Abstract:
An information processing apparatus utilizing encrypted information corresponding to content of purchased right, includes a memory for storing the encrypted information, usage control policy indicating content of purchased right and price tag for specifying price content corresponding to the content of the purchased right. A first generating device generates a usage control status including the purchase history of the information on the basis of the usage control policy and the price tag stored in the memory. A setting device sets usage history based on usage of the information to the usage control status. A second generating device calculates an accounting price and generates accounting information including the accounting price based on the purchase history or the usage history, and/or puts a limit on purchasable usage conditions based on the purchase history or the usage history on the occasion the right is purchased again on different format from the control policy.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This patent application is a continuation of U.S. application Ser. No. 09/607,692, filed on Jun. 30, 2000 now abandoned, the disclosure of which is herein incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an information processing apparatus and method and a distribution medium and particularly to an information processing apparatus and method and a distribution medium for utilizing the encrypted information. 
   2. Description of the Related Art 
   There is provided a system in which information (content) such as a music program is encrypted and is then transmitted to an information processing apparatus of a user who has become a subscriber by signing the predetermined contract and thereby a user can utilize the content through the decoding thereof with such information processing apparatus. 
   In the information processing apparatus of the related art, it has been impossible, for example, to purchase again the content in the price based on the purchase history of such content. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the present invention, the information processing apparatus comprises memory means for storing the encrypted information, usage control policy indicating content of purchased right and price tag for specifying price content corresponding to the content of the purchased right, first generating means for generating usage control status including purchase history of the information on the basis of the usage control policy and the price tag being stored in the memory means, setting means for setting usage history based on usage of the information to the usage control status, and second generating means for, on the occasion of purchasing the right again, calculating an accounting price and generating accounting information including the accounting price based on the purchase history or the usage history and/or putting a limit on purchasable usage conditions based on the purchase history or the usage history. 
   According to another aspect of the present invention, the information processing method comprises a storing step for storing the encrypted information, usage control policy indicating content of the purchased right and price tag for specifying price content corresponding to content of the right, a first generating step for generating the usage control status including purchase history of the information based on the usage control policy and the price tag stored in the storing step, a setting step for setting usage history based on usage of the information to the usage control status, and a second generating step for, on the occasion of purchasing the right again, calculating an accounting price and generating accounting information including the accounting price based on the purchase history or the usage history and/or putting a limit on purchasable usage conditions based on the purchase history or the usage history 
   According to another aspect of the present invention, a distribution medium provides a computer-readable program making an information processing apparatus, which utilizes the encrypted information through decoding thereof corresponding to content of purchased right, execute the processes, comprising a storing step for storing the encrypted information, usage control policy indicating content of the purchased right and price tag for specifying price content corresponding to content of the right, a first generating step for generating the usage control status including purchase history of the information based on the usage control policy and the price tag stored in the storing step, a setting step for setting usage history based on usage of the information to the usage control status, and a second generating step for, on the occasion of purchasing the right again, calculating an accounting price and generating accounting information including the accounting price based on the purchase history or the usage history and/or putting a limit on purchasable usage conditions based on the purchase history or the usage history. 
   According to still another aspect of the present invention, in the information processing apparatus, information processing method and distribution medium described, the encrypted information, usage control policy indicating content of right to be purchased and price tag for specifying price content corresponding to content of right are stored, the usage control status including information purchase history is generated on the basis of stored usage control policy and price tag, the usage history based on usage of information is set to the usage control status, and on the occasion of purchasing the right again, the accounting price is calculated and the accounting information including the accounting price is also generated based on the purchase history or usage history and/or a limit on purchasable usage conditions is put based on the purchase history or usage history. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagram for explaining the EMD system. 
       FIG. 2  is a diagram for explaining the flow of main information in the EMD system. 
       FIG. 3  is a block diagram illustrating the functional structure of the EMD service center  1 . 
       FIG. 4  is a block diagram illustrating an example of functional structure of the content provider  2 . 
       FIG. 5  is a diagram illustrating an example of UCP. 
       FIG. 6  is a diagram illustrating an example of the content provider secure container. 
       FIG. 7  is a diagram illustrating an example of the certificate of the content provider  2 . 
       FIG. 8  is a block diagram illustrating a functional structure of the service provider  3 . 
       FIGS. 9A and 9B  are diagrams illustrating an example of PT. 
       FIG. 10  is a diagram illustrating an example of the service provide secure container. 
       FIG. 11  is a diagram illustrating an example of the certificate of the service provider  3 . 
       FIG. 12  is a block diagram illustrating an example of functional structure of receiver  50  of user home network  5 . 
       FIG. 13  is a diagram illustrating an example of UCS. 
       FIG. 14  is a diagram illustrating an example of accounting information. 
       FIG. 15  is a block diagram illustrating an example of functional structure of SAM 51  of the receiver  50 . 
       FIG. 16  is a flowchart for explaining the content purchase process. 
       FIG. 17  is a diagram illustrating another example of the service provider secure container. 
       FIG. 18  is a diagram illustrating another example of UCP. 
       FIG. 19  is a diagram illustrating another example of PT. 
       FIG. 20  is a diagram illustrating another example of UCS. 
       FIG. 21  is a diagram illustrating the other example of UCS. 
       FIG. 22  is a flow chart for explaining the content usage process. 
       FIG. 23  is a diagram illustrating the other example of UCS. 
       FIG. 24  is a diagram illustrating the other example of UCP. 
       FIGS. 25A and 25B  are diagrams illustrating the other example of PT. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a diagram for explaining the EMD (Electronic Music Distribution) system to which the present invention is applied. The EMD system is composed of an EMD service center  1  provided for management of each apparatus, a content provider  2  for distributing the content, a service provider  3  for providing the predetermined service corresponding to the content and a user home network  5  consisting of an apparatus (a receiver  50 , in this case) for utilizing the content. 
   Content to be distributed (provided) to the apparatus (for example, a receiver  50 ) registered to the EMD system is a digital data in which information itself has the worth. In this embodiment, one content corresponds to the music data of one music program. Content is distributed to users in unit one content (single format) or in unit of a plurality of contents (album format). A user purchases the content (actually, purchases the right of utilizing the content) and thereby the user can reproduce and duplicate the contents. 
   The EMD service center  1  transmits, as illustrated in  FIG. 2  indicating the main flow of information in the EMD system, the distribution key Kd required to utilize the content to a user home network  5  and a content provider  2 . The EMD service center  1  also receives the accounting information or the like from the apparatus of user home network  5  to adjust the usage accounting. 
   The content provider  2  holds the content to be distributed (encrypted with the content key Kco), content key Kco required to decode the content (encrypted with the distribution key Kd) and usage control policy indicating usage content of such content (hereinafter referred to as USP (Usage Control Policy)) and then supplies these data to the service provider  3  in the form called the content provider secure container (explained later). 
   The service provider  3  generates one or a plurality of price tags (PT) and holds these data. The service provider  3  transmits the generated PT to the user hole network  5  via the network  4  formed of an exclusive cable network, Internet or satellite communication in the form called the service provider secure container together with the content supplied from the content provider  2  (encrypted with the content key Kco), content key Kco (encrypted with the distribution key Kd) and UCP. 
   The user home network  5  generates the usage control status based on the UCP and PT supplied and executes the process to use the content based on the generated UCS. The user home network  5  also generates the accounting information in the timing to generate UCS and transmits this information to the EMD service center  1  together with the corresponding UCP and PT in the timing to receive the supply, for example, of the distribution key Kd. 
     FIG. 3  is a block diagram illustrating the functional structure of the EMD service center  1 . A service provider management section  11  supplies profit distribution information to the service provider  3 . A content provider management section  12  transmits the distribution key Kd or supplies the profit distribution information to the content provider  2 . 
   A copy right management section  13  transmits the information indicating the result of usage of content of the user home network  5  to the copy-right management organization, for example, JASRAC (Japanese Society for Rights of Authors, Composers and Publishers). 
   A key server  14  stores the distribution key Kd and thereby supplies such key to the content provider  2  via the content provider management section  12  and also supplies the key to the user home network  5  via the user management section  18  or the like. A career data management section  15  stores the accounting information, PT corresponding to the content and UCP corresponding to the content, etc. output from a user management section  18 . 
   A profit distribution section  16  calculates, based on various information pieces supplied from the career data management section  15 , the profits of the EMD service center  1 , content provider  2  and service provider  3  and then outputs the result of calculation to the service provider management section  11 , content provider management section  12 , account section  20  and copy-right management section  13 . 
   A mutual authentication section  17  executes mutual authentication of apparatuses of the content provider  2 , service provider  3  and user home network  5 . The user management section  18  generates a predetermined registration list corresponding to the predetermined process and transmits this list to the user home network  5  together with the distribution key Kd. 
   An accounting demand section  19  calculates the accounting for a user based, for example, on the accounting information, UCP and PT supplied from the career data management section  15  and then supplies the result to the account section  20 . The account section  20  executes payment to user, content provider  2  and service provider  3  and also executes settlement of account for external banks not illustrated through the on-line communication based on the amount of usage accounting to be collected. The account section  20  also notifies the result of settlement of account to the user management section  18 . An audit section  21  inspects the accounting information supplied from the apparatus of user home network  5  and validity of PT and UCP (namely, to check whether illegal usage is conducted or not). 
     FIG. 4  is a block diagram illustrating the functional structure of the content provider  2 . A content server  31  stores the content distributed to users and supplies the content to a water mark adding means  32 . The water mark adding means  32  adds the watermark to the content supplied from the content server  31  and then supplies such content with watermark to a compression means  33 . 
   The compression means  33  compresses the content supplied from the watermark adding means  32  depending on the system such as ATRA C 2  (Adaptive Transform Acoustic Coding  2 )(trade-mark), etc. and then supplies the compressed content to an encryption means  34 . The encryption means  34  ciphers the content compressed in the compression means  33  with the common key encryption system such as DES (Data Encryption Standard) using the random number supplied from the random number generation means  35  as a key (hereinafter, this random number is referred to as content key Kco) and thereafter outputs the result of encryption to a secure container generation means  38 . 
   The random number generation means  35  supplies the random number of predetermined number of bits as the content key Kco to the encryption means  34  and  36 . The encryption means  36  ciphers the content key Kco with the common key encryption system such as DES using the distribution key Kd supplied from the EMD service center  1  and then outputs the result of encryption to the secure container generation means  38 . 
   DES is the encryption system in which 64 bits of plain text is processed as one block using the common key of 56 bits. The DES process is composed of the part for mixing the plain text to convert to the encrypted text (data mixing means) and the part for generating the key (magnifying key) used in the data mixing part from the common key (key processing means). Since all algorithms of DES are disclosed, the basic process in the data mixing means will be explained here. 
   First, the 64 bits of plain text is divided to H 0  of upper 32 bits and L 0  of lower 32 bits. The magnifying key K 1  of 48 bits supplied from the key processing means and L 0 O of the lower 32 bits are input and an output of the F function in which the lower 32 bits are mixed can be calculated. The F function is composed of two kinds of basic conversion including “character replacement” for replacing a numeral depending on the predetermined rule and “relocation” for relocating the bit position depending on the predetermined rule. Next, H 0  of upper 32 bits and output of F function are exclusively ORed and the result is defined as L 1 , while L 0  as H 1 . 
   Based on H 0  of upper 32 bits and L 0  of lower 32 bits, the process explained above is repeated for 16 times and H 16  of upper 32 bits and L 16  of lower 32 bits obtained are output as the encrypted sentence. Encryption may be realized by inversely following the procedures explained above using the common key used for the encryption. 
   A policy memory  37  stores UCP to be set corresponding to the content and outputs this UCP to the secure container generation means  38 .  FIG. 5  illustrates UCPA in such a case that the content A stored in the content server  31  is provided in the single form. 
   As illustrated in  FIG. 5 , UCP includes the predetermined information set to each item of “ID of content provider”, “ID of UCP”, “Period of validity of UCP”, “Usage condition” and “Usage content”. To the “ID of content”, ID of content corresponding to UCP is set. To the “ID of content” of UCP, ID of content A is set. 
   To the “ID of content provider”, ID of content provider of the content providing source is set, while to the “ID of content provider” of UCPA, ID of content provider  2  is set. Moreover, the predetermined ID assigned to each UCP is set to the “ID of UCP” and ID of UCPA is set to the “ID of UCP”. To the “Period of validity of UCP”, the information indicating the period of validity of UCP is set and to the “Period of validity of UCP” of UCP, the period of validity of UCPA is set. 
   The “Usage condition” includes the predetermined information to be set to each item of “User condition” and “Device condition”. To the “User condition”, condition of user who can select this UCP is set. To the “Device condition”, condition of device which can select this UCP is set. 
   In the case of UCPA, “Usage condition  10 ” is set and to the “User condition  10 ” of “Usage condition  10 ”, the information indicating that the predetermined usage point given corresponding to the usage frequency of EMD system is 200 points or more (“200 points or more”) is set. Moreover, to the “Device condition  10 ” of “Usage condition  10 ”, the information indicating that there is no condition (“No condition”) is set. Namely, only the user having the usage point of 2000 points or more can select the UCPA. 
   The “Usage content” includes the information to be set to each item of “ID” and “Format”. To the “ID”, the predetermined ID assigned to the information to be set to the “Usage content”is set. To the “Format”, the information indicating usage format of content is set. 
   In the case of UCPA, the six usage contents from “Usage content  11 ” to “Usage content  16 ” are provided and to the “ID 11 ” of “Usage content  11 ”, the predetermined ID assigned to the “Usage content  11 ” is set. In the “Format  11 ”, the information indicating the usage format for reproducing the content by purchasing it (“purchase and reproduction”) is set. A user can reproduce the content A without any limitation by purchasing the right for use in the usage format of “Purchase and reproduction”. 
   To the “ID  12  ” of “Usage content  12 ”, the predetermined ID assigned to the “Usage content  12 ” is set. To the “Format  12 ”, usage format of “reproduction with limitation of period” and start timing (time) and end timing (time) of such period are set. A user is capable of reproducing the content A only in the predetermined period (time) by purchasing the right for “Reproduction with limitation of period”. 
   To the “ID  13 ” of “Usage content  13 ”, the predetermined ID assigned to the “Usage content  13 ” is set. To the “Format  13 ”, the usage format of “Reproduction with limitation of period” and predetermined specified period are set. A user is capable of reproducing the content A until the reproducing period (total time) expires the predetermined specified period (time) by purchasing the right for “Reproduction with limitation of period”. 
   To the “ID  14 ” of “Usage content  14 ”, the predetermined ID assigned to the “Usage content  14 ” is set. To the “Format  14 ”, usage format and number of times of usage N of “Pay Per Play N” are set. A user is capable of reproducing the content A for N times by purchasing the right for “Pay Per Play N”. 
   To the “ID  15 ” of “Usage content  15 ”, the predetermined ID assigned to the “Usage content  15 ” is set. To the “Format  15 ”, usage format of “Format  12 →Format  11 ” is set. A user is capable of purchasing this right when the user has purchased the right for use in the usage format of  “Reproduction with limitation of period”. A user is also capable of utilizing the content A in the usage format of “Purchase and reproduction” (Format  11 ) by purchasing this right. 
   To the “ID  16 ” of “Usage content  16 ”, the predetermined ID assigned to the “Usage content  16 ” is set. To the “Format  16 ”, the usage format “Format  14 &gt;=11 times” is set. A user is capable of purchasing this right when the user has purchased  10  or more rights of “Pay Per Play N”. 
   Returning to  FIG. 4 , the secure container generation means  38  generates, for example as illustrated in  FIG. 6 , the content provider secure container consisting of content A (encrypted with content key KcoA), content key KcoA (encrypted with the distribution key Kd), UCPA and signature thereof. As the signature, the data to be transmitted (in this case, content A (encrypted with the content key KcoA)), content key KcoA (encrypted with the distribution key Kd) and Hash value obtained by applying the Hash function to the entire part of UCPA are encrypted with the secret key (in this case, the secret key Kscp of content provider  2 ) of the disclosed key encryption. 
   The secure container generation means  38  also adds the certificate of content provider  2  illustrated in  FIG. 7  to the content provider secure container and then transmits it to the service provider  3 . This certificate includes a version number of the certificate, a serial number of the certificate assigned to the content provider  2  from the authentication department, algorithm and parameter used in the signature, name of authentication department, period of validity of certificate, name of content provider  2 , disclosed key Kpcp and signature (encrypted with the secret key Ksca of authentication department) of the content provider  2 . 
   The signature is the data for checking falsification and authenticating a person who has generated the certificate and is generated by taking the Hash value with the Hash function based on the data to be transmitted and then ciphering such Hash value with the secret key of the disclosed key encryption. 
   Collation of Hash function and signature will be explained. The Hash function is used for inputting the predetermined data to be transmitted, compressing the data to the data of the predetermined bit length and then outputting the data as the Hash value. The Hash function has the characteristic that when it is difficult to forecast an input from the Hash value (output) and when one bit of data input to the Hash function is changed, many bits of Hash value are also changed and therefore it is moreover difficult to find out the input data having the identical Hash value. 
   A receiving side having received the signature and data decodes the signature with the disclosed key of the disclosed key encryption and obtains the result (Hash value) of decoding. Moreover, the Hash value of received data is calculated and it is determined whether the calculated Hash value is identical to the Hash value obtained by decoding the signature or not. When the Hash value of the data transmitted is determined to be identical to the decoded Hash value, it is proved that the received data is not falsified and the data has been transmitted from a sending side holding the secret key corresponding to the disclosed key. As the Hash function of signature, MD4, MD5 and SHA-1 are used. 
   Next, the disclosed key encryption will be explained. For the common key encryption system in which the identical key (common key) is used for encryption and decoding, the key used for encryption is different from the key used for decoding in the disclosed key encryption system. In the case of using the disclosed key encryption, if one key is disclosed, the other key may be kept secret. The key which may be disclosed is called a public key and the other key which should be kept secret is called a secret key. 
   The typical RSA (Rivest-Schamir-Adleman) encryption in the disclosed key encryption will be explained briefly. First, two sufficiently large prime numbers p and q are obtained and then n which is a product of p and q is obtained. Here, the least common multiple L of (p−1) (1-1) is calculated and moreover the number e which is larger than 3 but under L and is in the relationship of the prime number for L is obtained (namely, e and L are divided in common with only 1). 
   Next, the inverse element d of multiplication of e regarding the multiplication in which L is defined as modulus is obtained. Namely, relationship ed=1 mod L is formed among e and L and d can be calculated with the Euclidean mutual division. In this case, n and e are defined as the public keys and p, q and d are defined as the secret keys. 
   The encrypted sentence C can be calculated by the process of equation (1) from the plain-text M.
 
C=M^e mod n  (1)
 
   The encrypted sentence C is decoded to the plain text with the process of equation (2).
 
M=C^d mod n  (2)
 
   Although proofing is omitted here, conversion of plain text to the encrypted sentence with the RSA encryption and decoding thereof are based on the Fermat&#39;s little theorem and the equation (3) can be established.
 
M=C^d=(M^e)^d=M ^(ed)=M mod n  (3)
 
   When the secret keys p and q are known, the secret key d can be calculated from the public key e, but if the number of digits of the public key n is increased in such a degree that factorization in prime factors of the public key n is difficult from the viewpoint of calculation, the secret key d cannot be calculated from the public key e and decoding is impossible only by detecting the public key n. As explained above, in the RAS encryption, different keys may be used for the encryption and decoding, respectively. 
   Moreover, the elliptical curve encryption which is another example of public key encryption will also be explained briefly. A certain point on the elliptical curve y^2=x^3+ax+b is defined as B. Addition of the points on the elliptical curve are defined and nB indicates the result of addition of B of n times. Similarly, subtraction is also defined. It is proved that subtraction of n from B and nB is difficult. Here, B and nB are defined as the public keys and n as the secret key. Using a random number r, the encrypted sentences C 1  and C 2  can be calculated from the plain text with the processes of the equations (4) and (5) using the public key.
 
 C 1= M+rnB   (4)
 
C2=rB  (5)
 
   The encrypted sentences C 1  and C 2  can be decoded to the plain text with the process of equation (6).
 
 M=C 1− nC 2  (6)
 
   The sentence having the secret key n can be decoded. As explained above, as in the case of the RSA encryption, different keys may be used respectively for the encryption and decoding in the elliptical curve encryption system. 
   Returning again to  FIG. 4 , the mutual authentication means  39  of content provider  2  mutually authenticates the EMD service center  1  prior to receiving the supply of the distribution key Kd from the EMD service center  1 . The mutual authentication means  39  can also authenticate the service provider  3  prior to transmission of the content provider secure container to the service provider  3 . In the case of this example, since the content provider secure container does not include the information which shall particularly be kept secret, this mutual authentication is not always required. 
   Next, with reference to the block diagram of  FIG. 8 , the functional structure of the service provider  3  will be explained. The content server  41  stores the content (encrypted with content key Kco), content key Kco (encrypted with the distribution key Kd), UCP and signature of content provider  2  included in the content provider secure container supplied from the content provider  2  and then supplies these data to the secure container generation means  44 . 
   A value adding means  42  verifies validity of content provider secure container based on the signature included in the content provider secure container supplied from the content provider  2  and when it verifies validity, it generates PT corresponding to UCP included in the content provider secure container and supplies this PT to the secure container generation means  44 .  FIGS. 9A and 9B  illustrate PAT-1 ( FIG. 9A ) and PAT-2 ( FIG. 9B ) generated corresponding to UCPA of  FIG. 5 . PT includes the predetermined information pieces to be set to each item of “ID of content provider”, “ID of UCP”, “Period of validity of UCP”, “ID of service provider”, “ID of PT”, “Period of validity of PT”, “Price condition” and “Price content”. 
   To each item of “ID of content”, “ID of content provider”, “ID of UCP” and “Period of validity of UCP” of PT, the information pieces of the corresponding items are set respectively. Namely, to the “ID of content” of PAT-1 and PAT-2 , ID of content is set, while to the “ID of content provider”, ID of content provider  2  is set, to the “ID of UCP”, ID of UCPA is set and to the “Period of validity of UCP”, the period of validity of UCPA is set, respectively. 
   To the “ID of service provider”, ID of service provider as the providing source of PT is set. To the “ID of service provider” of PAT-1 and PAT-2 , ID of service provider  3  is set respectively. To the “ID of PT”, the predetermined I D assigned to each PT is set and to the “ID of PT” of PAT-1 , ID of PAT-1 is set and to the “ID of PT”, ID of PAT-2 are set respectively. To the “Period of validity of PT”, the information indicating the period of validity of PT is set, to the “Period of validity of PT” of PAT-1 , the information indicating the period of validity of PAT-1 is set and to the “Period of validity of PT” of PAT-2 , the information indicating the period of validity of PAT-2 is set. 
   Like the “Usage condition” of UCP, the “Price condition ” is formed of the items of “User condition” and “Device condition”. To the “User condition”, the information indicating the condition of user who can select this PT is set and to the “Device condition”, the information indicating condition of device which can select this PT is set. 
   In the case of PAT-1 , the “Price condition  10 ” is set and to the “User condition  10 ” of the “Price condition  10 ”, the information indicating that a user is a male (“Male”) is set and to the “Device condition  10 ”, the “No-condition” is set. Namely, only a male user can select PAT-1 . 
   In the case of PAT-2 , the “Price condition  20 ” is set and to the “User condition  20 ” of the “Price condition  20 ”, the information indicating that a user is a female (“Female”) is set. To the “Device condition  20 ” thereof, the “No-condition” is set. Namely, only a female can select PAT-2 . 
   A usage accounting of usage format being set to “Format” of “Usage content” of the corresponding UCP (price of right for using content in the usage format) is indicated in the “Price content” of PT. The ¥2000 of the “Price content  11 ” of PAT-1 and ¥1000 of “Price content  21 ” of PAT-2 are charges for using the content A in the usage format of “Purchase and Reproduction” (price of the right for using in the usage format of “Purchase and Reproduction”). 
   The ¥600 of “Price content  12 ” of PAT-1 and ¥300 of “Price content  22 ” of PAT-2 indicate the prices of right for using the content A in the usage format of “Reproduction with period limitation” from the “Format  12 ” of “Usage content  12 ” of UCPA. The ¥300 of “Price content  13 ” of PAT-1 and the ¥150 of “Price content  23 ” of PAT-2 indicate the prices of right for using the content A in the usage format of “Reproduction with usage period limitation”. The ¥100 of “Price content  14 ” of PAT-1 and the ¥50 of “Price content  24 ” of PAT-2 indicate the prices of right for using the content A in the usage format of “Pay Per PlayN(=1)” from the “Format  14 ” of “Usage content  14 ” of UCPA. 
   The ¥1950 of “Price content  15 ” of PAT-1 and the ¥980 of “Price content  25 ” of PAT-2 indicate the prices of right of “Purchase and Reproduction” when having the right of “Reproduction with period limitation” from the “Format  15 ” of “Usage content  15 ” of UCPA. The ¥50 of “Price content  16 ” of PAT-1 and the ¥25 of “Price content  26 ” of PAT-2 indicate the prices of right of the 11th “Pay Per PlayN(=1)”. 
   Returning to  FIG. 8 , the policy memory means  43  stores UCP of content supplied from the content provider  2  and supplies it to the secure container generation means  44 . The secure container generation means  44  generates, as illustrated for example in  FIG. 10 , the service provider secure container consisting of the content A (encrypted with the content key KcoA), content key KcoA (encrypted with the distribution key Kd), UCPA, signature of content provider  2 , PAT-1 , A-1 and signature of service provider  3  thereof. 
   The secure container generation means  44  also supplies the generated service provider secure container to the user home network  5  with addition, as illustrated in  FIG. 11 , of the version number of certificate, serial number of certificate assigned to the service provider  3  by the authentication bureau, algorithm and parameter used for signature, name of authentication bureau, period of validity of certificate, name of service provider  3 , public key kpsp of service provider  3  and signature. 
   Returning again to  FIG. 8 , the mutual authentication means  45  mutually authenticates the user home network  5  prior to transmission of service provider secure container to the user hole network  5  but the mutual authentication is not executed, for example, when the network  4  is a satellite communication. In the case of this example, since the secret information is not particularly included in the content provider secure container and service provider secure container, the service provider  3  is not required to execute the mutual authentication of content provider  2  and user home network  5 . 
   Next, an example of structure of the receiver  50  forming the user home network  5  is explained with reference to the block diagram of  FIG. 12 . SAM (Secure Application Module)  51  generates UCS and accounting information based on UCP and PT included in the service provider secure container supplied from the service provider  3  and stores these data with the content key Kco included in the service provider secure container (encrypted with the distribution key Kd).  FIG. 13  illustrates the UCSA generated on the basis of UCPA of  FIG. 5  and price content  11  of PAT-1 of  FIG. 9A . UCS includes , as illustrated in  FIG. 13 , the information set to each item of the “ID of, “ID of content provider”, “ID of UCP”, “Period of validity of UCP”, “ID of service provider”, “ID of PT”, “Period of validity of PT”, “ID of UCS”, “ID of SAM”, “ID of User”, “Usage content”, “Parameter” and “Purchase history”. 
   To each item of “ID of content”, “ID of content provider”, “ID of UCP”, “Period of validity of UCP”, “ID of service provider”, “ID of PT” and “Period of validity of PT” of UCS, the information of corresponding items is set. Namely, to the “ID of content” of UCSA of  FIG. 13 , ID of the content A is set, to the “ID of content provider”, ID of the content provider  2 , to the “ID of UCP”, ID of UCPA, to the “Period of validity of UCP”, the period of validity of UCPA, to the “ID of service provider”, ID of service provider  3 , to the “ID of PT”, ID of PTA-a, and to the “Period of validity of PT”, period of validity of PAT-1 , respectively. 
   To the “ID of UCS”, the predetermined ID assigned to UCS is set, to the “ID of UCS” of UCSA, ID of UCSA is set. To the “ID of SAM”, ID of SAM of device is set. To the “ID of SAM”, ID of SAM  51  of the receiver  50  is set. To the “ID of user”, ID of user using the content is set and to the “ID of user” of UCSA, ID of user of the receiver  50  is set. 
   The “Usage content” is formed of the items of “ID” and “Format”. To these items, the information of the corresponding items of the predetermined “Usage content” of UCP is set. To the “Parameter”, the information corresponding to the usage format set to the “Format” of “Usage content” is set. For instance, when the “Reproduction with usage period limitation” being set to the “Format  13 ” of “Usage content  13 ” of UCPA is set to the “Format” of “Usage content” of UCSA, the total time of reproduction is set to the “Parameter”. Moreover, when “Pay Per PlayN” of “Usage content  14 ” of UCPA is set, the remaining number of times of reproduction is set to the “Parameter”. As the “Purchase history”, the purchase history of right for the content for which the ID is set to the “IC of content” of UCS is set. 
   To the “Usage content” of UCSA, any one information among “Usage content  11 ” to “Usage content  16 ” of UCPA is set. 
     FIG. 14  illustrates the accounting information A generated simultaneously with UCSA of  FIG. 13 . The accounting information includes, as illustrated in  FIG. 14 , the predetermined information to be set to each item of the “ID of content”, “ID of content provider”, “ID of UCP”, “Period of validity of UCP”, “ID of service provider”, “ID of PT”, “Period of validity of PT”, “ID of UCS”, “ID of SAM”, “ID of user”, “Usage content” and “Accounting amount”. 
   To the “ID of content”, “ID of content provider”, “ID of UCP”, “Period of validity of UCP”, “ID of service provider”, “ID of PT”, “Period of validity of PT”, “ID of UCS”, “ID of SAM”, “ID of user”, “Usage content” of accounting information, information of corresponding items is set respectively. Namely, to the “ID of content” of the accounting information A of  FIG. 14 , ID of the content A is set. To the “ID of content provider”, ID of the content provider  2  is set. To the “ID of UCP”, ID of UCPA is set. To the “Period of validity of UCP”, the period of validity of UCPA is set. To the “ID of service provider”, ID of the service provider is set. To the “ID of PT”, ID of PAT-1 is set. To the “Period of validity of PT”, the period of validity of PAT-1 is set. To the “ID of UCS”, ID of UCSA is set. To the “ID of SAM”, ID of SAM 5  is set. To the “ID of user”, ID of user of the receiver  50  is set. To the “Usage content”, content of “Usage content” of UCSA is set. To the “Accounting amount”, the amount of accounting is set when accounting is accounted with the price other than the price indicated in the “Price content” provide for PT. 
   SAM  51  also decodes the content stored in the external memory  52  (encrypted with the content key Kco) on the basis of generated UCS and then outputs the content to the reproducing means  53 . 
   The external memory  52  stores the content (encrypted with the content key Kco) and also supplies, as requested, the content (encrypted with the content key Kco) to SAM 51 . The reproducing means  53  is formed, for example, of D/A converter or the like to convert the content (decoded) supplied from SAM 51  to the analog signal to output from external device (for example, speaker). 
   Next, with reference to  FIG. 15 , an example of functional structure of SAM  51  of the receiver  50  will be explained. The memory means  62  stores UCP and PT included in the service provider secure container and generated UCS. The control means  61  controls each means and is also operated by a user in its manipulation means not illustrated. When the signal to instruct reproduction and purchase of content is input from the manipulation means, UCP, PT and UCS stored in the memory means  62  are output to the content key output means  63  or accounting information generation means  66 . 
   A content key output means  63  holds the content key Kco (encrypted with the distribution key Kd) and determines, when the content is reproduced, whether reproduction of content is possible or not depending on the UCP, PT and UCS supplied from the control means  61 . When reproduction is possible, the content key Kco (encrypted with the distribution key Kd) is output to a decoding means  64 . The content key output means  63  also updates UCS depending on the usage format of content each time when the content is reproduced. 
   The decoding means  64  decodes the content key Kco (encrypted with the distribution key Kd) supplied from the content key output means  63  with the distribution key Kd separately supplied from the EMD service center  1  and also decodes the content (encrypted with the content key Kco) read via an interface  65  to output it to the reproducing means  53 . 
   An accounting information generation means  66  generates, when the content is purchased (when the right for using the content is purchased), the accounting information depending on the right to be purchased and also generates or updates UCS. The accounting information generated with the accounting information generation means  66  is transmitted via a communication means  67  to the EMD service center  1  and is then processed. The communication means  67  makes communication with the service provider  3  or EMD service center  1  via the network  4  to receive or transmit the predetermined information. 
   Next, the processing procedures of receiver  50  in such a case of purchasing the right for using the content A will be explained with reference to the flowchart of  FIG. 16 . In the case of this example, it is assumed that the service provider secure container of  FIG. 10  is supplied to the receiver  50  from the service provider  3 . 
   When the a user manipulates the operation means not illustrated of the receiver  50  and a signal (including the ID of content A) instructing purchase of the content A is input to the control means  51  of SAM 51  in the step S 101 , the control means  61  determines, in the step S 102 , whether UCS setting the ID of content A to the “ID of content” is stored in the memory means  62  or not. When UCS is not stored in the memory means  62 , the process goes to the step S 103 . For instance, when the right for using the content A is purchased for the first time, UCSA setting the ID of content A to the “ID of content” as illustrated in  FIG. 13  is not stored (generated) in the memory means  62  and therefore the process goes to the step S 103 . 
   In the step S 103 , UCP and PAT-1 , PAT-2 included in the service provider secure container of  FIG. 10  are extracted and are then displayed on the display means (not illustrated) of the receiver  50 . A user executes, at the operation means of receiver  50 , the manipulation for selecting the “Usage content” setting the predetermined usage format to the “Format” from UCPA by referring to the display. 
   In the step S 104 , the control means  61  outputs the “Usage content” of UCPA selected by user in the step S 103 , UCPA, PAT-1 , and PAT-2 to the accounting information generation means  66 . In the step S 105 , the accounting information generation means  66  determines whether the “Usage content” of UCPA selected by user in the step S 103  is adequate or not. When it is determined as the adequate “Usage format”, the process goes to the step S 106 . In this case, since UCSA does not exist, namely the right for using the content A is purchased for the first time, if the “Usage format  15 ” or “Usage format  16 ” which may be used to purchase again the right is selected in the step S 103 , it is determined as the non-adequate “Usage format”. Meanwhile, when the “Usage content  11 ” to “Usage content  14 ” of UCPA is selected in the step S 103 , it is determined as the adequate “Usage content”. 
   In the step S 106 , the accounting information generation means  66  generates UCS (UCSA, in this case) and the accounting information (accounting information A in this case) based on the “Usage content” of UCPA selected in the step S 103  and the “Price content” of the corresponding PT (PAT-1 , in this case) and then outputs such data to the control means  61 . 
   In the step S 107 , the control means  61  makes the memory means  62  store the UCSA and accounting information A supplied from the accounting information generation means  66 . As explained above, when the right for using the content is purchased, the process is completed. 
   When it is determined in the step S 102  that UCS including ID of the content for purchasing the right is stored in the memory means  62 , the control means  61  of SAM  51  reads such UCS from the memory means  62  in the step S 108 . For example, when the right for using the content A is purchased and the right is purchased again under the condition that UCSA is stored in the memory means  62  with the processes from the steps S 101  to S 107  explained above, the process goes to the step S 108  to read UCSA from the memory means  62 . 
   Next, in the step S 109 , UCSA read in the step S 108  and UCPA, PAT-1 , PAT-2 stored in the memory means  52  in this case are displayed on the display means of receiver  50 . Here, the user executes the manipulation for selecting the “Usage content” setting the desired usage format to the “Format” from UCPA at the operation means of receiver  50  by referring to such display. 
   In the step S 110 , the control means  61  outputs the “Usage content” of UCPA selected by the user in the step S 109  and UCSA, UCPA and PAT-1, PAT-2 stored in the memory means  62  to the accounting information generation mans  66 . 
   In the step S 111 , the accounting information generation means  66  determines whether the “Usage content” of UCPA selected by user in the step S 109  is adequate (corresponding to UCSA) or not. For example, when the “Reproduction with period limitation” (format  12 ) is set to the “Format” of the “Usage content” of UCSA, namely when the “Usage content  12 ” of UCPA is selected and the content A is used for “Reproduction with period limitation”, if the “Usage content  15 ” setting the “Format  12 →Format  11 ” in the “Format” is selected, it is determined as the adequate “Usage content”. On the other hand, when “Pay Per PlayN”, for example, is set to the “Format” of the “Usage content” of UCSA is set, namely when the content A is used by the “Pay Per PlayN”, if the “Usage content  15 ” is selected, it is determined as non-adequate “Usage content”. 
   If the “Usage content  16 ” setting the “Format  14 &gt;=11th times” to the “Format” when the purchase history of 10 times or more for the right of “Pay Per PlayN” is stored in the “Purchase history” of UCSA, it is determined as the adequate “Usage content”. Meanwhile, if the “Usage content  16 ” is selected when only the purchase history under 11th times is stored to the “Purchase history” of UCSA, it is determined as non-adequate “Usage content”. 
   In the step S 111 , when the “Usage content” of UCPA selected in the step S 109  is determined as adequate “Usage content”, the process goes to the step S 112  and the accounting information generation means  66  generates the accounting information A and updates UCSA to output to the control means  61 , based on the “Usage content” of UCPA selected in the step S 109  and the “Price content” of corresponding PTA. With update of UCSA, in this case, the purchased right content is added to the “Purchase history” of UCSA. In the step S 113 , the control means  61  stores such content of right to the memory means  62 . Thereafter, the process is completed. 
   As explained above, the right for using the content is purchased (purchased again), but, in this case, the accounting is settled on the basis of the accounting information generated in this case (in the step S 106  or S 112 ). 
   In above explanation, since the content of right to be purchased again is set to UCP (for example, the “Usage content  15 ” and “Usage content  16 ” of UCPA) and the price content of the corresponding PT (for example, “Price content  15 ” and “Price content  16 ” of PAT-1 ) is provided, accounting for purchase of the content is read as the amount of price content of the corresponding PT, for example, with the ID of UCP, ID of usage content of UCP or ID of PT, included in the generated accounting information (step S 106  or step S 112 ) and is accounted. 
   However, it is also assumed that the usage content corresponding to the right purchased again is set to UCP and moreover its price content is not set to PT. In this case, the predetermined price is set to the “Accounting amount” of the accounting information and the accounting is accounted depending on such amount. For example, when the right for “Purchase and Reproduction” is purchased under the condition of having the right for “Reproduction with period limitation” if the “Usage content  15 ” is not provided in UCPA, the price of “Reproduction with period limitation” (¥600 of the “Price content  12 ” of PAT-1 is subtracted from the price of “Purchase and Reproduction” (¥2000 of the“Price content  11 ” of PAT-1 ) and the result of subtraction (¥1400 (=2000−600) is set to the “Accounting amount” of the accounting information. Namely, in this case the accounting of ¥1400 is accounted. 
   Moreover, in above explanation, the right for using the content of single form is purchased, but this explanation can also be adapted to the example where the right for using the content of album form (a plurality of contents) is purchased. In this case, the processing procedures of receiver  50  will be explained by referring a gain the flowchart of  FIG. 16 . In the case of this example, the service provider secure container including a plurality of contents (in this case, four contents from  1  to  4 ) illustrated in  FIG. 17 , corresponding content key Kco (in this case, four content keys  1  to  4 ) and UCSZ and PTZ in which ID of a plurality of contents (in this case, respective ID of four contents  1  to  4 ) is set to the “ID of content” is supplied to the receiver  51  from the service provider  3 . Moreover, in this case, the right for using the content  1  and content  2  in the “Purchase and Reproduction” mode are assumed to be held (purchased), namely UCS 1  of  FIG. 20  (UCS where ID of content  1  is set) and UCS 2  of  FIG. 21  (UCS where ID of content  2  is set), content key Kco 1 ,  2  and contents  1 ,  2  are assumed to be held in the receiver  50 . 
   When the operation means of receiver  50  is manipulated by a user and the signal (respectively including the ID of the contents  1 ,  2 ,  3 ,  4 ) instructing the purchase of content of the album form is input to the control means  61 , the control means  61  determines, in the step S 102 , that UCS corresponding to the purchase of this time exists because UCS 1  setting the ID of content  1  and UCS 2  including the ID of content  2  are stored in the memory means  62  and the process goes to the step S 108  to read UCS 1 ,  2  from the memory means  62 . 
   Next, in the step S 109 , UCS 1 ,  2  read in the step S 108  and UCPA and PTX, extracted in this case from the service provider secure container are displayed on the display means of receiver  50 . In response to this display, the user executes the manipulation for selecting the “Usage content  101 ” of UCPZ to the operation mans of receiver  50 . 
   In the step S 110 , the control means  61  outputs the content of the “Usage content  101 ” of UCPZ selected by user in the step S 109 , UCS 1 ,  2 , UCPZ and PTZ to the accounting information generation mans  66 . 
   Next, in the step S 111 , the accounting information generation mans  55  determines whether the “Usage content  101 ” of UCPZ selected by user in the step S 109  is adequate or not. In this case, the “Usage content  101 ” of UCPZ is determined as the adequate “Usage content” and the process goes to the step S 112 . 
   In the step S 112 , the accounting information generation means  66  generates the accounting information to update UCS 1 ,  2  based on the “Usage content  101 ” of UCPZ selected in the step S 109  and the “Price content  101 ” of the corresponding PTZ. In this case, to the “accounting amount” of the accounting information, the amount (¥1000 (=2500−1500)) obtained by subtracting the amount (for example, ¥1500) paid for purchase of right for “Purchase and Reproduction” of the content  1  and content  2  from the ¥2500 of the “Price content  101 ” of PTZ is set. 
   In the step S 112 , the accounting information generation means  66  outputs the accounting information generated in the step S 112  and updated UCS  1 ,  2  to the control means  61 . In the step S 113 , the control means  61  causes the memory means  52  to store such accounting information and UCS 1 ,  2 . In the timing to execute the process in the step S 113 , contents  2 ,  3 ,  4 , content keys Kco 2 ,  3 ,  4 , UCPZ and PTZ included in the service provider secure container are stored in the external memory  52 . 
   As explained above, the right for using the content of album form may be purchased. 
   Next, the processing procedures of receiver  50  for using the content A based on the usage format corresponding to the right purchased will be explained with reference to the flowchart of  FIG. 22 . In the case of this example, it is assumed that UCSA, UCPA and PAT-1 , PAT-2 are already stored in the memory means  62 , while the content A is already stored in the external memory  52 . 
   In the step S 201 , when the operation means not illustrated of the receiver  50  is manipulated by user and the reproduced signal of content A is input to the control means  61  from the operation means, the control means  61  reads UCSA from the memory means  62  in the step S 202  and then outputs UCSA to the content key output means  63 . 
   In the step S 203 , the content key output means  63  determines whether the “Purchase and Reproduction” is set or not to the “Format” of the “Usage content” of UCSA supplied from the control means  61 . When the “Purchase and Reproduction” is set, the process goes to the step S 204 . 
   In the step S 204 , the content key output means  63  outputs the content key KcoA (encrypted with the distribution key Kd) to the decoding means  64 . Thereby, the reproducing operation of content A (encrypted with the content key Kco) is started in the step S 205 . In more practical, the decoding means  64  decodes the supplied content key Kco (encrypted with the distribution key Kd) with the distribution key Kd supplied separately from the EMD service center  1  and outputs the decoded content to the reproducing means  53 . The reproducing means  53  converts the content (decoded content) supplied from the decoding means  64  of SAM  51  and then outputs the content of analog signal from a speaker, for example, not illustrated. 
   When the “Purchase and Reproduction” is not set to the “Format” of the “Usage content” of UCSA in the step S 203 , the process goes to the step S 206  and the content key output means  63  determines whether the “Reproduction with period limitation” is set or not. When it is set, the process goes to the step S 207 . 
   The content key output means  63  obtains the respective periods (times) in the step S 207  by referring to the “Format” of the “Usage content” of UCSA where the start period (time) and end period (time) are set. Next, the content key output means  62  detects, in the step S 208 , the current time by referring the built-in clock and determines whether the current time is within the range of the obtained period (time) or not. When the current time is within the range obtained, the process goes to the step S 204  and the subsequent processes are then executed. Namely, the content A is reproduced. 
   When it is determined, in the step S 209 , that the current time is not within the range of the time obtained in the step S 207 , the process is completed. Namely, the content A is not reproduced. 
   When the “reproduction with period limitation” is not set to the “Format” of the “Usage content” of UCSA in the step S 206 , the process goes to the step S 210  and it is then determined whether the “Reproduction with usage period limitation” is set or not. When it is set, the process goes to the step S 211 . The content key output means  63  obtains in the step S 211  the reproduction time by referring to the “Parameter” of UCSA and it is then determined in the step S 212  whether such reproduction time is exceeding or not the specified time set to the “Format”. When it is determined that such reproduction time does not exceed the specified time, namely when the reproduction is possible, the process goes to the step S 213 . When it is determined in the step S 212  that the reproducing time has exceeded the specified time, the process is completed. Namely, the content A is never reproduced. 
   In the step S 213 , the content key output means  63  outputs the content key KcoA (encrypted with the distribution key Kd) to the decoding means  64 . Thereby, the reproducing operation of content A is started in the step S 214  as in the case of the step S 205 . 
   Next, the content key output means  63  starts, in the step S 215 , the measurement of reproducing time of the content A with the built-in clock and determines, in the step S 216 , whether the total time of the result of measurement and the reproducing time before the current use obtained in the step S 211  has exceeded the specified time or not. When the total time is determined not exceeding the specified time, the process goes to the step S 217 . 
   The content key output means  63  determines, in the step S 217 , whether a user manipulates the operation means of the receiver  50  and the instruction for stopping reproduction of the content A is issued or not. When it is determined that the instruction for stopping reproduction is not issued, the process returns to the step S 216 . 
   When it is determined that the instruction for stopping reproduction is issued in the step S 217 , the content key output means  63  stops, in the step S 218 , the measurement of reproducing time started in the step S 215 , sets the total time of the measurement result and the reproducing time obtained in the step S 211  to the “Parameter” of UCSA, then updates UCSA and thereafter outputs UCSA to the control means  61 . In the step S 219 , the control means  61  stores UCSA updated with the content key output means  63  to the memory means  62 . Thereafter, the process is completed. 
   When it is determined that the reproducing time has exceeded the specified time in the step S 216 , the process goes to the step S 218  and the content key output means  63  sets the total time (time exceeding the specified time) of the result measured with the clock and the reproducing time before the current use to the “Parameter” to update UCSA. Next, in the step S 219 , the control means  61  stores UCSA updated with the content key output means  63  to the memory means  62 . Thereafter, the process is completed. 
   When the it is determined in the step S 210  that the “Reproduction with period limitation” is not set to the “Format” of the “Usage content” of UCSA, the process goes to the step S 220 . In this case, since the “Pay Per PlayN” is set there, the number of times of the possible reproduction is read by referring to the “Parameter” and it is then determined in the step S 221  whether the number of times of possible reproduction is set to 0 or not. When it is determined the number of times of possible reproduction is never set to 0, the process goes to the step S 222 . 
   Next, in the step S 222 , the content key output means  63  outputs the content key KcoA (encrypted with the distribution key Kd) to the decoding means  64 . Thereby, in the step S 223 , the reproducing operation of the content A is started as in the case of the step S 205  or step S 214 . 
   In the step S 224 , the content key output means  63  executes once the decrement for the number of times of possible reproduction being set to the “Parameter” of UCSA to update UCSA and then outputs the updated UCSA to the control means  61 . The control means  61  stores, in the step S 225 , the updated UCSA to the memory  62 . 
   As explained above, the content A can be used in the usage format corresponding to the right purchased. 
     FIG. 23  illustrates the other UCSA  10  generated by the accounting information generation means  66  of SAM  51 . In the UCSA  10 , the “Usage history” is further provided in UCSA of  FIG. 13 . In this “Usage history”, the usage result (history) such as the number of times of actual usage of the content A is stored. For instance, when the right for “Purchase and Reproduction” of the content A is purchased and the content A is reproduced for M times, the history of reproduction of M times is stored in the “Usage history”. 
   Next, the purchase process using the “Usage history” of UCSA 10  will then be explained. In the case of this example, history indicating the content A is reproduced for 10 times or more is stored in the “Usage history” of UCSA 10  and UCSA 10  is assumed to be stored in the memory means  62 . Moreover, in this example, it is also assumed that UCPA  10  is included, in place of UCPA of  FIG. 5 , to the service provider secure container supplied to the receiver  50  and PTA10-1, PTA10-2 of  FIG. 9  are also included thereto in place of PAT-1 , PAT-2. 
   The “Usage content  17 ” of UCPA of  FIG. 5  is moreover provided in the UCPA 10  of  FIG. 24 . In the “Usage content  17 ”, the predetermined ID assigned to the “Usage content  17 ” is set to the “ID 17 ”. To the “Format  17 ”, the usage format of “Number of times of reproduction of 10 times→ Format  14 ” is set. When the user has executed reproduction of content A for 10 times or more, it is possible to purchase this right. The user can utilize the content A with “Pay Per PlayN” by purchasing this right. 
   In the PTA10-1 of  FIG. 25A , the “Price content  17 ” is further provided in the PTA-1 of  FIG. 9A . In the PTA10-2 of  FIG. 25B , the “Price content  27 ” of PAT-2 of  FIG. 9B  is moreover provided. The ¥75 of the “Price content  17 ” of PTA10-1 and the ¥45 of the “Price content  27 ” of PTA10-2 indicate the prices of the right for “Pay Per PlayN” when the content A is reproduced for 10 times or more. 
   Next, the purchase process using the “Usage history” of UCSA 10  will then be explained with reference to the flowchart of  FIG. 16 . In the step S 101 , when the purchase instruction is input, it is determined in the step S 102  whether UCS is stored in the memory means  62  or not. In the case of this example, since UCSA 10  is stored in the memory means  62 , the process goes to the step S 108 . The processes of the steps  108  to S 110  are similar to those explained above and the same explanation is omitted here. 
   In the step S 111 , it is determined whether the “Usage content” of UCPA10 selected by the user in the step S 109  is adequate or not. In the case of this example, it is assumed that the “Usage content  17 ” is selected in the step S 109 . In this case, since the history indicating that the content A is reproduced for 10 times or more is stored in the “Usage history” of UCSA10, the “Usage content” selected in the step S 109  is determined as the adequate one and the process goes to the step S 112 . 
   In the step S 112 , the accounting information generation means  66  generates the accounting information on the basis of the “Usage content  17 ” of UCPA10 selected in the step S 109  and the “Price content  17 ” of corresponding PTA10-1 or the “Price content  27 ” of PTA10-2. Namely, in this case, the ¥75 or ¥45 is accounted and the right for “Pay Per CopyN” can be purchased in the price which is rather lower than the price of the “Usage content  14 ” which may be purchased when the content A is not reproduced for 10 times or more. 
   As explained above, the purchase process is executed depending on the usage history. For instance, the price for purchase and reproduction of the content A is set to ¥0, namely the content A is rent at no usage accounting and the price is determined depending on the number of times of reproduction by user. 
   Here, the content is defined as a music data in above explanation but it is not limited to the music data and it may be selected from moving picture data, static picture data, document data or program data. 
   In this case, the system suitable for the kind of content, for example, MPEG (Moving Picture Experts Group) is used for the moving picture for the compression of signal. As the watermark, the watermark of the format suitable for the kinds of content is used. 
   In above explanation, the content, content key Kco, UCS are stored together in the external memory  52  but it is also possible to individually store these data by providing a plurality of memories. 
   In this specification, a system represents the apparatus as a whole, which is formed of a plurality of apparatuses. 
   Moreover, as a distribution medium for providing the computer program which executes the processes explained above, it is also possible to use the communication medium such as network and satellite in addition to a recording medium such as magnetic disc, CD-ROM and solid-state memory or the like.