is decoded based on its own secret key (private key), and the encrypted QVGA content is decoded by the decoded session key and is stored. 
     In the high resolution device  100  that has become the transmission source, at step S 6 , when the encryption transmission is completed, the access flag is reset to 0 at step S 7 , and the reproduction of the content in the high resolution device  100  is prohibited. On the other hand, in the low resolution device  104  that has become the transfer destination, at step S 102 , the encrypted QVGA content is received/decoded, and is stored, and after that, at step S 103 , the access flag is set to 1. Then, at step S 104 , the QVGA content can be reproduced under a condition that the access flag is set to 1. 
     Subsequently, at step S 105 , when the transfer request to the high resolution device  100  is discriminated, at step S 106 , the two-way authentication and the key exchange are performed, and after that, at step S 107 , the transfer instruction only is encrypted, and is transmitted. Then, at step S 108 , since the QVGA content is left alone, the access flag is set to 0. 
     In the high resolution device  100 , at step S 8 , the two-way authentication and the key exchange are performed with the low resolution device  104 , and after that, at step S 9 , the encrypted transfer instruction is decoded and recognized, and at step S 10 , the access flag is set to 1, thereby making the reproduction of the HDTV content possible. 
       FIGS. 13A and 13B  are flowcharts of the video transfer processing in the high resolution device of  FIGS. 10A and 10B . In  FIGS. 13A and 13B , at step S 1 , when the selection of the video broadcast program is performed, at step S 2 , a high definition television broadcast signal is received and reproduced, and is recorded and stored as the HDTV content. Then, at step S 3 , the access flag is set to 1. 
     Subsequently, at step S 4 , when the reproduction request is discriminated, at step S 5 , if the access flag is set to 1, the procedure proceeds to step S 6 , and the stored HDTV content is read, and is reproduced and outputted. If the access flag is set to 0, at step S 16 , an error message is outputted, and no reproduction output is performed. 
     Subsequently, at step S 7 , when the transfer request is discriminated, at step S 8 , the two-way authentication and the key exchange are performed with the device of the transfer destination, and after that, at step S 9 , the HDTV content is transcoded into the low resolution, for example, the SDTV (standard television) or the QVGA. Then, at step S 10 , the transcoded low resolution content is encrypted and transferred, and after that, at step S 11 , the access flag is set to 0. At step S 7 , if the transfer request does not exist, the procedure skips the steps S 8  to S 11 . 
     Subsequently, at step S 12 , when the transfer request from the low resolution side is discriminated, the procedure proceeds to step S 13 , and after performing the two-way authentication and the key exchange with the transfer source, performs the transfer processing without accompanied with the content. Then, at step S 14 , the access flag is set to 1, thereby making the reproduction of the HDTV content possible. These processing of steps S 1  to  14  are repeated until the stop instruction is received at step S 15 . 
       FIGS. 14 and 15  are flowcharts of the video transfer processing in the low resolution device of  FIGS. 10A and 10B . In FIG. 
       14 , at step S 1 , when the transfer request from the high resolution side is discriminated, at step S 2 , the encrypted content, for example, the SDTV content is received and decoded, and is stored, and at step S 3 , the access flag is set to 1. 
     At step S 4 , when the reproduction request is discriminated, at step S 6 , the SDTV content is read, and is reproduced and outputted under a condition that the access flag is set to 1 at step S 5 . When the access flag is set to 0, the procedure proceeds to step S 19 , and performs an error message output, and does not perform the reproduction. 
     At step S 7 , when the transfer request to the low resolution side is discriminated, at step S 8 , the two-way authentication and the key exchange with the device of the transfer destination are performed, and after that, at step S 9 , the stored content (SDTV) is converted into the low resolution QVGA of the transfer destination, and at step S 10 , the converted content is encrypted and transferred, and at S 11 , the access flag is reset to 0. 
     Subsequently at step  12  of  FIG. 15 , when the transfer request of the content from the low resolution side is made, the procedure proceeds to step S 13 , and the two-way authentication and the key exchange are performed with the transfer destination device, and the transfer processing without accompanied with the content is performed, and after that, at step S 14 , the access flag is set to 1. 
     Incidentally, the processing of steps S 7  to S 14  are not performed when the stored broadcast content is at the lowest resolution because no transcoding lower than the lowest resolution is possible. 
     Next, at step  15  of  FIG. 15 , when the transfer request toward the high resolution side is discriminated, at step S 16 , 
     the two-way authentication and the key exchange with the transfer destination device are performed, and the transfer processing with no content accompanied is performed, and at step S 17 , the access flag is reset to 0. The processing of these steps S 1  to S 17  are repeated at step S 18  until the stop instruction is received. 
       FIG. 16  is an explanatory drawing of another embodiment of the device environment that transfers the broadcast content of the present invention, and in this embodiment, the broadcast content is transferred between the devices by using a SD memory. 
     In  FIG. 16 , the high resolution device  100 , similarly to the case of  FIG. 9 , comprises the HDTV tuner  110  and the broadcast content  112 , and stores the HDTV content  114  received by the HDTV tuner  110 . 
     On the other hand, the low resolution device  104  is a device capable of connecting to the card slot of the SD memory  170 , and transcodes the HDTV content  114  stored in the high resolution device  110  into the QVGA content  122  so as to be stored in the SD memory  170 , and after that, inserts this SD memory  170  into the card slot of the low resolution device  104 , so that the content can be transferred and stored. 
     The functional configuration of the high resolution device  100  in the embodiment of  FIG. 16  is the same as that of  FIGS. 10A and 10B  except that an adaptor is provided for the SD memory  170 . Further, the low resolution device  104  is also the same as that of  FIGS. 10A and 10B  in functional configuration, and is different only in that an adaptor for the SD memory is provided. 
       FIG. 17  is a block diagram of another device environment adapted to the broadcast content management processing of the present invention, and in this embodiment, an example is cited of the case where the broadcast content is transferred among three devices such as the high resolution device  100 , the middle resolution device  102 , and the low resolution device  104 . 
     In  FIG. 17 , the high resolution device  100  and the low resolution device  104  are the same as that of  FIGS. 8A and 8B . Further, between both of them, there is provided a middle resolution device  102 , and as the middle resolution device  102 , for example, there is provided a device such as a DVD recorder, and as a middle resolution content that is transferred from the high resolution device  100  into a DVD medium  116  by transcoding, there is stored the SDTV content  118 . 
     The SDTV content is a standard television broadcast content, and corresponds to resolutions of a NTSE television broadcast signal and a PAL television broadcast signal. 
     In this example, the high resolution device  100  is connected to the middle resolution device  102  through the network  106 , and the middle resolution device  102  is connected to the low resolution device  104  through the network  108 . 
     Further, in the embodiment of  FIG. 17 , in addition to the access flag that makes the reproduction of the broadcast content possible, the number of dummy contents that limits the maximum number of the number of copies of the broadcast content is set and controlled. 
       FIGS. 18A and 18B  is a block diagram of the functional configuration of the high resolution device  100  and the middle resolution device  102  in  FIG. 17  that manages the dummy content to limit the number of copies of the broadcast content. In  FIGS. 18A and 18B , the high resolution device  100  comprises a communication control unit  124 , the content management unit  126 , the HDTV tuner  110 , and the broadcast content storage unit  112 . 
     The content management unit  126  is provided with the access flag setting unit  128 , the access flag control unit  134 , the content reproduction unit  136 , and the content transfer unit  138 , and is basically the same as the embodiment of  FIGS. 10A and 10B . 
     In addition, in the embodiment of the  FIGS. 18A and 18B , the access flag setting unit  128  is provided with the dummy content counter  132 . 
     The control of the dummy content counter  132  is realized by the counting of the number of dummy contents. In  FIG. 17 , when the original HDTV content  114  is transcoded, and is stored in the middle resolution device  102  as the SDTV content  118 , and moreover, the SDTV content  118  of the middle resolution device  102  is transcoded, and is stored in the low resolution device  104  as the QVGA content  122 , from among threes three devices, by any one of the devices, the access flag is set to 1, thereby making the reproduction possible, and in the remaining two devices, the access flags are set to 1, thereby prohibiting the reproduction, and the number of contents prohibited for reproduction is shown by the dummy content counter  132 . 
     The middle resolution device  102  of  FIGS. 18A and 18B  comprises a communication control unit  142 , a content management unit  144 , and a broadcast content  146 . The content management unit  144  is provided with a content transfer unit  158  comprising an access flag setting unit  148 , an access flag control unit  154 , a content reproduction unit  156 , and a resolution conversion unit  160 . 
     Although the configuration of this middle resolution device  102  is basically the same as the case of the low resolution device  104  as shown in  FIGS. 10A and 10B , a dummy content counter  152  is newly provided in the access flag setting unit  148 . Further, as a resolution conversion unit  160  of the content transfer unit  158 , for example, as shown in  FIGS. 18A and 18B , since the SDTV content  118  is stored in the broadcast content storage unit  146 , when the content is transferred to the low resolution device  104 , the SDTV content  118  is transcoded into the QVGA content  122 . 
       FIGS. 19A ,  19 B,  20 A,  20 B and  21  are explanatory drawings of the transfer processing accompanied with the resolution conversion of the broadcast content in  FIG. 17 .  FIG. 19A  shows a state in which the HDTV content  114  is received and recorded in the high resolution device  100 , and at this time, the access flag  130  is set to 1, and the dummy content counter  132  shows 0. 
     The dummy content counter  132  shows the number of contents stored in the device other than the device whose access flag is set to 1, and in this case, neither the middle resolution device  102  nor the low resolution device  104  stores the transcoded broadcast content, and therefore, the dummy content number counter  132  shows 0. 
     Next, as shown in  FIG. 19B , the content is transferred from the high resolution device  100  to the middle resolution device  102 . This transfer stores the HDTV content  114  by transcoding and transferring it into the SDTV content  118 , and the access flag  130  of the transfer source is reset to 0, and the access flag  150  of the transfer destination is set to 1. Further, the dummy content counter  152  is counted up by 1, and is set to 1. 
     Thus, the number of dummy contents relative to the transfer of the contents from the high resolution side is determined by the following formula.
 
(The number of dummy contents)=(The number of dummy contents of the transfer source)+1=0+1=1
 
     Next, as shown in  FIG. 20C , the content is transferred from the middle resolution device  102  to the low resolution device  104 . This transfer of the content stores the SDTV content  118  of the middle resolution device  102  in the low resolution device  104  by transcending and transferring it into the QVGA content  122 . By transfer of this content, the access flag  150  of the transfer source is reset to 0, and the access flag  164  of the transfer destination is set to 1. Further, the number of dummy contents in the low resolution device  104  of the transfer destination becomes as follows.
 
(The number of dummy contents)=(The number of dummy contents of the transfer source)+1=1+1=2
 
     Next, as shown in  FIG. 20B , a transfer that returns the content from the low resolution device  104  to the middle resolution device  102  will be described. Since the transcoding to the SDTV content  118  which becomes the high resolution of the QVGA content  122  of the low resolution device  104  is impossible, the transfer of the content is not performed, but the transfer processing of encrypting the message only of the transfer instruction and transferring the same to the middle resolution device  102 . 
     In this embodiment, after transferring, the QVGA content  122 , the access flag  164 , and the number of dummy contents  166  of the low resolution device  104  which becomes the transfer source are deleted. By the transfer to the high resolution side, the low resolution device  102  which becomes a transfer destination sets the access flag  150  to  1 , and makes the reproduction of the SDTV content  118  possible. Further, the number of dummy contents  152  is determined by the following formula.
 
(the number of dummy contents)=(the number of dummy contents of the transfer source)−1
 
     In the case of  FIG. 20B , the formula becomes as follows.
 
(the number of dummy contents)=(the number of the dummy contents of the transfer source)−1=2−1=1
 
       FIG. 21  is an explanatory drawing in the case where the content is returned to the high resolution device  100  from the middle resolution device  102 . This transfer also does not perform a substantial transfer of the content, but transfers the transfer instruction only. Further, the SDTV content  118 , an access flag  150 , and the number of dummy contents  152  of the middle resolution device  102  which becomes a transfer source are deleted. In the high resolution device  100  that has become a transfer destination, the access flag  130  is set to 1, thereby making the HDTV content  114  reproducible. Further, the number of dummy contents  132  becomes as follows:
 
(the number of dummy contents)=(the number of s of the transfer source)−1=1−1=0
 
     With respect to the number of dummy contents that is controlled by the transfer between the devices of the contents of these  FIGS. 19 and 21 , a threshold value for controlling the copy is set, so that the transfer and storage of the contents exceeding the threshold value are prohibited. For example, if the threshold value of the dummy content is set to a threshold value=2, then, as shown in  FIG. 20C , the number of the dummy contents  166  becomes 2, and further, when transferred to another device, the number of dummy contents becomes 3 so that it exceeds the threshold value, thereby the transfer and storage of the content can be prohibited. 
     As a result, the content of the same broadcast content of the low resolution transcoded from the original HDTV content  114  is prevented from being substantially stored as copy content in another device without any restriction. 
       FIGS. 12A ,  12 B and  22 C are time charts of the transfer processing of the broadcast content in  FIG. 17 . In  FIGS. 12A ,  12 B and  22 C, the high resolution device  100  receives and records the HDTV content at step S 1 , and the access flag is set to 1 at step  2 , and the dummy content is set to 0. 
     At step S 3 , when the transfer request is discriminated, at step  4 , it is transcoded into the SDTV content of the low resolution, and after that, at step S 5 , the two-way authentication and the key exchange are performed with the low resolution device  102 , and at step S 6 , the transcoded SDTV content is encrypted, and transmitted. Then, at step S 7 , the access flag is reset to 0. 
     In the middle resolution device  102 , at step S 101 , the two-way authentication and the key exchange are performed, and at step S 102 , the encrypted SDTV content is received and decoded, and then, it is stored. At step S 103 , the access flag is set to 1, and the number of dummy contents is set to 1. At step S 104 , under a condition that the access flag is set to 1, the stored SDTV content can be reproduced. 
     Next, at step S 105 , when the transfer request for the low resolution device  104  is discriminated, at step S 106 , the content is transcoded into the QVGA content of the low resolution, and after that, at step S 103 , the access flag is set to 1, and then, at step S 107 , the two-way authentication and the key exchange are performed, and at step S 108 , the QVGA content is encrypted and transmitted, and at step S 109 , the access flag is set to 0. 
     In the low resolution device  104 , the two-way authentication and the key exchange are performed, and at step S 202 , the encrypted SDTV content is received and decoded, and then, it is stored. At step S 203 , the access flag is set to 1, and the number of dummy contents is set to 2. At step S 204 , under a condition that the access flag is set to 1, the reproduction of the stored QVGA content is performed. After that, the content is returned to the middle resolution device  102  from the low resolution device  104 , and the returning of the content to the high resolution device  100  from the middle resolution device  102  is also performed according to needs. 
       FIGS. 23A and 23B  are flowcharts of the video transfer processing in the high resolution device  100  of  FIGS. 18A and 18B . The processing of steps S 1  to S 16  of  FIGS. 23A and 23B  are the same as the image transfer processing of  FIGS. 13A and 13B  except that the number of dummy contents is processed. In  FIGS. 23A and 23B , at step S 3 , after the video recording is stored, the number of dummy contents is set to 0. Further, at step S 14 , when the transfer request is made from the low resolution side, the only different point is that the number of dummy contents is set as:
 
(the number of dummy contents)=(the number of dummy contents of the transfer destination)−1.
 
       FIGS. 24 and 25  are flowcharts of the video transfer processing in the middle resolution device  102  of  FIGS. 18A and 18B . Although this video transfer processing is also basically the same as the flowchart of the video transfer processing in the low resolution device  104  shown in  FIG. 14 , it is different in that the dummy contents are determined and the dummy contents are compared with the threshold value, and if they exceed the threshold value, the transfer is prohibited. 
     Further, the middle resolution device  102  receives and stores the SDTV content transcoded from the high resolution device, and moreover, transfers the QVGA contented transcoding the SDTV content to the low resolution device  104 . 
     In  FIGS. 24A and 24B , at step S 1 , if transfer request is made from the high resolution side, at step S 2 , the encrypted content, that is, the SDTV content is received and decoded, and the, is stored, and at step S 3 , the access flag is set to 1, and the number of dummy contents is set to the value adding 1 to the number of the dummy contents of the transfer source. 
     At step S 4 , when reproduction request is made, at step S 5 , if the access flag is set to 1, at step S 6 , the stored SDTV content is read and reproduced. If the access flag is set to 0, at step S 20 , an error message is outputted, and no reproduction is made. 
     At step S 7 , when the transfer request toward the low resolution side is made, at step S 8 , whether or not the number of dummy contents reaches the threshold value is checked. If it is below the threshold value, at step S 9 , the two-way authentication and the key exchange with the device of the transfer destination are performed, and after that, the stored SDTV content is transcoded into the QVGA content being the low resolution of the transfer destination at step S 10 , and then, at step S 11 , 
     it is encrypted and transferred, and at step S 12 , the access flag is reset to 0. At step S 8 , if the number of the dummy contents reaches the threshold value, the transfer processing of the content is prohibited, and at steps S 21 , an error message is outputted, and no transfer processing is performed. 
     At step S 13 , when the transfer request of the content is made from the low resolution side, at step S 14 , the two-way authentication and the key exchange with the transfer destination de ice are performed, and the transfer processing without accompanied with the content is performed. For this return of the content, at step S 15 , the access flag is set to 1, and after that, the number of dummy contents is made into a value subtracting 1 from the content of the transfer destination. 
     Next, in  FIG. 25 , at step S 16 , when the transfer request toward the high resolution side is discriminated, at step S 17 , the two-way authentication and the key exchange with the device of the transfer destination are performed, and the transfer processing without accompanied with the content is performed. At step S 18 , the access flag is reset to 0. The processing up to this step S 18  are repeated at step S 19  until the stop instruction of the device is received. 
     Incidentally, the video transfer processing in the low resolution device  104  of  FIGS. 18A and 18B  is basically the same as the video transfer processing in the middle resolution device  102  of  FIGS. 24 and 25 , but differs in that the encrypted content received and decoded at step S 2  is the QVGA content. Further, with respect to the transfer toward the low resolution side, if the stored QVGA content is at the lowest resolution degree, the processing of steps S 7  to S 15  and S 21  are omitted. 
       FIG. 26  is a flowchart showing a dummy content count processing executed by respective processing of the high resolution device  100 , the middle resolution device  102 , and the low resolution device  104  as a sub-routine in  FIGS. 18A and 18B . In  FIG. 26 , the dummy content count processing, when the transfer from the high resolution side is discriminated at step S 1 , takes a value adding 1 to the number of dummy contents of the transfer destination as the number of dummy contents at step S 2 . Further, when the transfer from the low resolution side is discriminated at step S 3 , the processing takes a value subtracting 1 from the number of dummy contents of the transfer source as the number of dummy contents. 
       FIGS. 27 ,  28 , and  29  are explanatory drawings of the transfer processing accompanied with the resolution conversion of the broadcast content in  FIGS. 18A and 18B  that leaves the content from the low resolution side when the transfer is made to the high resolution side.  FIG. 27A  shows a state in which the HDTV content  114  is recorded and stored in the high resolution device  100 , and the access flag  130  is set to 1, and the number of dummy contents  132  is set to 0. 
       FIG. 27B  shows a case where the transfer is made from the high resolution device  100  to the middle resolution device  102 , 
     in which the HDTV content  114  is transcoded, and is stored in the middle resolution device  102  as the SDTV content  118 . In this case, the access flag  130  of the transfer source is reset to 0, and the access flag  150  of the transfer destination is set to 1. Further, the number of dummy contents of the transfer destination becomes a value adding 1 to the number of transfer source contents. 
     That is, the number of dummy contents at the transferring time from the high resolution side to the low resolution side is (the number of dummy contents)=(the number of dummy contents of the transfer source)+1, and this is the same as the case where the content of the low resolution side is deleted at the transferring time toward the high resolution side shown in  FIGS. 19 to 21 . 
       FIG. 28A  shows the transfer from the middle resolution device  102  to the low resolution device  104 , in which the SDTV content  118  is transcoded to the QVGA content  122 , and is stored in the low resolution device  104 . In this case, the access flag  150  of the transfer source is reset to 0, and the access flag  164  of the transfer destination is set to 1. Further, the number of dummy contents of the transfer destination is set to 2. 
       FIG. 28B  is an explanatory drawing in the case where the content is returned from the low resolution device  104  to the middle resolution device  102 . When the content is returned to the high resolution side, since the transcoding is not possible from the low resolution side to the high resolution side, the transfer of the content is not performed, but the transfer instruction only is transferred. 
     In this case, the QVAG content  122  is left alone in the low resolution device  104  which becomes the transfer source. 
     Further, the access flag  164  of the transfer source is reset to 0, and the access flag  150  of the transfer destination is set to 1. Further, the number of dummy contents  166  is 2, and the number of dummy contents of the transfer destination is also 2. 
     That is, the number of dummy contents when the content is left alone in the low resolution side of the transfer source is taken as (the number of dummy contents)=(the number of dummy contents of the transfer source)=2 
       FIG. 29  shows a case where the content is returned from the middle resolution device  102  to the high resolution device  100 , and in this case also, the transfer of the content is not performed, but the transfer instruction only is transferred. 
     In this case, the access flag  150  of the transfer source is reset to 0, and the access flag  130  of the transfer destination is set to 1. Further, the number of dummy contents of the transfer destination is set to: (the number of dummy contents of the transfer destination)=(the number of dummy contents of the transfer source)=2. 
     As shown in  FIGS. 27A to 29 , when the transfer of the content is made from the high resolution device  100  to the middle resolution device  102  and the low resolution device  104 , and then, is returned back again, as shown in  FIG. 28C , the values of the number of dummy contents of the dummy content counter  132 ,  152 , and  166  become 2. 
     Here, when the threshold value of the number of dummy contents is set to [2], if the content is transferred to other than the device of  FIG. 29D , the number of dummy contents becomes 3 in the device of the transfer destination, and since this exceeds the threshold value, the transfer of the content is prohibited, and the storing of more contents transcoded in another device can be prevented. 
       FIG. 30  shows a flowchart of a dummy content count processing in  FIGS. 27 to 29  as a sub routine. In FIG.  30 , at step S 1 , if the number of the dummy contents of the transfer destination is below the threshold value, at step S 2 , when the transfer from the high resolution side is discriminated, at step S 3 , the value adding 1 to the number of dummy contents of the transfer source is taken as the number of dummy contents. Further, at step S 4 , when the transfer from the low resolution side is discriminated, the number of dummy contents is left alone as it is, and is taken as the number of dummy contents. 
     On the other hand, at step S 1 , when the number of dummy contents of the transfer source exceeds the threshold value, the processing of steps S 2  to S 4  are skipped, and at step S 5 , 
     the number of dummy contents of the transfer source is taken as it is as the number of dummy contents. 
     Incidentally, in the above described embodiment, though the transcoding is performed so as to change the resolution between the devices and transfer the content, the copy transferring the content as it is without changing the resolution can be also adapted to the content management processing of the present invention by similarly setting the access flag and the number of dummy contents. 
     In this case also, even if the original copy is stored in the plurality of devices, since the device capable of reproducing the copy is only one device in which the access flag is set to 1, a copy control by once-copy can be maintained. 
     (Multiplex Codec Recording) 
       FIG. 31  is a block diagram of the functional structure of a device which receives and records the HDTV content by multiplex CODEC. In  FIG. 31 , a recording device  300  comprises a HDTV tuner  302 , a HDTV CODEC  304  of a MPEG2, a QVGA CODEC  306  of H.264, an access flag control units  308  and  310 , a broadcast content storage unit  312 , and a content reproduction unit  322 . 
     The HDTV CODEC  304  and the QVGA CODEC  306  decode a HDTV broadcast signal received by the HDTV tuner  202  under a copy control condition of once-copy in parallel by CODEC systems of the MPEG2 and the H.264, respectively, and stores it in the broadcast content storage unit  312  as a HDTV content  314  and a QVGA CONTENT  318 . 
     The access control units  308  and  310  sets the access flags  316  and  320  for the HDTV content  314  and the QVGA content  318 , respectively, and for example, the access flag  316  of the HDTV content  314  set by default is set to 1 so that the reproduction is made possible, and the QVGA content  318  is prohibited to be reproduced by resetting the access flag  320  to 0. 
     The setting state of the access flags  316  and  320  by the default is changed according to the selection of the content desired to be reproduced by the user according to needs. For example, with respect to the storage state of the default, when the user instructs the reproduction of the QVGA content  318 , its access flag  315  is set to 1, and the access flag  316  of the HDTV content  315  is reset to 0, and the content reproduction unit  322  reproduces and outputs the content at the side in which the access flag is set to 1. 
     As a result, the recording device  300  comprises two CODECS of a HDTV CODEC  304  and a QVGA CODEC  306 , and even when two contents are stored by doubly decoding the same HDTV receiving broadcast, either one of the access flag is set to 1, and the remaining access flag is set to 0, and only one broadcast content whose access flag is set to 1 can be reproduced, and therefore, even if it is the storage of plural contents by the multiplex CODEC, a restrict condition of a copy control by the copy-once can be maintained. 
       FIG. 32  is a flowchart of the multiplex CODEC processing of  FIG. 31 . At step S 1 , when a request for recording is made, at step S 2 , the access flag of the designated CODEC is set to 1, and the remaining flag is set to 0. Subsequently, at step S 3 , a recording storage processing of the multiplex CODEC is performed. At step S 4 , when a request for reproduction is made, 
     at step S 5 , the access flag is checked, and when the access flag is set to 1, at step S 7 , the reproduction of recorded content is performed. 
     When the access flag is not set to 1, at step S 6 , the corresponding access flag is set to 1, and the remaining flag is reset to 0, and after that, at step S 7 , a recorded connect whose access flag is set to 1 is reproduced. These processing of steps S 1  to S 7  are repeated at step S 8  until the stop instruction is received. 
     Incidentally, in  FIG. 31 , though an example has been cited on the case where the multiplex CODEC recording is performed by providing two sets of CODEC in the recording device  300 , the same can be also similarly adapted to the case where more than three CODECS are provided. 
     Further, the processing portion of the device that performs the processing including the encryption decoding of the broadcast content of the present invention is given a protection against an illegal access by using a hardware module or software having an anti-tamper processing function. 
     Further, the communications between the devices use encryption communications such as the IEEE1394 or the DTPC when a DVD device is connected to the personal computer by a DTCP port, and further, the encryption communications are performed by a protocol such as SSL or IPSec when the devices are mutually connected by LAN. 
     Incidentally, the present invention is not limited to the above described embodiment, and includes appropriate modifications not harming the object and advantages of the invention, and moreover, the invention is not subject to the limitation by the numerical values shown in the above described embodiment.