COMMUNICATION APPARATUS, KEY SERVER, AND MANAGEMENT SERVER
First Claim
1. A communication apparatus that receives a plurality of pieces that constitute a part of a content, comprising:
- an information obtaining unit that obtains file information indicating all or a part of the first and the second encrypted pieces and version management information capable of judging whether the file information has validity;
a content receiving unit that receives, for each of the pieces, one of a first encrypted piece and a second encrypted piece from another communication apparatus by using the file information, a plurality of first encrypted pieces being obtained by encrypting the pieces with a first encryption key, the second encrypted piece being obtained by encrypting at least one of the pieces with a second encryption key, and the first encryption key and the second encryption key for encrypting a same piece being different from each other;
a transmitting unit that transmits, to a key server, a request message for requesting decryption keys each of which is used for decrypting the one of the first encrypted piece and the second encrypted piece received by the content receiving unit for a different one of the pieces and the version management information of the file information used to obtain the one of the first encrypted piece and the second encrypted piece in correspondence with each of the pieces; and
a key receiving unit that receives the decryption keys provided by the key server in response to the request message.
1 Assignment
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Accused Products
Abstract
A communication apparatus obtains file information indicating all or a part of first and second encrypted pieces obtained by encrypting a plurality of pieces constituting a part of a content and version management information with which it is possible to judge whether the file information has validity and receives, for each of the pieces, one of the first encrypted piece and the second encrypted piece from another communication apparatus, by using the file information. The communication apparatus transmits, to a key server, a request message for requesting decryption keys each being used for decrypting the one of the first encrypted piece and the second encrypted piece received for a different one of the pieces and the version management information of the file information used to obtain the one of the first encrypted piece and the second encrypted piece in correspondence with each of the pieces and receives the decryption keys.
109 Citations
25 Claims
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1. A communication apparatus that receives a plurality of pieces that constitute a part of a content, comprising:
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an information obtaining unit that obtains file information indicating all or a part of the first and the second encrypted pieces and version management information capable of judging whether the file information has validity; a content receiving unit that receives, for each of the pieces, one of a first encrypted piece and a second encrypted piece from another communication apparatus by using the file information, a plurality of first encrypted pieces being obtained by encrypting the pieces with a first encryption key, the second encrypted piece being obtained by encrypting at least one of the pieces with a second encryption key, and the first encryption key and the second encryption key for encrypting a same piece being different from each other; a transmitting unit that transmits, to a key server, a request message for requesting decryption keys each of which is used for decrypting the one of the first encrypted piece and the second encrypted piece received by the content receiving unit for a different one of the pieces and the version management information of the file information used to obtain the one of the first encrypted piece and the second encrypted piece in correspondence with each of the pieces; and a key receiving unit that receives the decryption keys provided by the key server in response to the request message. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A communication apparatus that receives a plurality of pieces that constitute a part of a content, comprising:
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a content receiving unit that receives, for each of the pieces, one of a first encrypted piece and a second encrypted piece from another communication apparatus, a plurality of first encrypted pieces being obtained by encrypting the pieces with a first encryption key, the second encrypted piece being obtained by encrypting at least one of the pieces with a second encryption key, and the first encryption key and the second encryption key for encrypting a same piece being different from each other; a key request transmitting unit that transmits, to a key server storing decryption keys, a request message for requesting the decryption keys each of which is used for decrypting the one of the first encrypted piece and the second encrypted piece received by the content receiving unit for a different one of the pieces; a request receiving unit that receives, from the key server, an information request message for requesting storing proof information to prove that the communication apparatus stores the encrypted pieces that are to be decrypted by using the decryption keys requested in the request message and each of which is the one of the first encrypted piece and the second encrypted piece corresponding to a different one of the pieces; an information transmitting unit that transmits the storing proof information to the key server in response to the information request message; and a key receiving unit that receives all or a part of the decryption keys provided by the key server based on the storing proof information and the request message. - View Dependent Claims (11, 12)
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13. A key server that communicates with a communication apparatus that receives a plurality of pieces that constitute a part of a content, comprising:
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a request receiving unit that receives, from the communication apparatus, a request message for requesting decryption keys each of which is used for decrypting the one of a first encrypted piece and a second encrypted piece corresponding to a different one of the pieces and version management information capable of judging whether file information has validity, a plurality of first encrypted pieces being obtained by encrypting the plurality of pieces each with a first encryption key, one or more second encrypted pieces being obtained by encrypting one or more of the plurality of pieces each with a second encryption key, for each of the pieces, the first encryption key being different from the second encryption key, the communication apparatus receives, for each of the pieces, one of the first encrypted piece and the second encrypted piece from another communication apparatus, and the file information having been used to obtain the one of the first encrypted piece and the second encrypted piece in correspondence with each of the pieces; a first storage unit that stores the decryption keys; a second storage unit that stores validity information used for identifying the version management information of one or more pieces of file information having validity; a judging unit that judges whether the decryption keys requested in the request message are valid by using the received version management information and the validity information; a determining unit that determines whether the decryption keys should be transmitted, based on a combination of the decryption keys requested in the request message, when the judging unit has judged that the decryption keys are valid; and a key transmitting unit that reads the decryption keys corresponding to the combination requested in the request message from the first storage unit and transmits the read decryption keys to the communication apparatus, when the determining unit has determined that the decryption keys should be transmitted. - View Dependent Claims (14, 15, 16)
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17. A key server that communicates with a communication apparatus that receives a plurality of pieces that constitute a part of a content, comprising:
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a request receiving unit that receives, from the communication apparatus, a request message for requesting decryption keys each of which is used for decrypting the one of a first encrypted piece and a second encrypted piece corresponding to a different one of the pieces, a plurality of first encrypted pieces being obtained by encrypting the plurality of pieces each with a first encryption key, one or more second encrypted pieces being obtained by encrypting one or more of the plurality of pieces each with a second encryption key, for each of the pieces, the first encryption key being different from the second encryption key, the communication apparatus receives, for each of the pieces, one of the first encrypted piece and the second encrypted piece from another communication apparatus; a first storage unit that stores the decryption keys; a second storage unit that stores storing judgment information used for judging whether the communication apparatus stores encrypted pieces that are to be decrypted by using the decryption keys requested in the request message and each of which is the one of the first encrypted piece and the second encrypted pieces corresponding to a different one of the pieces; a request transmitting unit that transmits, to the communication apparatus, an information request message for requesting storing proof information to prove that the communication apparatus stores the encrypted pieces that are to be decrypted by using the decryption keys requested in the request message and each of which is the one of the first encrypted piece and the second encrypted pieces corresponding to a different one of the pieces; an information receiving unit that receives the storing proof information from the communication apparatus; a storing proof judging unit that judges whether the communication apparatus stores the encrypted pieces that are to be decrypted by using the decryption keys requested in the request message and each of which is the one of the first encrypted piece and the second encrypted piece corresponding to a different one of the pieces, by using the received storing proof information and the stored storing judgment information; a determining unit that determines whether the decryption keys should be transmitted, based on a combination of the decryption keys requested in the request message, when the storing proof judging unit has judged that the communication apparatus stores the encrypted pieces; and a key transmitting unit that reads the decryption keys corresponding to the combination requested in the request message from the first storage unit and transmits the read decryption keys to the communication apparatus, when the determining unit has determined that the decryption keys should be transmitted. - View Dependent Claims (18, 19, 20)
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21. A management server that communicates with a communication apparatus that receives a plurality of pieces that constitute a part of a content, comprising:
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a first storage unit that stores connection destination information used for accessing the another communication apparatus, a plurality of first encrypted pieces being obtained by encrypting the plurality of pieces each with a first encryption key, one or more second encrypted pieces being obtained by encrypting one or more of the plurality of pieces each with a second encryption key, for each of the pieces, the first encryption key being different from the second encryption key, file information indicates all or a part of the first and the second encrypted pieces and is in correspondence with version management information with which it is possible to judge whether the file information has validity, the communication apparatus receives, for each of the pieces, one of the first encrypted piece and the second encrypted piece from another communication apparatus, by using the file information; and an information transmitting unit that transmits the connection destination information used for accessing the another communication apparatus, when the communication apparatus has accessed the management server by using first access information that is in correspondence with the file information and is used for accessing the management server. - View Dependent Claims (22, 23, 24, 25)
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Specification