(19)
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`Europaisches Patentamt
`
`European Patent Office
`
`Office europeen des brevets
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`
`(11)
`
`EP 1100 035 A1
`
`EUROPEAN PATENT APPLICATION
`published in accordance with Art. 158(3) EPC
`
`(43) Date of publication:
`16.05.2001 Bulletin 2001/20
`
`(21) Application number: 00915429.5
`
`(22) Date of filing: 07.04.2000
`
`(84) Designated Contracting States:
`DE FR GB
`
`(30) Priority: 09.04.1999 JP 10333899
`
`(71) Applicant: Sony Corporation
`Tokyo 141-0001 (JP)
`
`(72) Inventors:
`• ISHIBASHI, Yoshihito
`Shinagawa-ku, Tokyo 141-0001 (JP)
`
`(51) Int. Cl.7: G06F 17/60
`
`(86) International application number:
`PCT/JP00/02288
`
`(87) International publication number:
`WO 00/62215 (19.10.2000 Gazette 2000/42)
`
`• MATSUYAMA, Shinako
`Shinagawa-ku, Tokyo 141-0001 (JP)
`• OHISHI, Tateo
`Shinagawa-ku, Tokyo 141-0001 (JP)
`• MUTO, Akihiro
`Shinagawa-ku, Tokyo 141-0001 (JP)
`
`(7 4) Representative:
`Pilch, Adam John Michael et al
`D. YOUNG & CO.,
`21 New Fetter Lane
`London EC4A 1 DA (GB)
`
`(54)
`
`INFORMATION PROCESSING DEVICE AND METHOD, AND PROVIDING MEDIUM
`
`A user who is purchasing the same content
`(57)
`again can buy it at a discount price. "Accounting His(cid:173)
`tory" of accounting information B prepared when the
`content is repurchased is set to 'Discount Price.' Since
`accounts are settled based on the accounting informa(cid:173)
`tion with "Accounting History" set to 'Discount Price,' the
`user who is purchasing the same content again can buy
`it at a discount price.
`
`ID
`
`ID
`CONTENT
`CONTENT PROVIDER
`UCP
`ID
`UCP VALIDITY PERIOD
`SERVICE PROVIDER ID
`PT
`ID
`PT VALIDITY PERIOD
`UCS
`ID
`SAM
`ID
`USER
`ID
`ID
`<=
`(/) > C)
`TYPE
`m
`PARAMETER
`Cl
`.....
`m
`:'.'. CONTROL TRANSFER
`STATUS
`r-
`VJ
`ACCOUNT I NG
`
`ID OF CONTENT A
`ID OF CONTENT PROVIDER 2
`ID OF ucPA
`VALIDITY PERIOD OF UcPA
`ID OF SERVICE PROVIDER 3
`ID OF PTA-1
`VALIDITY PERIOD OF PTA-1
`ID OF ucsA
`ID OF SAM62
`ID OF USER F
`ID OF USAGE DETAILS 15
`TYPE 13-+ TYPE 11
`xx x
`SOURCE: ID OF SAM62
`DESTINATION: ID OF SAM62
`INFORMATION B
`
`FlG.45
`
`Printed by Xerox (UK) Business Services
`2. 16.7 (HRS)/3.6
`
`,...
`<(
`i.n
`("')
`0
`0
`0 ,...
`,...
`c.
`w
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`EP 1 100 035 A1
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`which identifies the first usage details describing the
`purchased rights and the pricing details corresponding
`to the first usage details; a storage step of storing the
`encrypted information, the first usage control status, the
`usage control policy that contains the second use type
`that describes the rights that can be purchased again
`based on the details of the purchased rights, the price
`tags that contain the pricing details corresponding to the
`second usage details, and the key needed to decrypt
`the encrypted information; a second preparation step of
`preparing the second usage control status which identi(cid:173)
`fies the second usage details and the pricing details
`corresponding to the second usage details, based on
`the usage control policy and price tags, when rights are
`15 purchased again through the other information process(cid:173)
`ing apparatuses; and a sending step of sending the sec(cid:173)
`ond usage control status prepared by the second
`preparation step as well as the encrypted information
`and the key stored on the storage means to the other
`information processing apparatuses.
`[0007]
`Furthermore, the providing medium of the
`present invention provides a computer-readable pro(cid:173)
`gram for executing the process which comprises the
`first preparation step of preparing the first usage control
`status which identifies the first usage details describing
`the purchased rights and the pricing details correspond-
`ing to the first usage details; the storage step of storing
`the encrypted information, the first usage control status,
`the usage control policy that contains the second use
`type that describes the rights that can be purchased
`again based on the details of the purchased rights, the
`price tags that contain the pricing details corresponding
`to the second usage details, and the key needed to
`decrypt the encrypted information; the second prepara-
`tion step of preparing the second usage control status
`which identifies the second usage details and the pric(cid:173)
`ing details corresponding to the second usage details,
`based on the usage control policy and price tags, when
`rights are purchased again through the other informa-
`tion processing apparatuses; and the sending step of
`sending the second usage control status prepared by
`the second preparation step as well as the encrypted
`information and the key stored on the storage means to
`the other information processing apparatuses.
`[0008]
`Furthermore,
`the
`information processing
`apparatus, information processing method, and provid(cid:173)
`ing medium of the present invention prepare the first
`usage control status which identifies the first usage
`details describing the purchased rights and the pricing
`50 details corresponding to the first usage details; store the
`encrypted information, the first usage control status, the
`usage control policy that contains the second use type
`that describes the rights that can be purchased again
`based on the details of the purchased rights, the price
`tags that contain the pricing details corresponding to the
`second usage details, and the key needed to decrypt
`the encrypted information; prepare the second usage
`control status which identifies the second usage details
`
`Description
`
`Technical Field
`
`[0001]
`The present invention relates to an informa-
`tion processing apparatus,
`information processing
`method, and providing medium. More particularly, it
`relates to an information processing apparatus, infor(cid:173)
`mation processing method, and providing medium that
`utilize encrypted information.
`
`Background Art
`
`[0002]
`There are systems that encrypt information
`(hereafter referred to as content) such as music and
`send it to the information processing apparatus of the
`users who have made a required agreement, so that the
`users can decrypt and use the content on their informa-
`tion processing apparatus.
`[0003]
`If a user possesses two or more information
`processing apparatus, he/she must buy content and pay
`its usage charge for each information processing appa(cid:173)
`ratus. Even if content has been bought once, it must be
`bought again for the same charge if it is to be used on
`(bought for) a different information processing appara-
`tus.
`
`Disclosure of the Invention
`
`[0004]
`The present invention has been made in
`view of the above circumstances. It allows the user to
`buy the same content again at discount prices.
`[0005]
`To solve these problems, the present inven(cid:173)
`tion provides an
`information processing apparatus
`which comprises first preparation means for preparing
`first usage control status which identifies first usage
`details describing purchased rights and the pricing
`details corresponding to the first usage details; storage
`means for storing the encrypted information, the first
`usage control status, a usage control policy that con(cid:173)
`tains a second use type that describe the rights that can
`be purchased again based on the details of the pur(cid:173)
`chased rights, price tags that contain the pricing details
`corresponding to the second usage details, and the key
`needed to decrypt the encrypted information; second
`preparation means for preparing second usage control
`status which identifies the second usage details and the
`pricing details corresponding to the second usage
`details, based on the usage control policy and price
`tags, when rights are purchased again through another
`information processing apparatuses; and sending
`means for sending the second usage control status pre(cid:173)
`pared by the second preparation means as well as the
`encrypted information and the key stored on the storage
`means to the other information processing apparatuses.
`[0006]
`Also, the present invention provides an infor(cid:173)
`mation processing method which comprises a first prep(cid:173)
`aration step of preparing the first usage control status
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`EP 1 100 035 A1
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`4
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`and the pricing details corresponding to the second
`usage details, based on the usage control policy and
`price tags, when rights are purchased again through the
`other information processing apparatuses; and send the
`second usage control status prepared as well as the
`encrypted information and the key stored on the storage
`means to the other information processing apparatuses.
`[0009]
`Furthermore,
`the
`information processing
`apparatus of the present invention comprises receiving
`means
`for
`receiving,
`from
`the other
`information
`processing apparatuses, the encrypted information, the
`key needed to decrypt the encrypted information, and
`the usage control status which identifies the usage
`details describing the rights as well as the pricing details
`corresponding to the usage details; and execution
`means for executing the processes needed to use the
`information based on the rights described by the usage
`details identified by the usage control status.
`[0010]
`Furthermore,
`the
`information processing
`method of the present invention comprises a receiving
`step of receiving, from the other information processing
`apparatuses, the encrypted information, the key needed
`to decrypt the encrypted information, and the usage
`control status which identifies the usage details describ-
`ing the rights as well as the pricing details correspond-
`ing to the usage details; and an execution step of
`executing the processes needed to use the information
`based on the rights described by the usage details iden(cid:173)
`tified by the usage control status.
`[0011]
`Furthermore, the providing medium of the
`present invention provides a computer-readable pro(cid:173)
`gram for executing the process which comprises the
`receiving step of receiving, from the other information
`processing apparatuses, the encrypted information, the
`key needed to decrypt the encrypted information, and
`the usage control status which identifies the usage
`details describing the rights as well as the pricing details
`corresponding to the usage details; and the execution
`step of executing the processes needed to use the infor(cid:173)
`mation based on the rights described by the usage
`details identified by the usage control status.
`[0012]
`Furthermore,
`the
`information processing
`apparatus, information processing method, and provid-
`ing medium of the present invention receive, from the
`other
`information
`processing
`apparatuses,
`the
`encrypted information, the key needed to decrypt the
`encrypted information, and the usage control status
`which identifies the usage details describing the rights
`as well as the pricing details corresponding to the usage
`details; and execute the processes needed to use the
`information based on the rights described by the usage
`details identified by the usage control status.
`[0013]
`Furthermore,
`the
`information processing
`apparatus of the present invention comprises storage
`means for storing the encrypted information, the usage
`control policy that contains the usage details that
`describe purchasable rights, the price tags that contain
`the pricing details corresponding to the usage details,
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`3
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`and the key needed to decrypt the encrypted informa(cid:173)
`tion; preparation means for preparing the usage control
`status which identifies the usage details and the pricing
`details corresponding to the usage details, based on the
`usage control policy and price tags stored on the stor(cid:173)
`age means; and sending means for sending the usage
`control status prepared by the preparation means as
`well as the encrypted information and the key stored on
`the storage means to the other information processing
`apparatuses when the rights are purchased again by
`the other information processing apparatuses.
`[0014]
`Furthermore,
`the
`information processing
`method of the present invention comprises a storage
`step of storing the encrypted information, the usage
`control policy that contains the usage details that
`describe purchasable rights, the price tags that contain
`the pricing details corresponding to the usage details,
`and the key needed to decrypt the encrypted informa(cid:173)
`tion; a preparation step of preparing the usage control
`status which identifies the usage details and the pricing
`details corresponding to the usage details, based on the
`usage control policy and price tags stored by the stor(cid:173)
`age step; and a sending step of sending the usage con(cid:173)
`trol status prepared by the preparation step as well as
`the encrypted information and the key stored by the
`storage step, to the other information processing appa(cid:173)
`ratuses when the rights are purchased again by the
`other information processing apparatuses.
`[0015]
`Furthermore, the providing medium of the
`present invention provides a computer-readable pro(cid:173)
`gram for executing the process which comprises the
`storage step of storing the encrypted information, the
`usage control policy that contains the usage details that
`describe purchasable rights, the price tags that contain
`the pricing details corresponding to the usage details,
`and the key needed to decrypt the encrypted informa(cid:173)
`tion; the preparation step of preparing the usage control
`status which identifies the usage details and the pricing
`details corresponding to the usage details, based on the
`usage control policy and price tags stored by the stor(cid:173)
`age step; and the sending step of sending the usage
`control status prepared by the preparation step as well
`as the encrypted information and the key stored by the
`storage step, to the other information processing appa(cid:173)
`ratuses when the rights are purchased again by the
`other information processing apparatuses.
`[0016]
`Furthermore,
`the
`information processing
`apparatus, information processing method, and provid(cid:173)
`ing medium of the present invention store the encrypted
`information, the usage control policy that contains the
`usage details that describe purchasable rights, the price
`tags that contain the pricing details corresponding to the
`usage details, and the key needed to decrypt the
`encrypted information; prepare the usage control status
`which identifies the usage details and the pricing details
`corresponding to the usage details, based on the stored
`usage control policy and price tags; and send the pre(cid:173)
`pared usage control status as well as the encrypted
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`EP 1 100 035 A1
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`information and key stored, to the other information
`processing apparatuses when the rights are purchased
`again by the other information processing apparatuses.
`[0017]
`Furthermore,
`the
`information processing
`apparatus of the present invention comprises receiving
`means
`for
`receiving,
`from
`the other
`information
`processing apparatuses, the encrypted information, the
`key needed to decrypt the encrypted information, and
`the usage control status which identifies the first use
`type describing predetermined rights and the pricing
`details corresponding to the first use type; storage
`means for storing a usage control policy that contains
`the second usage details that describe the rights that
`can be purchased again based on the rights described
`by the first usage details identified by the usage control
`status received by the receiving means, and price tags
`that contain the pricing details corresponding to the sec-
`ond usage details; and first preparation means for pre(cid:173)
`paring second usage control status which identifies the
`second usage details and the pricing details corre-
`sponding to the second usage details, based on the
`usage control policy and price tags stored by the stor-
`age means.
`[0018]
`information processing
`the
`Furthermore,
`method of the present invention comprises a receiving
`step of receiving, from the other information processing
`apparatuses, the encrypted information, the key needed
`to decrypt the encrypted information, and the usage
`control status which identifies the first use type describ-
`ing predetermined rights and the pricing details corre-
`sponding to the first use type; a storage step of storing
`the usage control policy that contains the second usage
`details that describe the rights that can be purchased
`again based on the rights described by the first usage
`details identified by the usage control status received by
`the receiving step, and price tags that contain the pric-
`ing details corresponding to the second usage details;
`and a preparation step of preparing second usage con-
`trol status which identifies the second usage details and
`the pricing details corresponding to the second usage
`details, based on the usage control policy and price tags
`stored by the storage step.
`[0019]
`Furthermore, the providing medium of the
`present invention provides a computer-readable pro(cid:173)
`gram for executing the process which comprises the
`receiving step of receiving, from the other information
`processing apparatuses, the encrypted information, the
`key needed to decrypt the encrypted information, the
`usage control status which identifies the first use type
`describing predetermined rights and the pricing details
`corresponding to the first use type; the storage step of
`storing the usage control policy that contains the sec-
`ond usage details that describe the rights that can be
`purchased again based on the rights described by the
`first usage details identified by the usage control status
`received by the receiving step, arid price tags that con-
`tain the pricing details corresponding to the second
`usage details; and the preparation step of preparing
`
`second usage control status which identifies the second
`usage details and the pricing details corresponding to
`the second usage details, based on the usage control
`policy and price tags stored by the storage step.
`[0020]
`Furthermore,
`the
`information processing
`apparatus, information processing method, and provid(cid:173)
`ing medium of the present invention receive, from the
`other
`information
`processing
`apparatuses,
`the
`encrypted information, the key needed to decrypt the
`encrypted information, and the usage control status
`which identifies the first use type describing predeter(cid:173)
`mined rights and the pricing details corresponding to
`the first use type; store the usage control policy that
`contains the second usage details that describe the
`rights that can be purchased again based on the rights
`described by the first usage details identified by the
`usage control status received, and price tags that con(cid:173)
`tain the pricing details corresponding to the second
`usage details; and prepares the second usage control
`status which identifies the second usage details and the
`pricing details corresponding to the second usage
`details, based on the usage control policy and price tags
`stored.
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`Brief Description of Drawings
`
`[0021]
`
`Figure 1 is a system diagram illustrating a EMO
`system.
`Figure 2 is a system diagram illustrating the major
`information flow in the EMO system.
`Figure 3 is a block diagram showing the functional
`configuration of an EMO service center 1.
`Figure 4 is a schematic diagram illustrating the
`transmission of delivery keys Kd at the EMO serv(cid:173)
`ice center 1.
`Figure 5 is another schematic diagram illustrating
`the transmission of delivery keys Kd at the EMO
`service center 1.
`Figure 6 is another schematic diagram illustrating
`the transmission of delivery keys Kd at the EMO
`service center 1.
`Figure 7 is another schematic diagram illustrating
`the transmission of delivery keys Kd at the EMO
`service center 1.
`Figure 8 is a chart illustrating an example of system
`registration information.
`Figure 9 is a block diagram showing an example
`functional configuration of a content provider 2.
`Figure 1 O is a chart showing an example UCP.
`Figure 11 is a schematic diagram illustrating control
`transfer of content.
`Figure 12 is a schematic diagram illustrating first(cid:173)
`generation duplication.
`Figure 13 is a schematic diagram showing a con(cid:173)
`tent provider secure container.
`Figure 14 is a schematic diagram showing an
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`EP 1 100 035 A1
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`8
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`example authentication certificate of the content
`provider 2.
`Figure 15 is a block diagram showing the functional
`configuration of a service provider 3.
`Figure 16 is a chart showing example PTs.
`Figure 17 is a schematic diagram showing a service
`provider secure container.
`Figure 18 is a schematic diagram showing an
`example authentication certificate of the service
`provider 3.
`Figure 19 is a block diagram showing an example
`functional configuration of a receiver 51 in a user
`home network 5.
`Figure 20 is a schematic diagram showing an
`example authentication certificate of SAM 62 of the
`receiver 51.
`Figure 21 is a chart showing an example of UCS.
`Figure 22 is a schematic diagram illustrating the
`internal structure of the usage information storage
`63A in the external storage 63 of the receiver 51.
`Figure 23 is a chart showing an example of
`accounting information.
`Figure 24 is a chart showing the information stored
`in the memory module 73 of the receiver 51.
`Figure 25 is a chart illustrating reference informa-
`tion 51.
`Figure 26 is a chart showing an example registra(cid:173)
`tion list of the receiver 51.
`Figure 27 is a block diagram showing an example
`functional configuration of a receiver 201 in the user
`home network 5.
`Figure 28 is a chart illustrating reference informa(cid:173)
`tion 51.
`Figure 29 is a chart showing an example registra-
`tion list of the receiver 201.
`Figure 30 is a block diagram showing an example
`functional configuration of a receiver 301 in the user
`home network 5.
`Figure 31 is a chart illustrating reference informa(cid:173)
`tion 301.
`Figure 32 is a chart showing an example registra(cid:173)
`tion list of the receiver 301.
`Figure 33 is a flow chart illustrating process for utili(cid:173)
`zation of content.
`Figure 34 is a flow chart illustrating the process of
`sending delivery keys Kd from the EMO service
`center 1 to the content provider 2.
`Figure 35 is a flow chart illustrating a flow of mutual
`authentication between the content provider 2 and
`EMO service center 1.
`Figure 36 is a flow chart illustrating another flow of
`mutual authentication between the content provider
`2 and EMO service center 1.
`Figure 37 is a flow chart illustrating another flow of
`mutual authentication between the content provider
`2 and EMO service center 1.
`Figure 38 is a flow chart illustrating the process of
`sending a content provider secure container from
`
`the content provider 2 to the service provider 3.
`Figure 39 is a flow chart illustrating the process of
`sending a service provider secure container from
`the service provider 3 to the receiver 51.
`Figure 40 is a flow chart illustrating the process in
`which the receiver 51 receives the service provider
`secure container.
`Figure 41 is a flow chart illustrating the process in
`which the receiver 51 reproduces content.
`Figure 42 is a flow chart illustrating an account set(cid:173)
`tlement process.
`Figure 43 is a flow chart illustrating a repurchasing
`process.
`Figure 44 is a chart showing another example of
`UCS.
`Figure 45 is a chart showing another example of
`accounting information.
`Figure 46 is a flow chart illustrating another repur(cid:173)
`chasing process.
`Figure 47 is a chart showing another example of
`UCS.
`Figure 48 is a chart showing another example of
`accounting information.
`Figure 49 is a flow chart illustrating another repur(cid:173)
`chasing process.
`Figure 50 is a chart showing another example of
`UCS.
`Figure 51 is a chart showing another example of
`accounting information.
`
`Best Mode for Carrying Out the Invention
`
`[0022]
`An embodiment of the present invention will
`be described below.
`
`(1) Information distribution system
`
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`[0023]
`Figure 1 illustrates an EMO (electronic music
`distribution) system by the application of the present
`invention. The EMO system consists of the EMO service
`center 1 that manages individual pieces of equipment,
`content provider 2 that provides content, service pro(cid:173)
`vider 3 that provides predetermined services corre(cid:173)
`sponding to content, and user network 5 composed of
`the equipment (receiver 51, receiver 201, and receiver
`301 in this example) on which content is used.
`[0024]
`The content in an EMO system is digital data
`whose information itself has a value. In this example,
`one piece of content corresponds to music data equiva-
`lent to one piece of music. Besides music data, how(cid:173)
`ever, content can be video data, game programs,
`computer programs, literary data, etc.
`[0025]
`The EMO service center 1 sends the deliv-
`ery keys Kd needed to use content to the user home
`55 network 5 and content provider 2, as shown in Figure 2,
`which shows the major information flow in the EMO sys(cid:173)
`tem. Also, the EMO service center 1 receives account(cid:173)
`ing information and the like from the user home network
`
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`EP 1 100 035 A1
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`5 and adjust charges.
`[0026]
`The content provider 2 possesses the con(cid:173)
`tent (encrypted with a content key Keo) to be provided,
`content key Keo (encrypted with a delivery key Kd)
`needed to decrypt the content, and usage control policy
`(abbreviated as UCP hereafter) that describes the
`usage details of content, and supplies them in the form
`called a content provider secure container (described
`later) to the service provider 3.
`[0027]
`The service provider 3 prepares one or more
`price tags (abbreviated as PT hereafter) according to
`the usage details contained in the UCP supplied by the
`content provider 2. The service provider 3 sends the
`prepared PT(s) together with the content (encrypted
`with a content key Keo), content key Keo (encrypted
`with a delivery key Kd), and UCP supplied by the con-
`tent provider 2, in the form called a service provider
`secure container to the user home network 5 through a
`network 4 consisting of a private cable network, the
`Internet, or communications satellites.
`[0028]
`The user home network 5 prepares usage
`control status (abbreviated as UCS hereafter) according
`to the supplied UCP and PT(s) and performs the proc-
`ess of using the content based on the prepared UCS.
`Also, the user home network 5 prepares accounting
`information, timed with the preparation of UCS, and
`sends it together with corresponding UCP and PT(s) to
`the EMO service center 1, timed with, for example, the
`provision of the delivery keys Kd.
`
`(2) EMO service center
`
`[0029]
`Figure 3 is a block diagram showing the
`functional configuration of the EMO service center 1.
`The service provider management section 11 supplies
`profit-sharing information to the service provider 3. The
`content provider management section 12 sends deliv-
`ery keys Kd and supplies profit-sharing information to
`the content provider 2.
`[0030]
`The copyright management section 13
`sends information about the usage of content by the
`user home network 5 to the appropriate copyright man(cid:173)
`agement body, for example, JASPAC (Japanese Society
`for Rights of Authors, Composers and Publishers).
`[0031]
`The key server 14 stores delivery keys Kd
`and supplies it to the content provider 2 through the
`content provider management section 12 or to the user
`home network 5 through the user management section
`18.
`[0032]
`The delivery keys Kd supplied to the user
`home network 5 equipment and content provider 2 from
`the EMO service center 1 will be described with refer(cid:173)
`ence to Figures 4 to 7.
`[0033]
`Figure 4 shows the delivery keys Kd pos(cid:173)
`sessed by the EMO service center 1, the delivery keys
`Kd possessed by the content provider 2, and the deliv(cid:173)
`ery keys Kd possessed by the receiver 51 in January
`1998 when the content provider 2 starts to provide con-
`
`5
`
`10
`
`15
`
`25
`
`35
`
`tent and the receiver 51 composing the user home net(cid:173)
`work 5 starts to use the content.
`[0034]
`In the example of Figure 4, a delivery key Kd
`is valid from the first day to the last day of a calendar
`month (both inclusive) . For example, the delivery key
`Kd version 1 with a value of "aaaaaaaa" consisting of a
`fixed random number of bits is available from January 1,
`1998 to January 31, 1998 both inclusive (i.e., the con(cid:173)
`tent key Keo that encrypt the content distributed to the
`user home network 5 via the service provider 3 from
`January 1, 1998 to January 31, 1998 is encrypted with
`the delivery key Kd version 1 ). The delivery key Kd ver(cid:173)
`sion 2 with a value of "bbbbbbbb" consisting of a fixed
`random number of bits is available from February 1,
`1998 to February 28, 1998 both inclusive (i.e., the con(cid:173)
`tent key Keo that encrypt the content distributed to the
`user home network 5 via the service provider 3 during
`the given period is encrypted by the delivery key Kd ver(cid:173)
`sion 2). Similarly, the delivery key Kd version 3 is avail-
`20 able during March 1998, the delivery key Kd version 4 is
`available during April 1998, the delivery key Kd version
`5 is available during May 1998, and the delivery key Kd
`version 6 is available during June 1998.
`[0035]
`Before the content provider 2 starts to pro(cid:173)
`vide content, the EMO service center 1 sends six deliv(cid:173)
`ery keys Kd -- delivery keys Kd versions 1 to 6 --
`available from January 1998 to June 1998 (both inclu(cid:173)
`sive) to the content provider 2, which receives and
`stores the six delivery keys Kd. The reason why six
`30 months' delivery keys Kd are stored is that a certain
`period of time is required for the content provider 2 to
`make preparations such as encryption of the content
`and content keys before starting to provide the content.
`[0036]
`Before the receiver 51 starts to use content,
`the EMO service center 1 sends three delivery keys Kd
`-- delivery keys Kd versions 1 to 3 --available from Jan(cid:173)
`uary 1998 to March 1998 (both inclusive) to the receiver
`51, which receives and stores the three delivery keys
`Kd. Three months' delivery keys Kd are stored in order
`to avoid the situation in which content would not be
`available even during the term of the contract due to
`trouble in that the receiver 5 cannot be connected to the
`EMO service center 1 or other trouble and to reduce the
`load on the user home network 5 by decreasing the
`number of connections to the EMO service center 1.
`[0037]
`During the period from January 1, 1998 to
`January 31, 1998, the delivery key Kd version 1 is used
`by the EMO service center 1, the content provider 2,
`and the receiver 51 that composes the user home net(cid:173)
`work 5.
`[0038]
`Now the transmission of delivery keys Kd
`from the EMO service center 1 to the content provider 2
`and receiver 51 on February 1, 1998 will be described
`with reference to Figure 5. The EMO service center 1
`55 sends six delivery keys Kd -- delivery keys Kd versions
`2 to 7 -- available from February 1998 to July 1998 (both
`inclusive) to the content provider 2, which receives the
`six delivery keys Kd and store them overwriting the
`
`40
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`45
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`50
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`6
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`Page 6 of 84
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`11
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`EP 1 100 035 A1
`
`12
`
`existing ones. The EMO service center 1 sends three
`delivery keys Kd
`delivery keys Kd versions 2 to 4
`available from February 1998 to April 1998 (both inclu(cid:173)
`sive) to the receiver 51, which receives the three deliv(cid:173)
`ery keys Kd and store them overwriting the existing
`ones. The EMO service center 1 stores the delivery key
`Kd version 1 as it is. This is done to make past delivery
`keys Kd available for use in case of unexpected trouble
`or in case an illegal act is committed or detected.
`[0039]
`During the period from February 1, 1998 to
`February 28, 1998, the delivery key Kd version 2 is used
`by the EMO service center 1, the content provider 2,
`and the receiver 51 that composes the user home net(cid:173)
`work
`[0040]
`Now the transmission of delivery keys Kd
`from the EMO service center 1 to the content provider 2
`and receiver 51 on March 1, 1998 will be described with
`reference to Figure 6. The EMO service center 1 sends
`six delivery keys Kd -- deliver