Abstract:
The object of the present invention is to provide contents distribution method and system which can readily distribute digital contents, can prevent unfairness such as copying and falsifying accounting data and can also correspond to the payment of a small amount. To achieve the above object, a distribution service operator encrypts contents provided by a contents provider such as newspaper articles, a magazine, music, images and software and distributes them, a user decodes and utilizes only desired contents using a user terminal that receives the above encrypted contents, accounting is executed for only utilized contents and totalization is carried out by a central station.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to contents distribution method and system, particularly relates to contents distribution method and system for enabling encrypting and distributing digital contents and secure accounting. 
   2. Description of the Related Art 
   Recently, digital contents such as newspaper articles, a magazine, music, images and software are starting to be distributed utilizing various distribution paths such as the Internet, CD-ROM and satellite communications and in the future, the distribution of digital contents is expected to be further increased. Though many of these digital contents are free, some providers of digital contents desire that in the future, the charge for the distribution of digital contents should be collected. 
   However, there are generally the following problems for a provider of digital contents to distribute digital contents subject to payment utilizing the above distribution paths and the above problems prevent digital contents subject to payment from being provided. 
   1) As distributed digital contents are unfairly copied, copyright is not protected. 
   2) An exact accounting system for digital contents is not established. 
   3) The amount of the charge for digital contents is small, for example a few tens yen or a few hundreds yen and an accounting system which can correspond to the payment of a small amount is not established. 
   4) Accounting data may be falsified. 
   5) Special hardware is required of every terminal utilizing digital contents to be paid and a user utilizing digital contents to be paid is required to considerably invest in facilities. 
   Therefore, for technique for solving the above problems, “a data broadcast system and a data sink” disclosed in Japanese Published Unexamined Patent Application No. Hei 8-32530 is proposed. In the above “data broadcast system and data sink”, a data broadcast system for encrypting and transmitting data, decoding it on the side on which the data is received and flexibly accounting according to the quantity of decoded data and others is disclosed and technique corresponding to the problems described in above 1) and 2) is disclosed. 
   For a method of paying a small amount described in above 3), many prepaid systems in which a prepaid card is used are proposed. 
   However, in the above “data broadcast system and data sink” disclosed in Japanese Published Unexamined Patent Application No. Hei 8-32530, there are problems that a key for decoding is required to be prepared every data type and that there is no measure for falsifying accounting data. 
   In the meantime, in the above prepaid system which is a method of paying a small amount, a receipt for individual digital contents is not issued, purchase is required to be managed on his/her own responsibility and use in an office and others is unsuitable. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is provide a contents distribution method and a contents distribution system wherein the distribution of digital contents is facilitated and unfairness such as copying and falsifying accounting data is prevented and which can also correspond to the payment of a small amount. 
   To achieve the above object, a first invention is based upon a contents distribution method for distributing digitized contents to plural users and is characterized in that contents are encrypted and distributed, a user decodes and utilizes the encrypted contents, and accounting is executed according to the utilized contents. 
   A second invention is based upon the first invention and is characterized in that in the above distribution, information showing the summary of the above encrypted contents is attached to the encrypted contents. 
   A third invention is based upon the second invention and is characterized in that only in case the above summary information is accompanied by decoding information for decoding the encrypted contents corresponding to the summary information, the summary information is displayed. 
   A fourth invention is based upon the first invention and is characterized in that the above decoding is executed based upon a decoding key generated based upon first decoding information attached to the above encrypted contents and second decoding information with which the above user is provided. 
   A fifth invention is based upon the first invention and is characterized in that the above contents mean a document displayed or printed in page units and the above accounting is executed for the page units. 
   A sixth invention is based upon the first invention and is characterized in that the above distribution is made by a broadcast. 
   A seventh invention is based upon a contents distribution system for distributing digitized contents to plural users and is characterized in that a distribution device for distributing encrypted contents, a user terminal for receiving the encrypted contents distributed by the above distribution device and generating accounting information according to the utilization of the encrypted contents received and a central station for collecting and totalizing accounting information generated by the above user terminal are provided. 
   An eighth invention is based upon the seventh invention and is characterized in that the above distribution device encrypts contents provided by a contents provider, generates encrypted contents, attaches list information showing the contents of the encrypted contents and summary information showing the summary to the above encrypted contents and distributes the above encrypted contents. 
   A ninth invention is based upon the eighth invention and is characterized in that the above user terminal displays the above list information and the above summary information and decodes only encrypted contents selected by a user based upon the above displayed list information and summary information out of the above received encrypted contents. 
   A tenth invention is based upon the eighth or ninth invention and is characterized in that the above user terminal displays only list information and summary information respectively corresponding to encrypted contents accompanied by decoding information out of the above list information and the above summary information. 
   An eleventh invention is based upon the seventh invention and is characterized in that the above distribution device distributes the above encrypted contents by a broadcast. 
   A twelfth invention is based upon the seventh invention and is characterized in that the above user terminal is provided with a data sink for receiving encrypted contents distributed from the above distribution device, a data output part for storing the encrypted contents received by the above data sink, decoding the encrypted contents stored, and generating accounting information according to the quantity of the decoded contents and a printer for printing the contents decoded by the data output part. 
   A thirteenth invention is based upon the twelfth invention and is characterized in that the above quantity of the utilized contents means the number of pages included in contents printed by the above printer. 
   A fourteenth invention is based upon the seventh invention and is characterized in that the above user terminal is provided with a data sink for receiving encrypted contents distributed from the above distribution device and a display for storing the encrypted contents received by the above data sink, decoding and displaying the encrypted contents stored, and generating accounting information according to the number of pages included in the displayed contents. 
   A fifteenth invention is based upon the seventh invention and is characterized in that the above distribution device distributes the above encrypted contents to which first decoding information required for decoding the encrypted contents is attached and in that the above user terminal decodes the above encrypted contents based upon the above first decoding information and second decoding information intrinsic to a user using the above user terminal. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing an example of the configuration of a contents distribution system according to the present invention; 
       FIG. 2  shows the configuration of tickets; 
       FIG. 3  explains the packaging of contents; 
       FIG. 4  is a block diagram showing the configuration of a user terminal  4 ; 
       FIG. 5  is a block diagram showing the configuration of a data sink  41 ; 
       FIG. 6  is a flowchart showing the flow of the operation of the data sink  41 ; 
       FIG. 7  explains unpacking; 
       FIG. 8  is a block diagram showing the configuration of a data output device  42 ; 
       FIG. 9  is a flowchart showing the flow of list display processing; 
       FIG. 10  is a flowchart showing the flow of the output processing of contents; 
       FIG. 11  shows the items of accounting information; 
       FIG. 12  shows a concrete example of accounting information; 
       FIG. 13  is a block diagram showing the configuration of a display  44 ; 
       FIG. 14  is a flowchart showing the flow of the display processing of contents; 
       FIG. 15  is a flowchart showing the flow of the processing of accounting information in the data output device  42 ; 
       FIG. 16  is a block diagram showing the configuration of a central station  5 ; 
       FIG. 17  is a flowchart showing the flow of accounting information totalizing processing; and 
       FIG. 18  shows an example of the output of the totalized result. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to attached drawings, an embodiment of a contents distribution method and a contents distribution system respectively according to the present invention will be described in detail below. 
     FIG. 1  is a block diagram showing an example of the configuration of a contents distribution system according to the present invention. 
   As shown in  FIG. 1 , the contents distribution system is provided with contents providers  1 - 1  and  1 - 2 , a distribution service operator  2 , a satellite  3 , user terminals  4 - 1  to  4 - 3 , a central station  5 , a satellite line  6  and a public line  7 . The contents providers  1 - 1  and  1 - 2  mean the providers of digital contents such as newspaper articles, a magazine, music, images and software and the distribution service operator  2  encrypts contents provided by the contents providers  1 - 1  and  1 - 2  and distributes them to user terminals  4 - 1  to  4 - 3  via the satellite line  6  utilizing the satellite  3 . The user terminals  4 - 1  to  4 - 3  decodes contents distributed to each, displays and prints them, the central station  5  collects accounting data from the user terminals  4 - 1  to  4 - 3  via the public line  7  and manages it. 
   In the example of the configuration shown in  FIG. 1 , contents are distributed via the satellite line  6 , however, contents may also be distributed via a network such as the Internet or utilizing media such as CD-ROM. 
   The contents provider  1  ( 1 - 1  and  1 - 2 ), the distribution service operator  2 , the user terminal  4  ( 4 - 1 ,  4 - 2  and  4 - 3 ) and the central station  5  respectively composing the contents distribution system will be described below. 
   [1] Contents Provider 
   The contents provider  1  means a provider of digital contents such as newspaper articles, a magazine, music, images and software, and here, the contents provider  1 - 1  is a publisher M and the contents provider  1 - 2  is a newspaper publishing company N. In this case, contents provided by each company include an electronic magazine and electronic newspaper articles. 
   [2] Distribution Service Operator 
   The distribution service operator  2  receives contents from each contents provider and generates contents related information such as an icon file and the summary based upon the contents. Next, the distribution service operator encrypts each content and issues a ticket for the encrypted contents. 
   For the type of an issued ticket, there area signed ticket  10  and an unsigned ticket  20  respectively shown in  FIG. 2 , the signed ticket  10  is composed of decoding key information  11 , contents ID  12 , provider ID  13 , points/page  14  and the number of pages  15  and the unsigned ticket  20  is composed of decoding key information  21 , contents ID  22 , provider ID  23 , points/page  24  and the number of pages  25 . The decoding key information  11  in the signed ticket  10  is customized for a specific user and the decoding key information  12  in the unsigned ticket  20  is customized for all users. For example, if the signed ticket  10  is issued so that only a user A (the user terminal  4 - 1 ) can utilize the contents N 1  of the newspaper publishing company N (the contents provider  1 - 2 ), a decoding key for decoding the contents N 1  is calculated based upon the decoding key information  11  and intrinsic information described later with which the user A is provided. If the unsigned ticket  20  is issued so that the user A (the user terminal  4 - 1 ), a user B (the user terminal  4 - 2 ) and a user C (the user terminal  4 - 3 ) which are respectively all users can utilize the contents M 1  of the publisher M (the contents provider  1 - 1 ), a decoding key for decoding the contents M 1  is calculated based upon the decoding key information  21  and information common to all users described later. 
   The distribution service operator  2  generates the configuration information of a contents list when the distribution service operator finishes the issue of a ticket and packages each contents, contents related information, contents list configuration information and tickets. For example, as shown in  FIG. 3 , contents ( 1 ) folder  32 - 1  to contents (n) folder  32 - n  and a ticket folder  33  are stored in Pack ( 1 ) folder  31  and are packaged together with list configuration information  34  in a package ( 1 )  35 . An icon ( 1 )  36 - 1  which is contents related information, the summary ( 1 )  37 - 1  and encrypted contents ( 1 )  38 - 1  which are the body of the contents are stored in the contents ( 1 ) folder  32 - 1 , and a ticket ( 1 )  39 - 1  to a ticket (n)  39 - n  are stored in the ticket folder  33 . 
   Next, the distribution service operator  2  broadcasts the packaged contents to each user (the user terminals  4 - 1  to  4 - 3 ) according to a distribution schedule. 
   The distribution service operator  2  may only distribute contents and in this case, the contents provider  1  ( 1 - 1  and  1 - 2 ) executes a series of operation up to packaging. 
   [3] User Terminal 
   Next, the user terminal  4  ( 4 - 1  to  4 - 3 ) will be described. 
     FIG. 4  is a block diagram showing the configuration of the user terminal  4 . 
   As shown in  FIG. 4 , the user terminal  4  is composed of a data sink  41 , a data output device  42 , a printer  43 , displays  44 - 1  to  44 - 3  and a network  45 . 
   The data sink  41  receives contents distributed by the distribution service operator  2 , the data output device  42  stores contents received by the data sink  41  and outputs contents at the request of a user. The printer  43  and the displays  44  ( 44 - 1  to  44 - 3 ) respectively prints and display contents at the request of a user. 
   The details of each unit composing the user terminal  4  will be described below. 
   [3-1] Data Sink 
     FIG. 5  is a block diagram showing the configuration of the data sink  41 . 
   The data sink  41  is composed of a data receiving antenna  411 , a data reception control unit  412 , a retransmission request transmitter  413 , a data storage  414  and a unpacking unit  415 . 
   The data receiving antenna  411  receives distributed data and the data reception control unit  412  controls the reception of data. The retransmission request transmitter  413  requests the distribution service operator  2  to retransmit data via the public line  7  and others if an error occurs in reception. The data storage  414  stores received data and a package acquired by packaging the data, and the unpacking unit  415  unpacks received data stored in the data storage  414 . 
     FIG. 6  is a flowchart showing the flow of the operation of the data sink  41 . 
   In the data sink  41 , when operation is started in a step  1001 , the data receiving antenna  411  receives data distributed by the distribution service operator  2  in a step  1002 , the data reception control unit  412  stores the received data in the data storage  414  in a step  1004  if no error occurs in reception (NO in a step  1003 ) and repeats the above processing (in the steps  1002  to  1004 ) (No in a step  1005 ) until reception is finished. 
   When reception is finished (YES in the step  1005 ), the unpacking unit  415  unpacks data stored in the data storage  414  in a step  1006  and stores unpacked data in the data storage  414  in a step  1007 . Afterward, the unpacked data stored in the data storage  414  is transferred to the data output device  42  in a step  1008  and the processing is terminated in a step  1010 . 
   In the meantime, if an error occurs in data received by the data receiving antenna  411  (YES in the step  1003 ), the retransmission request transmitter  413  requests the distribution service operator  2  to retransmit data via the public line  7  and others in a step  1009  and the processing is terminated in the step  1010 . 
   As for the processing executed by the unpacking unit  415  in the step  1006 , as shown in  FIG. 7 , the package ( 1 )  35  is expanded into list configuration information  34  and Pack ( 1 ) folder  31 . The contents ( 1 ) folder  32 - 1  to the contents (n) folder  32 - n  and the ticket folder  33  are stored in the Pack ( 1 ) folder  31 , the icon ( 1 )  36 - 1  which is contents related information, the summary ( 1 )  37 - 1  and encrypted contents ( 1 )  38 - 1  which are the body of the contents are stored in the contents ( 1 ) folder  32 - 1 , and the ticket ( 1 )  39 - 1  to the ticket (n)  39 - n  are stored in the ticket folder  33 . 
   [3-2] Data Output Device 
     FIG. 8  is a block diagram showing the configuration of the data output device  42 . 
   The data output device  42  is composed of a data sink  421 , a ticket storage  422 , a data storage  423 , a token  424 , a list display  425 , an access input unit  426 , a system controller  427 , an access control unit  428 , a decoder  429 , an output controller  430 , an accounting information processor  431 , an accounting information transmitter  432  and an accounting information transmission instruction processing unit  433 . 
   The data sink  421  receives data transferred from the data sink  41 , the ticket storage  422  stores the ticket  39  ( 39 - 1  to  39 - n  shown in  FIG. 7 ) of the data received by the data sink  421  and the data storage  423  stores list configuration information  34  and the contents folder  32  (the contents folder ( 1 )  32 - 1  to the contents folder (n)  32 - n ). 
   The token  424  includes various information such as ID  424   a , user unique identifying information  424   b , common information  424   c  and accounting information in an accounting information recorder  424   d  and is composed by an IC card for example. 
   The list display  425  displays a list of contents based upon the list configuration information  34  stored in the data storage  423  on a monitor not shown. The access input unit  426  is an interface for a user to input desired contents and its output information (paper size, the number of pages printed on one sheet, the number of pages and others) based upon the list of contents displayed on the list display  425  and is composed by a touch panel and others. The system controller  427  operates each element of the data output device  42  and controls access, decoding processing, accounting information processing and others. The access input unit  426  is equivalent to a keyboard and a mouse in case a personal computer and others are used for the data output device  42  and is equivalent to a touch panel in case the printer  43  is provided with a control panel such as a touch panel. 
   The access control unit  428  checks access to the encrypted contents  38  stored in the data storage  423  based upon each information stored in the token  424  and the decoding key information of a ticket and the decoder  429  decodes the encrypted contents  38  based upon the ticket  39  stored in the ticket storage  422  and the user unique identifying information  424   b  or the common information  424   c  in the token  424 . 
   The output controller  430  outputs the contents decoded by the decoder  429  to the printer  43  according to output information input from the access input unit  426 , the accounting information processor  431  acquires accounting information from each unit after the output of the contents and records it in the accounting information recorder  424   d  in the token  424 . In this case, it is described that the accounting information recorder  424   d  is in the token  42 , however, the accounting information recorder  424   d  may also be on a record medium such as a hard disk not shown with which the user terminal  4  is provided. 
   The accounting information transmitter  432  transmits accounting information recorded in the accounting information recorder  424   d  to the central station  5  via the public line  7  and others (or sends the token of an IC card and portable media such as a floppy disk by mail) and the accounting information transmission instruction processing unit  433  instructs the accounting information transmitter  432  to transmit accounting information according to a preset schedule and others. 
   Referring to  FIG. 9 , list display processing for displaying a list of contents will be described below. The list display  425  can select contents the list of which can be displayed depending upon whether a ticket is stored in the ticket storage  422  or not. 
     FIG. 9  is a flowchart showing the flow of list display processing. 
   When list display processing is started in a step  1101  and data is transferred from the data sink  41  (YES in a step  1102 ), the data sink  421  receives the data in a step  1103 , stores the ticket  39  ( 39 - 1  to  39 - n ) in the ticket folder  33  of the received data in the ticket storage  422  in a step  1104  and stores the icon  36 , the summary  37  and the encrypted contents  38  respectively in the contents folder  32  and the list configuration information  34  in the data storage  423  in a step  1105 . Next, when a request for displaying a list of contents is input from the access input unit  426  (YES in a step  1106 ), the list display  425  acquires ID of displayed contents based upon the list configuration information  34  in a step  1107 . 
   If contents ID is acquired (YES in a step  1108 ), the list display  425  requests the access control unit  428  to check whether a ticket corresponding to the acquired contents ID exists or not in a step  1109 . The access control unit  428  inquires of the ticket storage  422  whether the ticket corresponding to the contents ID exists or not in a step  1110 . 
   If the ticket is an unsigned ticket  20  (YES in a step  1111 ) in case the ticket is stored in the ticket storage  422  (YES in the step  1110 ), the list display  425  is informed that the list can be displayed and the list display  425  displays the list in a step  1112 . 
   In the meantime, as the following ticket is a signed ticket  10  if a ticket stored in the ticket storage  422  is not an unsigned ticket  20  (NO in the step  1111 ), the access control unit  428  acquires user unique identifying information  424   b  from the token  424  and calculates whether the decoding key information  11  of the signed ticket  10  is customized for the user unique identifying information  424   b  or not in a step  1113 . As a result of calculation, if the decoding key information  11  is customized for the user unique identifying information  424   b  (YES in a step  1114 ), the list display  425  is informed that the list can be displayed, the list display  425  displays the list in a step  1112  and if the decoding key information  11  is not customized for the user unique identifying information  424   b  (No in the step  1114 ), the list display  425  acquires the next contents ID based upon the list configuration information  34  without displaying in a step  1107 . 
   Processing after the step  1107  is repeated as long as the acquisition of contents ID succeeds (YES in the step  1108 ) and when the acquisition of contents ID fails, that is, processing for all contents IDs is finished (NO in the step  1108 ), the list display processing is terminated in a step  1115 . 
   When a list is displayed, the icon  36  and the summary  37  respectively stored in the data storage  423  are displayed at the request of a user or if necessary. When the icon  36  is selected using a touch panel, a mouse or a keyboard, the corresponding contents are selected, the summary  37  shows the summary, the table and others of the corresponding contents and a user utilizes the icon and the summary to select contents and required pages in contents. 
   Next, referring to  FIG. 10 , the output processing of contents will be described. 
     FIG. 10  is a flowchart showing the flow of the output processing of contents. 
   When a request for the output of contents is input from the access input unit  426 , the output processing of contents is started in a step  1201 , when a user selects contents from the access input unit  426  (YES in a step  1202 ) and output information is input (YES in a step  1203 ), the access control unit  428  checks whether the token  424  exists or not and its legitimacy and checks whether the ticket  39  corresponding to the selected contents is stored in the ticket storage  422  or not and whether the ticket is falsified or not, that is, whether access to the selected contents is authorized or not in a step  1204 . 
   As a result of checking whether the access is authorized or not, if the access is not authorized (NO in a step  1205 ), the system controller  427  instructs the monitor to display information showing access is not authorized in a step  1206  and terminates the output processing of contents in a step  1212 . 
   In the meantime, as a result of checking whether access is authorized or not, if access is authorized (YES in the step  1205 ), the decoder  429  generates a decoding key based upon the ticket  39  corresponding to the selected contents and information (the user unique identifying information  424   b  in case the ticket is a signed ticket and the common information  424   c  in case the ticket is an unsigned ticket) in the token  424  and decodes the encrypted contents  38  in a step  1207 . 
   If decoding fails (NO in the step  1208 ), the system controller  427  instructs the monitor to display decoding failure information in a step  1209  and terminates the output processing of contents in the step  1212 . 
   If decoding succeeds (YES in the step  1208 ), the output controller  430  outputs decoded contents to the printer  43  according to output information in a step  1210 , the accounting information processor  431  generates accounting information based upon the used ticket  39 , the encrypted contents  38 , output information, the result of output and others, records it in the accounting information recorder  424   d  in a step  1211  and terminates the output processing of contents in the step  1212 . 
   As described above, accounting information is generated only in case the output of contents succeeds and is not generated, that is, accounting is not executed if decoding fails. If printing fails halfway even if decoding succeeds, accounting is executed only for the number of pages of output contents. 
   Accounting information is composed of “ID”, “contents ID”, “provider ID”, “date”, “number of pages included in contents”, “printed number”, “number of pages printed on one sheet and paper size”, “points per page”, “user ID” and “termination status” respectively shown in  FIG. 11 . 
   “ID” means ID for identifying accounting issued by the accounting information processor  431  and “contents ID” means ID acquired from the ticket  39  of utilized contents. “Provider ID” means ID acquired from the ticket  39  of a contents provider that provides utilized contents and “date” means a date when contents issued by the system controller  427  are utilized. “Contents total page number” means the number of pages acquired from the ticket  39  and included in contents requested to be output and “printed number” is information showing the number of sheets acquired from the output controller  430  and actually printed by the printer  43 . “Number of pages printed on one sheet, paper size” is information showing the number of pages acquired from the output controller  430  and printed on one sheet, the size and the direction of printing paper and “points per page” is information showing the number of points or a price per page acquired from the ticket  39 . “User ID” means ID acquired from ID  424   a  in the token  424  of a user that utilizes contents and “termination status” means information including error information in case the result of output from the output controller  430  is abnormal output and is acquired from the system controller  427 . 
   Accounting information generated under these items is normally added every time contents are output as plural accounting information as shown in  FIG. 12 , is stored in the accounting information recorder  424   d  and is transmitted to the central station  5  according to a predetermined schedule and others. As accounting information may be falsified while it is transmitted to the central station  5 , security such as digital signature may also be applied to accounting information. 
   [3-3] Printer 
   For the printer  43 , a printer heretofore used and a compound device that simultaneously functions as a printer, a copying machine and a facsimile are used. Therefore, the description of the printer  43  is omitted. 
   [3-4] Display 
     FIG. 13  is a block diagram showing the configuration of the display  44  ( 44 - 1  to  44 - 3 ). 
   The display  44  is composed of a data transmitter-receiver  441 , a ticket storage  442 , a data storage  443 , a display  444 , an access input unit  445 , a system controller  446 , an access control unit  447 , a decoder  448  and an accounting information processor  449 . 
   The data transmitter-receiver  441  is connected to the data sink  41  and the data output device  42  via the network  45 , receives data transferred from the data sink  41 , receives and transmits data from/to the data output device  42 . The ticket storage  442  stores the ticket  39  ( 39 - 1  to  39 - n  shown in  FIG. 7 ) of data received by the data transmitter-receiver  441  and the data storage  443  stores list configuration information  34  and a contents folder  32  (contents folder ( 1 )  32 - 1  to contents folder (n)  32 - n ). 
   The display  444  displays a list of contents on a monitor not shown based upon the list configuration information  34  stored in the data storage  443  and also displays contents. The access input unit  445  is an interface for a user to input desired contents and its output information such as paper size, the number of pages printed on one sheet and the number of pages based upon the list of contents displayed by the display  444  and is composed by a touch panel and others. The system controller  446  operates each unit of the display  44  and controls access, decoding, accounting information processing and others. 
   The access control unit  447  checks access to the encrypted contents  38  stored in the data storage  443  based upon each information item stored in the token  424  of the data output device  42  and the decoder  448  decodes the encrypted contents  38  based upon the ticket  39  stored in the ticket storage  442  and user unique identifying information  424   b  or common information  424   c  in the token  424 . The accounting information processor  449  acquires accounting information from each unit after the utilization of contents and records it in the accounting information recorder  424   d  in the token  424 . 
   Referring to  FIG. 14 , the display processing of contents will be described below. 
     FIG. 14  is a flowchart showing the flow of the display processing of contents. 
   When a request for displaying contents is input from the access input unit  445 , the display processing of contents is started in a step  1301 , when a user selects contents via the access input unit  445  (YES in a step  1302 ) and inputs output information (YES in a step  1303 ), the access control unit  447  checks whether the token  424  exists or not and its legitimacy via the data transmitter-receiver  441 , checks whether the ticket  39  corresponding to the selected contents is stored in the ticket storage  442  or not and checks whether the ticket  39  is falsified or not, that is, whether access to the selected contents is authorized or not in a step  1304 . 
   As a result of checking whether the access is authorized or not, if the access is not authorized (NO in a step  1305 ), the system controller  447  instructs the display  444  to display information showing the access is not authorized in a step  1306  and terminates the display processing of the contents in a step  1313 . 
   In the meantime, as a result of checking whether access is authorized or not, if the access is authorized (YES in the step  1305 ), the decoder  448  generates a decoding key based upon the ticket  39  corresponding to the selected contents and information in the token  424  (user unique identifying information  424   b  in case the ticket is a signed ticket and common information  424   c  in case the ticket is an unsigned ticket) and decodes the encrypted contents  38  in a step  1307 . 
   If decoding fails (NO in a step  1308 ), the system controller  446  instructs the display  444  to display information showing that decoding fails in a step  1309  and terminates the display processing of the contents in the step  1313 . 
   If decoding succeeds (YES in the step  1308 ), the system controller  446  instructs the display  444  to display the decoded contents according to output information in a step  1310 , the accounting information processor  449  generates accounting information based upon the used ticket  39 , the encrypted contents  38 , output information, the result of output and others in a step  1311 , transmits the accounting information to the data output device  42  via the data transmitter-receiver  441  in a step  1312  and terminates the display processing of the contents in the step  1313 . 
   Next, referring to  FIG. 15 , the processing of accounting information transferred from the display  44  to the data output device  42  will be described. 
     FIG. 15  is a flowchart showing the flow of the processing of accounting information in the data output device  42 . 
   When the data output device  42  starts processing in a step  1401  and receives accounting information from the display  44  in a step  1402 , the system controller  427  instructs the accounting information processor  431  to record accounting information, the accounting information processor  431  records the received accounting information in the accounting information recorder  424   d  in a step  1403  and terminates accounting information processing in a step  1404 . 
   As described above, the display  44  decodes and displays contents encrypted in each device. Therefore, as contents flow on the network  45  with the contents encrypted, the unfair copying of contents in the network  45  can be prevented. 
   [4] Central Station 
   Next, the central station  5  will be described. 
     FIG. 16  is a block diagram showing the configuration of the central station  5 . 
   As shown in  FIG. 16 , the central station  5  is composed of an accounting information receiver  51 , an accounting information storage  52 , a total setting unit  53 , an accounting information totalizing unit  54  and a totalized result output unit  55 . The accounting information receiver  51  receives accounting information transmitted from the data output device  42  of the user terminal  4  via the public line  7  and others, the accounting information storage  52  classifies and stores accounting information received by the accounting information receiver  51  for every user. The total setting unit  53  specifies totalized accounting information, the output destination of the totalized result and a totalizing format and others. The accounting information totalizing unit  54  totalizes accounting information stored in the accounting information storage  52  according to a condition specified by the total setting unit  53  and the totalized result output unit  55  outputs accounting information totalized by the accounting information totalizing unit  54  to a file and instructs the printer to print it. 
   Referring to  FIG. 17 , processing for totalizing accounting information will be described below. 
     FIG. 17  is a flowchart showing the flow of accounting information totalizing processing. 
   When the central station  5  starts operation in a step  1501  and the accounting information receiver  51  receives accounting information (YES in a step  1502 ), the received accounting information is stored in the accounting information storage  52  for every user, that is, for every data output device  42  in a step  1503 . Accounting information is stored every time accounting information is received at timing set by the total setting unit  53  or until totalizing is started by an instruction by a person in charge of totalizing (NO in a step  1504 ). 
   When the start of totalizing is instructed (YES in the step  1504 ) at timing set by the total setting unit  53  or by the instruction by the person in charge of totalizing, the accounting information totalizing unit  54  totalizes accounting information stored in the accounting information storage  52  according to a condition set by the total setting unit  53  in a step  1505 , the totalized result output unit  55  outputs the totalized result in a step  1506  and terminates accounting information totalizing processing in a step  1507 . 
   Next, an example of totalizing by the accounting information totalizing unit  54  will be described. 
   In totalizing, first, information in “printed number”, “number of pages printed on one sheet”, “contents total-page number” and “points per page” in accounting information is acquired. 
   Next, the number of pages included in actually utilized contents will be calculated. In the above calculation, if a value acquired by multiplying “printed number” and “number of pages printed on one sheet”, that is, “printed number×N” is larger than “contents total page number”, the number of pages included in actually utilized contents is regarded as equal to “contents total page number” and if “printed number×N” is smaller than “contents total page number”, the number of pages included in actually utilized contents is regarded as “printed number×N”. 
   Next, the number of points is calculated, detailedly, is calculated by “the number of points per page×the number of pages included in actually utilized contents” based upon “points per page”. 
   For an actual example of calculation, if a printed number is 3, the number of pages printed on one sheet is 2, a contents total page number is 5, points per page are 2 as an example 1, the number of pages included in actually utilized contents is 5 (3×2&gt;5) and the number of points is 10 (2×5). 
   Also as an example 2, if a printed number is 3, the number of pages printed on one sheet is 2, a contents total page number is 6 and points per page are 2, the number of pages included in actually utilized contents is 6 (3×2=6) and the number of points is 12 (2×6). 
   Further, as an example 3, if a printed number is 1, the number of pages printed on one sheet is 2, a contents total page number is 3, points per page are 2, the number of pages included in actually utilized contents is 2 (1×2&lt;3) and the number of points is 4 (2×2). 
   The information of totalization calculated as described above is output in a file or printed out as a list from the totalized result output unit  55  as shown in  FIG. 18 . 
   In the above embodiment, as for the display  44 , a case where plural displays are connected to the data sink  41  and the data output device  42  via the network  45  is described, however, plural displays  44  are not necessarily required to be connected and if no more than one display is utilized, the network  45  is not required. One computer can also function as the display  44  and the data output device  42  and if the Internet and media such as CD-ROM are used on a path through which contents are distributed, the same computer can also function as the data sink  41 . Further, some printers and some copying machines used for the printer  43  transfer accounting information using a public line, however, the system according to the present invention can also be composed utilizing the above device for transferring accounting information. 
   As described above, according to the present invention, as contents such as newspaper articles, a magazine, music, images and software are encrypted and distributed, a user who receives the encrypted contents decodes only desired contents and utilizes them and only the utilized contents are charged, so copyright on the side of a contents provider can be protected and a user can pay according to the quantity of utilized contents. Accounting information can be safely and readily recorded, collected and totalized. 
   As encrypted contents are decoded utilizing a ticket sent together with the contents and information in a token which a user has, different data is not required to be distributed for every user terminal which is a destination of distribution and a broadcast is allowed.