JP5284119B2 - Server, information processing method and program - Google Patents

Description

  The present invention relates to a server, an information processing method, and a program.

  In content distribution using P2P (Peer-to-Peer) technology, it is expected that the distribution cost of a service provider is suppressed by performing secondary distribution of content received by a terminal to another terminal. In order to promote secondary distribution and reduce distribution costs, it is important to provide incentives to users of terminals that are responsible for secondary distribution. In recent years, various techniques for providing such incentives have been developed (see, for example, Patent Documents 1 to 4). In the technique of Patent Document 1, a primary distribution server that first performs transmission is transmitted with a higher priority to a terminal that has selected to perform secondary distribution in P2P. With the technology of Patent Document 2, the amount of content charging is reduced for a terminal that has selected to take charge of secondary delivery in P2P. In the technique of Patent Literature 3, a terminal responsible for secondary distribution notifies the server that provides the service of the distribution volume of the secondary distribution in advance and receives incentive payment. In the technique of Patent Document 4, as a technique for distributing profits to a distributor that mediates distribution, when route information specifying a terminal that mediates distribution is secondarily distributed together with content, and a terminal that reproduces the content acquires a license key The route information is notified to the license server, and the profit is distributed to the terminals specified by the route information.

  By the way, in order to suppress the distribution cost even if the distribution amount increases, each terminal responsible for the secondary distribution needs to bear a distribution amount that is equal to or greater than the reception amount on average. On the other hand, even if each terminal is responsible for secondary delivery of P2P, there is a case where the capacity of the uplink is insufficient, or there is a case where the terminal is disconnected from the network early after downloading. There is. In the P2P technology, in many cases, one terminal is divided into a plurality of pieces, and each terminal receives each piece from a plurality of terminals, thereby improving efficiency and fault tolerance. In this case, the amount of distribution is different even for terminals that carry the same secondary distribution.

Japanese Patent No. 3962372 Japanese Patent No. 41277753 Japanese Patent No. 4066448 JP 2002-229960 A

  However, in the techniques of Patent Documents 1 to 4, since incentives cannot be given according to the distribution amount, there is a fear that it may not lead to encouragement of a terminal responsible for a sufficient amount of secondary distribution. In particular, it has been difficult to increase the incentive to the terminal that secondarily distributes the last piece. For example, when the content is played back by the streaming method, the playback may be stopped in the middle, so that there are few terminals holding the last piece compared to the top of the content. Moreover, even if the terminal holds the last piece, the possibility of secondary distribution is reduced if the time until the network disconnection after the end of reproduction is short. Further, in the technique of Patent Document 3, when the transmission source terminal notifies the server of the amount of secondary delivery, there is a risk of fraud such as notifying of the amount of delivery actually delivered more than the secondary delivery. .

  The present invention has been made in view of the above, and in a data distribution system that distributes pieces that are a part of data, an incentive according to a distribution amount can be given to a communication device that has performed transmission. An object of the present invention is to provide a server, an information processing method, and a program that are capable of preventing fraud.

  In order to solve the above-described problems, the present invention is a server, wherein a piece is a part of data, is encrypted by a communication device, and transmitted from the communication device to the other communication device, The key request for requesting a decryption key for decrypting the piece includes data identification information for identifying the data and key generation information for generating the decryption key, and the other Obtained from the communication device, wherein the key generation information includes device identification information assigned to the communication device, and acquires the data identification information and the key generation information included in the key request Means, using the data identification information and the key generation information, a first calculation means for calculating a delivery amount that is a data amount of the piece transmitted by the communication device, and using the delivery amount, Communication device A second calculating means for calculating a reward point given for, characterized by comprising a first storage means for storing the reward points in association with the device identification information.

  The present invention is also an information processing method executed by a server, wherein a piece is a part of data, is encrypted by a communication device, and is transmitted from the communication device to the other communication device. The key request for requesting a decryption key for decrypting the piece includes data identification information for identifying the data and key generation information for generating the decryption key, and The key generation information is transmitted from another communication device, and includes the device identification information allocated to the communication device, and acquires the data identification information and the device identification information included in the key request. A first calculation step of calculating a distribution amount that is a data amount of the piece transmitted by the communication device using the data identification information and the key generation information, and using the distribution amount. A second calculation step of calculating reward points to be given to the communication device, and a first storage control step of storing the reward points in association with the device identification information in a storage means. To do.

  The present invention is also a program, wherein a piece is a part of data, is encrypted by a communication device, transmitted from the communication device to the other communication device, and decrypts the piece A key request for requesting a decryption key includes data identification information for identifying the data and key generation information for generating the decryption key, and is transmitted from the other communication device. The key generation information includes device identification information assigned to the communication device, and obtains the data identification information and the key generation information included in the key request, and the data First identification means for calculating a distribution amount that is a data amount of the piece transmitted by the communication device using the identification information and the key generation information, and using the distribution amount, the communication device Grant That a second calculating means for calculating a reward points, causes a computer to the reward points as first storage control means for storing in the storage means in association with the device identification information.

  Advantageous Effects of Invention According to the present invention, in a data distribution system that distributes pieces that are part of data, it is possible to give an incentive according to the distribution amount to a communication device that has transmitted, and to prevent fraud Become.

FIG. 1 is a diagram illustrating a configuration of a data distribution system according to the first embodiment. FIG. 2 is a diagram illustrating a functional configuration of the node 50 according to the embodiment. FIG. 3 is a diagram illustrating a functional configuration of the node 51 according to the embodiment. FIG. 4 is a diagram schematically showing information transmitted from the node 50 to the node 51A according to the embodiment. FIG. 5 is a diagram schematically illustrating information transmitted from the node 51A to the node 51B according to the embodiment. FIG. 6 is a diagram schematically illustrating information transmitted from the node 51A to the node 51B according to the embodiment. FIG. 7 is a diagram schematically illustrating information transmitted from the node 51B to the key server 53 according to the embodiment. FIG. 8 is a diagram schematically showing information transmitted from the key server 53 to the node 51B according to the embodiment. FIG. 9 is a diagram schematically showing information transmitted from the key server 53 to the node 51B according to the embodiment. FIG. 10 is a diagram illustrating a functional configuration of the key server 53 according to the embodiment. FIG. 11 is a diagram illustrating the price of each distribution data stored in the price information storage unit 539 according to the embodiment. FIG. 12 is a diagram illustrating the total of reward points stored in the reward point storage unit 541 according to the embodiment. FIG. 13 is a diagram illustrating piece information stored in the piece information storage unit 535 according to the embodiment. FIG. 14 is a diagram illustrating conversion points stored in the reward point conversion information storage unit 540. FIG. 15 is a flowchart showing a procedure of distribution processing performed by the node 50 which is the distribution start node according to the embodiment. FIG. 16 is a flowchart illustrating a procedure of a reception process in which the node 51 according to the embodiment receives an encrypted piece from the node 50 or another node 51. FIG. 17 is a diagram schematically illustrating information received by the node according to the embodiment. FIG. 18 is a flowchart showing a procedure of distribution processing performed by a node 51 other than the distribution start node according to the embodiment. FIG. 19 is a diagram schematically illustrating information transmitted by the node according to the embodiment. FIG. 20 is a flowchart illustrating a procedure of a decryption process in which the node 51 according to the embodiment acquires a decryption key from the key server 53 and decrypts the encrypted piece using the decryption key. FIG. 21 is a diagram schematically illustrating information transmitted by the node according to the embodiment. FIG. 22 is a diagram schematically illustrating a symmetric key received by the node according to the embodiment. FIG. 23 is a flowchart illustrating a key transmission process procedure in which the key server 53 according to the embodiment transmits a decryption key in response to a key request from the node 51. FIG. 24 is a flowchart showing the procedure of the accounting process according to the embodiment. FIG. 25 is a flowchart showing a procedure of reward point calculation processing according to the embodiment. FIG. 26 is a flowchart showing the procedure of the decryption key generation process according to the embodiment. FIG. 27 is a flowchart of a reward point calculation process performed when the key server 53 according to the second embodiment performs a key transmission process. FIG. 28 is a diagram illustrating conversion points and weighting factors stored in the reward point conversion information storage unit 540 according to the third embodiment. FIG. 29 is a flowchart illustrating a procedure of reward point calculation processing performed when the key server 53 according to the embodiment performs key transmission processing. FIG. 30 is a diagram exemplifying prices and exchange points stored in the price information storage unit 539 according to a modification. FIG. 31 is a flowchart showing the procedure of the billing process according to the modification. FIG. 32 is a flowchart illustrating a procedure of key transmission processing according to a modification. FIG. 33 is a diagram illustrating the reward points stored in the reward point storage unit 541 according to a modification.

Exemplary embodiments of a server, an information processing method, and a program according to the present invention are explained in detail below with reference to the accompanying drawings.
[First embodiment]
(1) Configuration <Data distribution system configuration>
FIG. 1 is a diagram showing a configuration of a data distribution system according to the present embodiment. In the data distribution system according to the present embodiment, a plurality of nodes 50, 51A to 51B are connected via a P2P network NT. Although not shown, other nodes can also be connected via the P2P network NT. Each node 50, 51 </ b> A to 51 </ b> B is connected to the key server 53. Each of the nodes 50 and 51A to 51B holds a node ID, which is device identification information uniquely assigned to each node, and a secret key as assignment information uniquely assigned to each node. The node IDs assigned to the nodes 50, 51A to 51B are ID # 0, ID # 1, and ID # 2, respectively, and the secret keys are s_0, s_1, and s_2, respectively. Of the nodes 50 and 51A to 51B, the node 50 is a distribution start node serving as a data distribution base, and holds data to be distributed (referred to as distribution data). The distribution data may be plaintext or already encrypted ciphertext. For example, the distribution data may be video data protected by some DRM (Digital Right Management) System as encryption. The key server 53 holds a secret key assigned to each of the nodes 50 and 51A to 51B. Hereinafter, when it is not necessary to distinguish the nodes 51A to 51B, they are simply referred to as the node 51.

  Here, the hardware configuration of each device including the nodes 50 and 51 and the key server 53 will be described. Each device is a control device such as a CPU (Central Processing Unit) that controls the entire device, a storage device such as a ROM (Read Only Memory) or a RAM (Random Access Memory) that stores various data and various programs, and a variety of devices. It has an external storage device such as an HDD (Hard Disk Drive) or CD (Compact Disk) drive device that stores data and various programs, and a bus that connects them, and has a hardware configuration that uses a normal computer. ing. Each device includes a display device that displays information, an input device such as a keyboard and a mouse that accepts user instruction input, and a communication I / F (interface) that controls communication with an external device. Connected by.

<Configuration of distribution start node>
Next, in the hardware configuration described above, various functions realized when the CPU of the node 50 that is the distribution start node executes various programs stored in the storage device or the external storage device will be described. FIG. 2 is a diagram illustrating a functional configuration of the node 50. The node 50 includes a unique information storage unit 500, a random number generation unit 501, a temporary symmetric key generation unit 502, a piece encryption unit 503, a piece generation unit 504, a data transmission unit 505, and a transmission request reception unit 506. Have The unique information storage unit 500 is reserved as a storage area in an external storage device such as an HDD of the node 50, for example. The entity of the random number generation unit 501, the temporary symmetric key generation unit 502, the piece generation unit 504, the piece encryption unit 503, the data transmission unit 505, and the transmission request reception unit 506 is executed by the CPU of the node 50. Sometimes generated on a storage device such as a RAM. Note that distribution data is stored in advance in the external storage device of the node 50.

  The unique information storage unit 500 stores the node ID and secret key assigned to the node 50. The piece unit 504 divides the distribution data into a plurality of pieces. As a division method, for example, there is a method of dividing distribution data from the beginning for each fixed data size, but the method is not limited thereto. When distribution data is divided with a fixed data size, the remainder may be the last piece, and only the data size of this last piece may be variable, or dummy data may be inserted as padding for the remainder. The last piece may be formed and the data size of each piece may be fixed. The data size of each piece is shared with the key server 53 in advance. The sharing method is not particularly limited, for example, by file copy or communication via a network. Each distribution data is pre-assigned a content type ID (CID) for identifying each distribution data, and the piece unit 504 assigns the content type ID of the distribution data when dividing the distribution data. Assume that each piece is associated with each piece. Further, when the piece unit 504 divides the distribution data, piece specifying information for specifying each piece is assigned to each piece. Specifically, the piece unit 504 assigns a piece number to each piece in order from the head to the tail when dividing the distribution data. This piece number is piece specifying information that specifies which part of the distribution data each piece is. The piece unit 504 may write the content type ID and the piece number in a piece header, for example, or may add the content type ID and piece number separately to the piece without being encrypted.

  The transmission request receiving unit 506 receives a piece request for requesting the piece divided by the piece forming unit 504 from the other node 51. When the transmission request reception unit 506 receives a piece request, the random number generation unit 501 generates a random number that is temporary information that can be different for each occurrence. The temporary information only needs to be a value that can be different every time it is generated at the node, and is, for example, a random number, a time stamp, a communication sequence number, a counter value unique to the node, or a time variant parameter. The Time Variant Parameter is described in, for example, the document ISO9798-1.

Temporary symmetric key generation unit 502 generates a temporary symmetric key by function F using the random number generated by random number generation unit 501 and the private key stored in unique information storage unit 500. This can be expressed by the following formula.
k_0 = F (s_0, r_0)

  Note that the function F is a one-way function, a common key encryption, or a pseudo-random number generator, and even if a secret key or random number that is an input value is known, a temporary symmetric key that is an output value cannot be estimated from these. is there. The temporary symmetric key is a function F, and it is only necessary that the relationship between the input value and the output value of the function F is uniquely determined. For example, it may be a hash function such as SHA-1 or SHA256, such as AES, Hiercrypt. Or a pseudo-random number generator such as Mersenne twister. A value obtained by combining a random number and a secret key may be input to the hash function. In the common key cryptosystem, the random number may be encrypted with a secret key, or the secret key may be encrypted with a random number. In the common key cryptosystem, the random number may be decrypted with the secret key, or the secret key may be decrypted with the random number. A value obtained by combining a random number and a secret key may be input to the pseudo-random number generator.

  The piece encryption unit 503 encrypts the piece using the temporary symmetric key generated by the temporary symmetric key generation unit 502 and outputs an encrypted piece. The temporary symmetric key is also an encryption key used for encryption, and is also a decryption key for decrypting the encryption performed on the encrypted piece. The data transmission unit 505 outputs the node ID stored in the unique information storage unit 500, the random number generated by the random number generation unit 501, and the piece encryption unit 503 to the other node 51 that has transmitted the piece request. And send the encrypted piece.

<Configuration of nodes other than the distribution start node>
Next, various functions realized when the CPU of the node 51 other than the distribution start node executes various programs stored in the storage device or the external storage device will be described. FIG. 3 is a diagram illustrating a functional configuration of the node 51. The node 51 includes a unique information storage unit 510, a random number generation unit 511, a temporary symmetric key generation unit 512, a piece encryption unit 513, a data reception unit 514, a data transmission unit 515, and a transmission request reception unit 516. A data storage unit 517, a transmission request transmission unit 518, a key request transmission unit 519, a piece decryption unit 520, an encryption determination unit 521, and a random number alternative generation unit 522. The unique information storage unit 510 and the data storage unit 517 are reserved as storage areas in an external storage device such as an HDD of the node 51, for example. Random number generation unit 511, temporary symmetric key generation unit 512, piece encryption unit 513, data transmission unit 515, transmission request reception unit 516, data reception unit 514, key request transmission unit 519, piece decryption unit The entities 520, the encryption determination unit 521, and the random number alternative generation unit 522 are generated on a storage device such as a RAM when the CPU of the node 51 executes the program.

  The unique information storage unit 510 stores the node ID and secret key assigned to the node 51. The configuration of the transmission request receiving unit 516 is the same as the configuration of the transmission request receiving unit 506 included in the node 50 described above. The transmission request transmission unit 518 transmits a piece request for requesting a piece to the node 50 or another node 51. The data reception unit 514 transmits at least the encrypted piece in which the piece is encrypted and the transmission of the encrypted piece from the node 50 or another node 51 to which the transmission request transmission unit 518 has transmitted the piece request. A node ID sequence including each node ID assigned to one other node 50, 51 and a random number sequence including each random number generated by the other node 50, 51 are received. This random number includes a random number used to generate a temporary symmetric key used for encryption of the piece and a randomly generated random number (referred to as an alternative random number). The latter will be described later. The data storage unit 517 stores the node ID sequence, the random number sequence, and the encrypted piece received by the data reception unit 514 in association with each other.

  When the transmission request reception unit 516 receives a piece request from another node 51, the encryption determination unit 521 determines whether to encrypt the transmission target encrypted piece according to a predetermined probability. The predetermined probability value is stored in, for example, an external storage device. The random number generation unit 511 generates a random number when the encryption determination unit 521 determines to encrypt the encrypted piece to be transmitted. When the encryption determination unit 521 determines that the encrypted piece to be transmitted is encrypted, the temporary symmetric key generation unit 512 generates the random number generated by the random number generation unit 511, the secret key stored in the unique information storage unit 510, and Is used to generate a temporary symmetric key by the function F described above. The piece encryption unit 513 is stored in the data storage unit 517 using the temporary symmetric key generated by the temporary symmetric key generation unit 512 when the encryption determination unit 521 determines that the encrypted piece to be transmitted is encrypted. One encrypted piece is further encrypted, and a new encrypted piece is output.

  When the encryption determining unit 521 determines that the encrypted piece to be transmitted is not encrypted, the random number alternative generation unit 522 stores a node string associated with the encrypted piece and stored in the data storage unit 517, and An alternative random number is generated by the function F using the secret key stored in the unique information storage unit 510.

For example, it is assumed that node ID string ID # 0,..., ID # (j−1) (j is an integer of 1 or more) is stored in the data storage unit 517 of the node 51A. The unique information storage unit 510 stores a secret key s_1. The alternative random number generated here is expressed as follows as r_1.
r_1 = F (s_1, ID # 0,…, ID # (j-1))
The function F is a one-way function, a common key encryption, or a pseudo-random number generator, and cannot secrete a secret key or a node string that is an input value from a random number that is an output result.

  The data transmission unit 515 transmits the following data according to the determination result of the encryption determination unit 521 to the other node 51 that has transmitted the piece request received by the transmission request reception unit 516. When the encryption determining unit 521 determines that the encrypted piece to be transmitted is encrypted, the data to be transmitted is associated with the node ID string stored in the data storage unit 517 in association with the encrypted piece, and the unique information A new node ID sequence including the node ID stored in the storage unit 510 and a new random number generated by the random number generation unit 511 in addition to the random number sequence associated with the encrypted piece and stored in the data storage unit 517 Random number sequence and a new encrypted piece output by the piece encryption unit 513. The data transmitted when the encryption determining unit 521 determines that the encrypted piece to be transmitted is not encrypted is unique in addition to the node ID string stored in the data storage unit 517 in association with the encrypted piece. The alternative node ID generated by the random number alternative generation unit 522 in addition to the new node ID sequence including the node ID stored in the information storage unit 510 and the random number sequence associated with the encrypted piece and stored in the data storage unit 517 A new random number sequence including a random number and the encrypted piece stored in the data storage unit 517. When the encrypted piece is not stored in the data storage unit 517, even if the transmission request receiving unit 516 receives the piece request, the piece encryption unit 513 does not output the encrypted piece, and the data transmission unit 515 does not send the encrypted piece.

  Here, the node ID sequence, the random number sequence, and the encrypted piece transmitted from the nodes 50 and 51 will be specifically described. In addition, although the node ID and the random number transmitted together with this from the node 50 to one encrypted piece are one each, here, for convenience of explanation, these may be described as a node sequence and a random number sequence, respectively. . Here, a case will be described in which the encrypted piece is transmitted from the node 50 to the node 51A, the encrypted piece is transmitted from the node 51A to the node 51B, and the key request is transmitted from the node 51B to the key server 53. In this case, the node 51A performs encryption and the node 51A does not perform encryption. First, the former case will be described. For example, in response to a piece request from the node 51A for a piece P, the node 50 generates a temporary symmetric key k_0 using a random number r_0 and a secret key s_0, and encrypts the piece P using this to encrypt the piece P Suppose that piece EP (k_0) P is output. Then, it is assumed that the node 50 transmits the encrypted piece EP (k_0) P together with the node ID ID # 0 and the random number r_0 to the node 51A. FIG. 4 is a diagram schematically illustrating information transmitted from the node 50 to the node 51A. The node 51A stores the node ID ID # 0, the random number r_0, and the encrypted piece E (k_0) P in the data storage unit 517 in association with each other. Note that the data storage unit 517 stores each node ID string and each random number string in a state where the correspondence between the node ID and the random number generated by the node to which the node ID is assigned is held. In addition, each node ID included in the node ID string is held so that the transmission order of the nodes 50 and 51 that mediate transmission of the encrypted pieces can be determined. For example, in the node ID column, the node IDs are arranged in the order of the node 50 that transmitted first to the node that last transmitted.

  When the node 51A transmits an encrypted piece for the piece P in response to the piece request from the node 51B, the node 51A generates a random number r_1, generates a temporary symmetric key k_1 using this and the secret key s_1, Assume that the encrypted piece E (k_0) P is further encrypted using this and the encrypted piece E (k_1) E (k_0) P is output. E (k_1) E (k_0) P indicates that the piece P is encrypted with the temporary symmetric keys k_0 and k_1 in order. At this time, the node 51A is assigned to the node 51B and is stored in the unique information storage unit 510 in addition to the node ID ID # 0 stored in the data storage unit 517 and assigned to the node 50. In addition to the node ID ID # 1, the random number r_0 stored in the data storage unit 517, the random number r_1 generated by itself and the encrypted piece E (k_1) E (k_0) P are transmitted. FIG. 5 is a diagram schematically showing information transmitted from the node 51A to the node 51B. The node 51B stores the node ID string ID # 0, ID # 1, the random number string r_0, r_1, and the encrypted piece E (k_1) E (k_0) P in association with each other in the data storage unit 517.

  Next, a case where the node 51A does not perform encryption will be described. In this case, when the node 51A transmits an encrypted piece for the piece P in response to the piece request from the node 51B, an alternative random number is generated as described above as the random number r_1. In this case, the node 51A does not encrypt the piece P, and stores the unique information in addition to the node ID ID # 0 assigned to the node 50 stored in the data storage unit 517 for the node 51B. Node IDID # 1 assigned to itself, stored in unit 510, random number r_1 generated by itself in addition to random number r_0 stored in data storage unit 517, and encrypted piece E (k_0) P Send. FIG. 6 is a diagram schematically illustrating information transmitted from the node 51A to the node 51B. The node 51B associates the node ID string ID # 0, ID # 1, the random number string r_0, r_1, and the encrypted piece E (k_0) P and stores them in the data storage unit 517.

  In this way, the node 51 selectively performs further encryption on the encrypted piece by deciding whether or not to encrypt the encrypted piece according to a predetermined probability. Send the encrypted piece. At this time, the node 51 mediates the distribution of the encrypted piece, and mediates the distribution of the encrypted piece from the node 50 that is the distribution start node as the distribution path of the encrypted piece. The node ID sequence including the node IDs of the nodes 50 and 51 and the random number sequence including the random numbers generated by the nodes 50 and 51 are transmitted to the other nodes 51 together with the encrypted pieces.

  Returning to the description of FIG. The key request transmission unit 519 transmits a key request to the key server 53. The key request is information for requesting a decryption key for a piece, and includes key generation information for generating a decryption key, information for identifying content, and information for identifying a piece. It is a waste. Here, the key request transmission unit 519 requests a decryption key for decrypting the encrypted piece stored in the data storage unit 517, and also generates key generation information for generating the decryption key, and the encrypted piece. A key request including the associated content type ID and the piece number associated with the encrypted piece is transmitted to the key server 53. The key generation information is information used when generating an encryption key for a piece, and is information necessary for generating a decryption key for the piece. Here, the key generation information includes a node ID sequence and a random number sequence stored in the data storage unit 517 corresponding to the encrypted piece. The key request transmission unit 519 also transmits its own node ID to the key server 53 in order to identify its own node 51. The key server 53 may transmit the node ID included in the key request, or may transmit the node ID separately from the key request. Similarly, the content server ID and the piece number may be transmitted separately from the key request by the key server 53.

  For example, the node 51B receives a key request for requesting a decryption key for decrypting the encrypted piece E (k_1) E (k_0) P shown in FIG. 5 output when the node 51A performs encryption. When transmitting to the server 53, the key request transmission unit 519 of the node 51B generates a key request including the node ID string ID # 0, ID # 1, the random number string r_0, r_1, the content type IDCID, and the piece number m. Send. FIG. 7 is a diagram schematically showing information transmitted from the node 51B to the key server 53. As shown in FIG. Also, the node 51B sends a key request to the key server 53 for requesting a decryption key for decrypting the encrypted piece E (k_0) P shown in FIG. 6 output when the node 51A does not perform encryption. Also in the case of transmission, as shown in FIG. 7, the key request transmission unit 519 of the node 51B performs the node ID string ID # 0, ID # 1, the random number string r_0, r_1, the content type IDCID, and the piece number m. Send a key request containing As described above, when the node 51 requests the key server 53 for a decryption key for decrypting the encrypted piece, the node 51 indicates the distribution path of the encrypted piece, with the node 50 that is the distribution start node as a base point. A node ID string including the node IDs of the nodes 50 and 51 that mediate the distribution of the encrypted pieces, a random number sequence including the random numbers generated by the nodes 50 and 51, and the encrypted pieces are identified. The content type ID and the piece number are transmitted to the key server 53. At the time of these transmissions, the key request transmission unit 519 performs transmission while maintaining the correspondence between each node ID and the random number generated by the node to which each node ID is assigned.

  The piece decryption unit 520 receives the temporary symmetric key transmitted from the key server 53 in response to the key request transmitted from the key request transmission unit 519 as a decryption key, and decrypts the encrypted piece using the temporary symmetric key. For example, in the above-described example, when the node 51A performs encryption, the node 51B transmits the temporary request transmitted from the key server 53 in response to the key request including the node ID string and the random number string illustrated in FIG. Symmetric keys k_0 and k_1 are received. In other words, each decryption key for decrypting each encryption performed at least once on the piece is received. FIG. 8 is a diagram schematically showing information transmitted from the key server 53 to the node 51B. Piece P is decrypted with the temporary symmetric key shown in FIG. On the other hand, when the node 51A has not performed encryption, the node 51B receives the temporary symmetric key k_0 transmitted from the key server 53 in response to the key request including the node ID sequence and the random number sequence illustrated in FIG. Receive. FIG. 9 is a diagram schematically showing information transmitted from the key server 53 to the node 51B. In this way, the node 51 obtains a decryption key for decrypting each encryption according to the encryption selectively performed on the encrypted piece from the key server 53. Note that how the key server 53 generates the temporary symmetric key will be described later.

  Note that the order in which the node 51 obtains each of the plurality of pieces from which node and from which node is not particularly limited, but as described above, the node 51 encrypts each of the plurality of pieces. Each encrypted piece is acquired from the other nodes 50 and 51 by a piece request. Further, the node 51 receives each temporary symmetric key from the key server 53 by a key request for each encrypted piece, and obtains the distribution data described above by decrypting each encrypted piece.

<Key server configuration>
Next, various functions realized when the CPU of the key server 53 executes various programs stored in the storage device or the external storage device will be described. FIG. 10 is a diagram illustrating a functional configuration of the key server 53. The key server 53 includes a secret key storage unit 530, a data reception unit 531, an encryption skip determination unit 532, a temporary symmetric key generation unit 533, a data transmission unit 534, a piece information storage unit 535, and a distribution amount calculation. Unit 536, billing processing unit 537, reward point calculation unit 538, price information storage unit 539, reward point conversion information storage unit 540, and reward point storage unit 541. The secret key storage unit 530, the piece information storage unit 535, the price information storage unit 539, the reward point storage unit 541, and the reward point conversion information storage unit 540 are external storage such as an HDD of the key server 53, for example. This is reserved as a storage area in the apparatus. The substance of the data reception unit 531, the encryption skip determination unit 532, the temporary symmetric key generation unit 533, the data transmission unit 534, the charging processing unit 537, the delivery amount calculation unit 536, and the reward point calculation unit 538 is When the program of the CPU of the key server 53 is executed, it is generated on a storage device such as a RAM.

  The secret key storage unit 530 stores the secret key assigned to each node 50, 51 in association with the node ID assigned to each node 50, 51. The data receiving unit 531 requests a decryption key for decrypting the encrypted piece, and receives a key request including the above-described node ID sequence, random number sequence, content type ID, and piece number from the node 51. The data receiving unit 531 also receives from the node 51 the node ID of the node 51 itself that transmitted the key request.

The encryption skip determination unit 532 reads out the secret key stored in the secret key storage unit 530 in association with each node ID included in the node ID string included in the key request received by the data reception unit 531. Then, it is determined whether or not the following check expression is satisfied for each random number included in the random number sequence included in the key request. For example, each node ID included in the node ID column is ID # 0,..., ID # (j), and each node IDID # m (0 ≦ m ≦ j) corresponds to r_m and s_m, respectively. To do. In this case, the temporary symmetric key generation unit 533 determines whether or not the following check expression holds for all random numbers r_m (0 ≦ m ≦ j).
r_ m = F (s_m, ID # 0,…, ID # m) ... (inspection formula)

  In addition, when the node 51 generates a random number alternatively when distributing the encrypted piece, the above-described checking formula is established. That is, whether or not each random number is related to the encryption of the encrypted piece is determined by the check expression.

The temporary symmetric key generation unit 533 generates the decryption key k_m using the function F for all random numbers m for which the above-described check expression is not satisfied. This can be expressed by the following formula. The function F is the same as that used when the node 51 described above generates a temporary symmetric key. Therefore, here, the temporary symmetric key is restored by the function F using the temporary information and the secret key.
k_m = F (s_ m, r_ m)

  On the other hand, the node 51 that has generated a random number that satisfies the above check expression mediates the distribution of the encrypted piece, but does not perform encryption. For this reason, a decryption key is not generated for the random number.

  The data transmission unit 534 transmits the temporary symmetric key generated as the decryption key by the temporary symmetric key generation unit 533 to the node 51 that has transmitted the key request received by the data reception unit 531. For example, in the above example, when the node 51A performs encryption, the key server 53 is as shown in FIG. 8 in response to the key request including the node ID string and the random number string shown in FIG. Then, temporary symmetric keys k_0, k_1 are obtained for the random numbers r_0, r_1 and transmitted to the node 51B. Further, when the node 51A does not perform encryption, the key server 53 sets the random number r_0 as shown in FIG. 9 in response to the key request including the node ID sequence and the random number sequence shown in FIG. Only for this, a temporary symmetric key k_0 is obtained and transmitted to the node 51B. Thus, the number of temporary symmetric keys as a decryption key for decrypting an encrypted piece in which one piece is encrypted differs depending on the number of times of encryption performed selectively for the piece. This number may be one or plural. Each symmetric key for decrypting each encryption performed on the piece is transmitted to the node 51B, so that the node 51B can completely decrypt the encryption of the encrypted piece. .

  The price information storage unit 539 stores the price of each distribution data for each content type ID. FIG. 11 is a diagram illustrating the price of each distribution data stored in the price information storage unit 539. As shown in the figure, the content type ID and the price are stored in association with each other. The reward point storage unit 541 stores the total of reward points given by each node 51 performing secondary distribution for each node ID. This reward point is an incentive to secondary distribution. Specifically, the reward points are used for discounting from the amount charged when the node 51 to which the reward points are given transmits a key request to the key server 53 (referred to as a charge amount). FIG. 12 is a diagram illustrating the total of reward points stored in the reward point storage unit 541. As shown in the figure, the node ID and the total reward points are stored in association with each other. The piece information storage unit 535 stores piece information indicating the number of pieces of each piece of distribution data, the data size of each piece other than the last piece, and the data size of the last piece for each content type ID. FIG. 13 is a diagram illustrating piece information stored in the piece information storage unit 535. As shown in the figure, the content type ID and piece information are stored in association with each other. The reward point conversion information storage unit 540 stores reward points per unit amount (referred to as conversion points) for calculating reward points according to the distribution amount for each content type ID. FIG. 14 is a diagram illustrating conversion points stored in the reward point conversion information storage unit 540. Here, the unit amount is 1 kilobyte. As shown in the figure, the content type ID and the conversion point per kilobyte are stored in association with each other.

  Returning to the description of FIG. The charging processing unit 537 reads the reward points stored in the reward point storage unit 541 in association with the node ID of the node 51 that transmitted the key request, and the content type ID that is the same as the content type ID included in the key request. The price associated with and stored in the price information storage unit 539 is read, and the charge amount for the node 51 is calculated using the reward points and the price. Then, the charging processing unit 537 updates the reward points associated with the node ID and stored in the reward point storage unit 541 based on the value of the reward points used for calculating the charge amount.

  The distribution amount calculation unit 536 calculates the distribution amount of the piece for which the decryption key is requested by the key request. Specifically, the delivery amount calculation unit 536 reads the piece information stored in the piece information storage unit 535 in association with the content type ID included in the key request, and is assigned the piece number included in the key request. The distribution amount is calculated by determining the data size of the piece.

  The reward point calculation unit 538 calculates the reward points of the node 51 that has finally delivered the piece whose decryption key is requested by the key request, and updates the total of the reward points of the node 51. Specifically, the reward point calculation unit 538 first reads out the conversion points associated with the content type ID included in the key request and stored in the reward point conversion information storage unit 540, and this is read as the distribution amount calculation unit. Reward points are calculated by multiplying the distribution amount calculated by 536. For example, if the reward point is B, the conversion point is ρ, and the delivery amount is S, the reward point is calculated by the following equation 1.

  The reward point calculation unit 538 calculates the reward points stored in the reward point storage unit 541 in association with the node ID of the node 51 that transmitted the last in the node ID string included in the key request. The total reward points of the node 51 are calculated by adding the reward points. And the reward point calculation part 538 is memorize | stored in the reward point storage part 541 by replacing the reward point matched with the said node ID and memorize | stored in the reward point storage part 541 with the total of the calculated reward point. Update the total reward points you have. In this way, the reward point calculation unit 538 gives reward points to the other node 51 that has transmitted the last to the node 51 that has requested the key for a piece. If the reward point associated with the node ID has not yet been stored in the reward point storage unit 541, the reward point calculation unit 538 makes the decryption key requested for the piece requested by the key request. The calculated reward points are stored in the reward point storage unit 541 in association with the node ID of the node 51 that last distributed the piece.

  With the configuration as described above, the key server 53 performs a billing process for the piece for which the decryption key is requested in response to the key request from the node 51, and sends it to the other node 51 that last transmitted the piece. Reward point calculation processing is performed for calculating reward points according to the distribution amount corresponding to the data size of the piece. Then, the key server 53 performs a decryption key generation process for generating the decryption key, and transmits the decryption key to the node 51.

(2) Operation <Distribution start node: distribution processing>
Next, a procedure of processing performed in the data distribution system according to the present embodiment will be described. First, the procedure of the distribution process performed by the node 50 that is the distribution start node will be described with reference to FIG. The node 50 divides the distribution data into a plurality of pieces (step S1). When the node 50 receives a piece request for requesting a piece from another node 51 (step S2: YES), the node 50 generates a random number r_0 (step S3). Next, the node 50 generates a symmetric key k_0 by the function F using the random number r_0 and the secret key s_0 stored in the unique information storage unit 500 (step S4). Then, the node 50 encrypts the piece P to be transmitted using the symmetric key generated in step S4, and outputs the encrypted piece E (k_0) P (step S5). In addition, how to determine the piece to be transmitted is not particularly limited. Then, the node 50, for example, as shown in FIG. 4 with respect to the other node 51 that has transmitted the piece request received in step S2, node IDID # 0 stored in the unique information storage unit 500, The random number r_0 generated in step S4 and the encrypted piece E (k_0) P output in step S5 are transmitted (step S6). Thereafter, the process returns to step S2, and the node 50 waits for reception of a new piece request. Note that the piece requests received in step S2 are not necessarily the same node 51, and the pieces P requested by the piece requests are not necessarily the same piece. Further, the random number generated in step S3 basically differs for each process in step S3.

<Reception processing>
Next, a reception processing procedure in which the node 51 receives an encrypted piece from the node 50 or another node 51 will be described with reference to FIG. The node 51 transmits a piece request for requesting a piece to the node 50 or another node 51 (step S10). Next, the node 51 receives the node ID string, the random number string, and the encrypted piece from the node 50 or the other node 51 that is the partner that transmitted the piece request in step S10 (step S11). Then, the node 51 stores the node ID sequence, random number sequence, and encrypted piece received in step S11 in association with each other (step S12).

  When the node 51 transmits a piece request to the node 50, the node ID sequence, random number sequence, and encrypted piece shown in FIG. Here, although not shown in the figure, a node connected to the P2P network NT, where f is an integer equal to or greater than 1, will be generalized and described. For convenience of explanation, the node ID of the node is ID # f. The node to which the node ID ID # f is assigned is the node ID string ID # for the piece P as shown in FIG. 17 from the node to which the (f-1) th node IDID # (f-1) is assigned. 0, ..., ID # (f-1), random numbers r_0, ..., r_ {f-1} and encrypted pieces E (k_ {t}) ... E (k_0) P are received. However, t is an integer satisfying 1 ≦ t ≦ f−1. This means that the encrypted piece is not necessarily (f-1) times encrypted but the number of times of encryption. Depending on the node ID string ID # 0,..., ID # (f-1), it is specified by which node the encrypted piece was encrypted and transmitted, so that the delivery path of the encrypted piece is indicated. Become.

<Nodes other than the distribution start node: distribution processing>
Next, the procedure of the distribution process performed by the nodes 51 other than the distribution start node will be described with reference to FIG. When receiving a piece request for requesting a piece from another node 51 (step S20: YES), the node 51 determines whether or not to encrypt the encrypted piece to be transmitted according to a predetermined probability (step S21). . When the node 51 determines to encrypt the encrypted piece to be transmitted (step S21: YES), the node 51 generates a random number (step S22). Next, the node 51 generates a temporary symmetric key by the function F using the random number generated in step S22 and the secret key stored in the unique information storage unit 510 (step S23). The node 51 uses the temporary symmetric key generated in step S23 to further encrypt an encrypted piece that is an encrypted piece obtained by encrypting a piece P and is stored in the data storage unit 517, and newly The encrypted piece is output (step S24). Thereafter, the node 51 transmits the unique information in addition to the node ID stored in the data storage unit 517 in association with the encrypted piece to be transmitted to the other node 51 that has transmitted the piece request received in step S20. A new node ID sequence including the node ID stored in the storage unit 510 and a new random number including the random number generated in step S22 in addition to the random number sequence associated with the encrypted piece and stored in the data storage unit 517 The sequence and the new encrypted piece output in step S24 are transmitted (step S25).

  On the other hand, when the node 51 determines in step S21 that the encrypted piece to be transmitted is not encrypted (step S21: NO), the node string stored in the data storage unit 517 in association with the encrypted piece. Then, an alternative random number is generated by the function F using the secret key stored in the unique information storage unit 510 (step S26). After that, the node 51 does not perform the encryption performed in step S24, and is an encrypted piece to be transmitted to the other node 51 that has transmitted the piece request received in step S20, and the data storage unit 517. And a new node ID string including a node ID stored in the unique information storage unit 510 in addition to the node ID stored in the data storage unit 517 in association with the encrypted piece, In addition to the random number sequence associated with the encrypted piece and stored in the data storage unit 517, a new random number sequence including the alternative random number generated in step S26 is transmitted (step S27).

  For example, as shown in FIG. 19, the node assigned the node ID ID # f described above is assigned to the node P assigned the (f + 1) th node IDID # (f + 1) as shown in FIG. Node ID string ID # 0, ..., ID # (f-1), ID # f, random number string r_0, ..., r_f, and encrypted piece E (k_t ') ... E (k_0) P To do. However, t ′ is an integer of 1 ≦ t ′ ≦ f. This means that the encrypted piece has been encrypted not necessarily f times but less.

<Decryption process>
Next, the procedure of the decryption process in which the node 51 obtains the decryption key from the key server 53 and decrypts the encrypted piece using this will be described with reference to FIG. The node 51 reads the node ID sequence and random number sequence associated with the encrypted piece stored in the data storage unit 517 (Step S30), requests a decryption key for decrypting the encrypted piece, A key request including the node ID sequence and random number sequence, and the content type ID and piece number of the encrypted piece is transmitted to the key server 53 (step S31). At this time, the node 51 also transmits its own node ID to the key server 53. This node ID is used for billing processing. Next, the node 51 receives the temporary symmetric key transmitted from the key server 53 in response to the key request transmitted in step S30 as a decryption key (step S32), and decrypts the encrypted piece using the temporary symmetric key. (Step S33).

  For example, the node to which the above-described node ID ID # (f + 1) is assigned, with respect to the key server 53, as shown in FIG. 21, the node ID string ID # 0,..., ID # ( f-1), ID # f, random number sequence r_0,..., r_ {f-1}, r_f, content type IDCID, and piece number m are transmitted. Then, the node receives temporary symmetric keys k_0,..., K_t ′ for the piece P from the key server 53 as shown in FIG. 22, and uses them to encrypt the encrypted piece E (k_t ′). (k_0) P is decoded to obtain piece P. In this way, each node 51 can decrypt the encryption performed for the piece by obtaining all the temporary symmetric keys for decrypting the encryption performed for each piece, It becomes possible to completely decrypt the encrypted piece. In this way, each node 51 receives each temporary symmetric key from the key server 53 by a key request for each encrypted piece in which each of the plurality of pieces is encrypted, and decrypts each encrypted piece, The above distribution data can be obtained.

<Key server: Key transmission processing>
Next, a key transmission process procedure in which the key server 53 transmits a decryption key in response to a key request from the node 51 will be described with reference to FIG. Here, the key server 53 requests a decryption key for decrypting the encrypted piece, and sends a key request including a node ID sequence, a random number sequence, a content type ID and a piece number, and a node ID of the node 51 to the node If received from 51 (step S40: YES), first, a billing process is performed (step S41). Here, it is assumed that the key server 53 receives a key request for each piece and performs the subsequent processing for each piece. FIG. 24 is a flowchart showing the procedure of the charging process. The key server 53 reads the reward points stored in the reward point storage unit 541 in association with the node ID of the node 51 that transmitted the key request (step S60), and the same content as the content type ID included in the key request The price associated with the type ID and stored in the price information storage unit 539 is read (step S61). Then, the key server 53 sets the smaller value of the price and the reward point as a discount amount (step S62), and subtracts the discount amount from the price, thereby charging the node 51 with the charge amount. Is calculated (step S63). Thereafter, the key server 53 sets the value obtained by subtracting the discount amount from the reward point as a new reward point value for the node 51, and stores the reward points stored in the reward point storage unit 541 in association with the node ID. Is updated (step S64). If the reward point associated with the node ID of the node 51 is not stored in the reward point storage unit 541, the key server 53 performs the calculation with the value of the reward point set to “0”, and the charge amount Reward points are not updated after the calculation of.

  Returning to the description of FIG. After step S41, the key server 53 performs a reward point calculation process (step S42). FIG. 25 is a flowchart illustrating a procedure of reward point calculation processing. The key server 53 first reads the node ID included in the node ID string included in the key request (step S70), and determines whether or not the last transmitting node is the distribution start node (step S71). ). As described above, for example, when the node IDs are arranged according to the transmission order, the key server 53 determines whether or not the last node ID is the node ID of the distribution start node. If the node is a distribution start node (step S71: YES), the key server 53 ends the process. On the other hand, when the node is not a distribution start node (step S71: NO), the key server 53 reads piece information stored in the piece information storage unit 535 in association with the content type ID included in the key request (step S71). S72) The distribution amount is calculated by obtaining the data size of the piece to which the piece number included in the key request is assigned (step S73). For example, in the example of FIG. 13, when the content type ID is “12500012” and the piece number is “230”, the data size of the piece is “262144”, which is the distribution amount. Further, when the content type ID is “12500012” and the piece number is “2351”, the data size of the piece is “143”, which is the distribution amount.

  Next, the key server 53 reads the conversion points associated with the content type ID included in the key request and stored in the reward point conversion information storage unit 540, and multiplies this with the distribution amount calculated in step S73. The reward points are calculated (step S74). Then, the key server 53 assigns the reward point stored in the reward point storage unit 541 in association with the node ID of the node 51 that has transmitted last, that is, the node ID referenced in step S70, to step S74. The total reward points of the node 51 are calculated by adding the reward points calculated in (1). And the key server 53 is memorize | stored in the reward point storage part 541 by replacing the total of the calculated reward point, and the sum of the reward point matched with the said node ID, and memorize | stored in the reward point storage part 541. The total of reward points being updated is updated (step S75). If the reward point associated with the node ID is not yet stored in the reward point storage unit 541, the key server 53 distributes the reward point calculated in step S74 at the end of the piece. The reward point storage unit 541 stores the node ID in association with the node ID of the node 51.

  Returning to the description of FIG. After step S42, the key server 53 performs a decryption key generation process (step S43). FIG. 26 is a flowchart showing the procedure of the decryption key generation process. The key server 53 reads, for each node ID, the secret key stored in the secret key storage unit 530 in association with each node ID included in the node ID string included in the key request received in step S40 (step S80). ). Then, the key server 53 determines, for each of all random numbers included in the random number sequence, whether or not the above-described check expression is established by the function F using the random number and the secret key corresponding to the random number. (Step S81). Then, the key server 53 generates a temporary symmetric key as a decryption key by the function F for each node ID using the random numbers for all the node IDs for which the check expression is not satisfied and the secret key read in step S80 (step S82). .

  Returning to the description of FIG. After step S43, the key server 53 transmits the temporary symmetric key generated as the decryption key in step S82 to the node 51 that transmitted the key request received in step S40 (step S44).

  For example, the key server 53 has a node ID sequence and a random number sequence as shown in FIG. 21, a content type ID and a piece for the piece P with respect to the node to which the node ID ID # (f + 1) is assigned. In response to a key request including a number, temporary symmetric keys k_0,..., K_t ′ as shown in FIG.

  As described above, in the data distribution system in which each node performs encryption using a unique encryption key for each piece and distributes it via the P2P network NT, decryption for decrypting each piece Using the information used for key generation, an incentive is given to the node 51 responsible for secondary distribution according to the distribution amount. In other words, the decryption key is generated using the random number sequence and the node ID sequence included in the key request, the node 51 that has transmitted the last is specified, and the content type ID and the piece number are used to determine the node 51 By calculating the distribution amount and calculating the reward points for the node 51, an incentive corresponding to the correct distribution amount is given to the node to be given. In this way, the node that has performed the secondary distribution does not notify the distribution amount, but uses information transmitted when the node that has received the secondary distribution requests the key server 53 for a decryption key. By providing the key server 53 with an incentive, it is possible to prevent an amount of distribution from being illegally notified or a node that is not actually in charge of secondary distribution from acquiring an incentive illegally. For example, when a certain node 51 transmits to the key server 53 a key request including a node ID string in which the node ID of the node that last transmitted a certain piece is false, the key server 53 is correct using the node ID. Since a decryption key cannot be generated, the certain node 51 cannot decrypt the piece. For this reason, by using information that cannot be falsified in order to decrypt pieces for granting incentives, it is possible to correctly grant incentives and prevent fraud.

  Further, by providing reward points used for discounting in the billing process as an incentive, secondary distribution can be effectively encouraged. In addition, since an incentive according to the amount of distribution can be given, it is possible to increase the number of nodes that remain connected to the P2P network even after receiving a node or piece having a large uplink capacity. In particular, it is possible to increase the number of nodes having a larger distribution amount than the reception amount. As a result, even if the distribution amount increases, it can be expected that the distribution cost of the distribution data provider is reduced.

[Second Embodiment]
Next, a second embodiment of the server, the information processing method, and the program will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

(1) Configuration In the first embodiment described above, reward points are given as incentives only to the node 51 that has transmitted the last, other than the distribution start node. In the present embodiment, reward points are given not only to the node 51 that transmitted the last but also to each node 51 that mediates transmission other than the distribution start node.

  The configuration of the key server 53 according to the present embodiment differs from the configuration of the key server 53 according to the first embodiment described above in the following points. The reward point calculation unit 538 first calculates converted points stored in the reward point conversion information storage unit 540 in association with the content type ID included in the key request in the same manner as in the first embodiment described above. Reward points are calculated by multiplying this by the distribution amount calculated by the distribution amount calculation unit 536. Then, the reward point calculation unit 538 adds each calculated reward point to each reward point stored in the reward point storage unit 541 in association with each node ID included in the node ID included in the key request. The total of reward points of each node 51 is calculated. Then, the reward point calculation unit 538 replaces the reward points associated with each node ID and stored in the reward point storage unit 541 with the total of the calculated reward points. Each of the stored reward points is updated. When the reward point associated with the node ID is not yet stored in the reward point storage unit 541, the reward point calculation unit 538 calculates the decryption key requested for the piece by the key request. The reward points are stored in the reward point storage unit 541 in association with the node ID. Other configurations are the same as those in the first embodiment.

(2) Operation Next, a procedure of reward point calculation processing performed when the key server 53 according to the present embodiment performs the above-described key transmission processing will be described with reference to FIG. Other processing procedures are the same as those in the first embodiment. The key server 53 first performs steps S70 to S74 in the same manner as in the first embodiment described above, and calculates reward points according to the distribution amount of pieces for which a decryption key is requested by a key request. Thereafter, in step S75 ′, the key server 53 is a node ID included in the node ID string and is associated with the node ID of the node 51 other than the distribution start node and stored in the reward point storage unit 541. The total reward points of each node 51 are calculated by adding the reward points calculated in step S74 to the points. Then, the key server 53 replaces each reward point associated with each node ID and stored in the reward point storage unit 541 with the total of the calculated reward points, thereby causing the reward point storage unit 541 to respectively Each of the stored reward points is updated. For node IDs whose reward points are not yet stored in the reward point storage unit 541, the key server 53 causes the reward point storage unit 541 to store the reward points calculated in step S74 in association with the node ID. . As described above, the key server 53 grants reward points to each node 51 that mediates transmission of pieces other than the distribution start node.

  As described above, secondary distribution is also possible by giving reward points according to the distribution amount to each node 51 that mediates transmission, not just the node 51 that performed the transmission at the end other than the distribution start node. Can be effectively encouraged.

[Third embodiment]
Next, a second embodiment of the server, the information processing method, and the program will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment or 2nd Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

(1) Configuration In the above-described second embodiment, for certain distribution data, reward points to be given to each node 51 that mediates transmission other than the distribution start node are all the same if the distribution amount is the same. It was said that. In the present embodiment, the key server 53 determines not only the distribution amount but also the profit distribution rate for each node 51 according to the transmission order and the piece number, and reward points according to the profit distribution rate. Is assigned to each.

  The configuration of the key server 53 according to the present embodiment differs from the configuration of the key server 53 according to the first embodiment described above in the following points. The reward point conversion information storage unit 540 calculates a reward point (converted point) per unit amount for calculating a reward point according to the distribution amount and a weighting factor for determining a profit distribution rate for each content type ID. Remember. FIG. 28 is a diagram illustrating conversion points and weighting factors stored in the reward point conversion information storage unit 540. Here, the unit amount is kilobytes. As shown in the figure, the content type ID, the conversion point per kilobyte, the weight function, and the index specifying the weight of the weight function are stored in association with each other. The arguments of this weight function are the transmission order of each node 51 and the piece number. The transmission order of each node 51 corresponds to the parameter i.

  The reward point calculation unit 538 reads the conversion point, the weight function Φr, and the indices r and t stored in the reward point conversion information storage unit 540 in association with the content type ID included in the key request, and the key request The piece information stored in the piece information storage unit 535 in association with the content type ID included in is read out and the number M of pieces is acquired. Furthermore, the reward point calculation unit 538 acquires the number of times that transmission has been mediated, that is, the number N of node IDs included in the node ID string included in the key request. Then, the reward point calculation unit 538 sets a parameter i and a piece number m for giving reward points to each node ID included in the node ID string included in the key request as arguments of the weight function. The value of the parameter i corresponds to the transmission order of the nodes 50 and 51 that mediate transmission. Then, the reward point calculation unit 538 calculates, for each parameter i, the weight for the node 51 that is included in the node ID string and to which the node ID in the transmission order corresponding to the parameter i is assigned. This weight corresponds to the profit distribution rate. Accordingly, the weight function Φr and the indices r and t are set so that the weight function Φr, the indices r and t, the number of pieces M, the number N of node IDs, the parameter i and the piece number m satisfy the following formula 2. Although it is desirable to do, it is not restricted to this. When the key server 53 receives the key request shown in FIG. 21, “N = f + 1”.

  Then, the reward point calculation unit 538 uses the calculated weight, the distribution amount calculated by the distribution amount calculation unit 536, and the conversion point, for the node 51 to which the node ID of the transmission order corresponding to the parameter i is assigned. Reward points are calculated for each parameter i, for example, using Equation 3 below. The reward point is B, the delivery amount is S, and the conversion point is ρ.

  Then, the reward point calculation unit 538 adds the calculated reward points to each of the reward points associated with the node ID of the node 51 and stored in the reward point storage unit 541, so that the reward points of each node 51 The total of each is calculated. Then, the reward point calculation unit 538 replaces the total of the reward points associated with each node ID and stored in the reward point storage unit 541 with the calculated total of reward points. Each of the total reward points stored in 541 is updated. For node IDs whose reward points are not yet stored in the reward point storage unit 541, the reward point calculation unit 538 calculates the reward points calculated for the piece for which the decryption key is requested by the key request. The reward point storage unit 541 stores it in association with the ID. Other configurations are the same as those of the first embodiment or the second embodiment.

(2) Operation Next, a procedure of reward point calculation processing performed when the key server 53 according to the present embodiment performs the above-described key transmission processing will be described with reference to FIG. Other processing procedures are the same as those in the first or second embodiment described above. First, the key server 53 reads each node ID included in the node ID string included in the key request (step S80), and sets a parameter i for giving reward points to each node ID (step S81). ). In the example of the key request in FIG. 22, the key server 53 first sets “i = f”. Then, the key server 53 refers to the node ID of the transmission order included in the node ID string and corresponds to the parameter i, and determines whether or not the node to which the node ID is assigned is the distribution start node (step) S82). If the node is a distribution start node (step S82: YES), the key server 53 ends the process. If the node is not a distribution start node (step S82: NO), the key server 53 performs steps S71 to S72 similar to those in the first embodiment described above, and the piece of the piece for which the decryption key is requested by the key request. Calculate delivery volume. Next, the key server 53 reads the conversion point, the weight function Φr, and the indices r and t stored in the reward point conversion information storage unit 540 in association with the content type ID included in the key request, and the key request The piece information stored in the piece information storage unit 535 associated with the content type ID included in the piece information is read out to obtain the number M of pieces, and the number N of each node ID included in the node ID column included in the key request is obtained. Obtain (step S83). Then, the key server 53 uses the number of pieces M and the number N of node IDs as indices of the weight function Φr. Next, the key server 53 sets the parameter i and the piece number m in the argument of the weight function read in step S83, and calculates the weight for the node 51 (step S84).

  Then, the key server 53 calculates the weight calculated in step S84, the distribution amount calculated in step S72, the conversion point read in step S83, the weight function Φr and the indices r and t read in step S83, and the index. Using the number M of pieces and the number N of node IDs set as numbers, the reward points for the node 51 to which the node IDs in the order corresponding to the parameter i are assigned are calculated (step S85). And the key server 53 memorize | stores in the reward point storage part 541 by replacing the reward point matched with the said node ID and memorize | stored in the reward point storage part 541 with the total of the reward point calculated at step S85. The total of the reward points being updated is updated (step S86). For node IDs whose reward points are not yet stored in the reward point storage unit 541, the key server 53 stores the reward points calculated in step S85 in the reward point storage unit 541 in association with the node IDs. . Thereafter, the key server 53 resets the parameter i as 'i = i-1' (step S87), refers to the node ID of the transmission order corresponding to the parameter i, and is assigned to the node ID of the node Is a distribution start node (step S88). Until it is determined that the node to which the node ID of the transmission order corresponding to the parameter i is assigned is the distribution start node (step S88: YES), the key server 53 repeats the processes of steps S84 to S87. That is, in the example of the key request of FIG. 22, the key server 53 repeats the processing of steps S84 to S87 until the value of the parameter i changes from “f” to “1”, and transmits the pieces other than the distribution start node. The profit distribution rate is determined according to the transmission order and the piece number, and reward points according to the profit distribution rate and the distribution amount are assigned to each node 51 that mediates the above.

  As described above, it is possible to effectively and flexibly encourage secondary distribution by giving each node 51 reward points according to the distribution amount, transmission order, and piece number.

  In the above example, the parameter i corresponding to the transmission order and the piece number m are set as arguments of the weighting factor, but the argument of the weighting factor is not limited thereto. Further, as the indices of the weighting coefficients, predetermined indices r and t, the number of pieces M, and the number N of node IDs are used, but the indices are not limited to these.

(3) Example of Weight Function Here, an example of the weight function will be described. For example, as in the first embodiment described above, the weight function when reward points are given only to the node 51 that has transmitted the last is represented by, for example, the following Expression 4.

  Similarly to the above-described second embodiment, a weighting function in the case where reward points are equally assigned to each node 51 that mediates transmission of a piece is represented by, for example, the following Expression 5.

  Also, the weighting function for giving reward points so that the earlier the transmission order is, the smaller the value of parameter i is, and the larger the transmission order is, the slower the transmission order is (here, the larger the value of parameter i) is, For example, it is represented by the following formula 6.

  Moreover, it is a case where reward points are given only to the node 51 that sent the last, and the smaller the piece is, the smaller the piece is (the smaller the piece number is here), and the closer the piece is to the tail (here, For example, the weighting function in the case of giving reward points so as to be larger (as the piece number is larger) is expressed by the following Expression 7.

  Also, the earlier the transmission order is, the smaller the transmission order is, and the larger the piece is, the closer the piece is to the beginning (the smaller the piece number is here), and the smaller the piece is, the closer the piece is to the end (here, the larger the piece number is). For example, the weighting function in the case of giving reward points is expressed by the following Expression 8. Expression 8 is obtained by multiplying the right side and the left side of Expression 6.

  For example, by calculating the reward points so that the closer the piece is to the end, even if the amount of delivery is the same, the reward points of Equations 7 and 8 are calculated so that the second piece of the last piece that is difficult to be distributed secondarily. The next delivery can be encouraged more effectively.

In addition, each node 51 calculates a delivery amount for each delivery data that has been subjected to secondary delivery, and uses each delivery amount, a conversion point per unit amount, and a weighting factor according to the transmission order to each node. Reward points to be given to 51 may be calculated. The calculation formula for calculating the reward points in this case is expressed by, for example, the following formula 9. Note that D _i is the distribution amount that the node 51 to which the node ID in the transmission order corresponding to the parameter i is assigned transmits the distribution data. C is a conversion point per unit amount of distribution data, and is a value calculated by a constant or a function. N is the number of times the transmission has been mediated, and w _{i, N} is a weighting factor for the node 51 to which the node ID of the transmission order corresponding to the parameter i is assigned. The weight coefficient w _{i, N} preferably satisfies the following expression 10, but is not limited thereto.

Specific calculation formulas for calculating the weighting coefficients w _{i, N} are expressed by, for example, Expressions 11 to 13. According to Equation 11, the weight of each node 51 that has performed the secondary distribution is equally divided.

  R in Equation 12 is a proportionality coefficient, and is a constant “0 <r <1”. According to Equation 12, the weight of each node 51 is smaller as the transmission order is earlier and larger as the transmission order is later.

  R in Equation 13 is a proportionality coefficient and is a constant such that ‘0 <r <1/2’. According to Equation 13, the weight of each node 51 is smaller as the transmission order is earlier and smaller as the transmission order is later, but the node 51 to which the node ID of the transmission order corresponding to the parameter i of i = 1 ′ is assigned. That is, the weight of the node 51 that directly receives the distribution data from the node 50 that is the distribution start node is exceptionally large.

[Modification]
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined. Further, various modifications as exemplified below are possible.

<Modification 1>
In the above-described embodiment, various programs executed in each node 50 may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. In addition, the program is recorded in a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disk) in a file in an installable or executable format. You may comprise so that it may provide. In this case, the program is loaded onto the main storage device (for example, RAM) by being read from the recording medium at each node 50 and executed, and each unit described in the functional configuration is generated on the main storage device. The The same applies to various programs executed by the key server 53.

  In the above-described embodiment, all or a part of the units described in the functional configuration of each node 50 may be configured by hardware. The same applies to all or some of the components described in the functional configuration of the key server 53.

<Modification 2>
In the above-described embodiment, the device identification information is a node ID. However, the present invention is not limited to this, and any information that can uniquely identify each node may be used. For example, the IP address or MAC address of each node Or a URL.

  In the above-described embodiment, the piece specifying information is the piece number assigned in order from the top of the content. However, any piece of information may be used as long as it is information for identifying the piece. It may be the number of bytes from the beginning or a hash value of a piece.

<Modification 3>
In the data distribution system of the embodiment described above, the number of distribution start nodes may be plural. Further, the number of other nodes connected to the P2P network NT is not particularly limited.

  In the embodiment described above, the key server 53 may be physically the same device as the other nodes 50 and 51 such as the distribution start node.

  In the above-described embodiment, the key server 53 performs processing in the order of charging processing, reward point calculation processing, and decryption key generation processing, but the processing order is not limited to this order.

  In the above-described embodiment, the key server 53 includes the billing processing unit 537, the piece information storage unit 535, the delivery amount calculation unit 536, the price information storage unit 539, the reward point calculation unit 538, the reward A point storage unit 541 and a reward point conversion information storage unit 540 are provided. However, the key server 53 may not include these units, but a server including these units may be separately provided in the data distribution system, and the server and the key server 53 may be connected. In such a configuration, the key server 53 includes all or part of the node IDs included in the node ID sequence included in the key request, the random number sequence, the content type ID and the piece number, and the node 51 that has transmitted the key request. Are sent to the server. The server that has received these may perform billing processing and reward point calculation processing in the same manner as the key server 53 described above. The server is not configured as a single device, but is configured by a plurality of devices, for example, a server including at least a charging processing unit 537 and a server including at least a delivery amount calculation unit 536 and a reward point calculation unit 538. You may do it.

<Modification 4>
In the above-described embodiment, a plurality of pieces may be requested by one piece request. In this case, the nodes 50 and 51 may transmit the pair of the encrypted piece, the node ID sequence, and the random number sequence to the other nodes 51 that transmitted the piece request as described above for each of the plurality of pieces.

  In the above-described embodiment, the nodes 50 and 51 are configured to transmit the encrypted piece in response to the piece request. However, the present invention is not limited to this, and the other nodes 51 may receive the piece request without receiving the piece request. The node ID sequence and the random number sequence may be transmitted together with the encrypted piece.

<Modification 5>
In the above-described embodiment, the node 51 sends a key request for decrypting each encrypted piece when the encrypted pieces are acquired and stored in the data storage unit 517 for all pieces constituting the distribution data. You may make it transmit to the key server 53. FIG. In this case, the node 51 may not transmit the piece number to the key server 53. Alternatively, the node 51 sends a key request for decrypting the encrypted piece stored in the data storage unit 517 to the key server even if the encrypted pieces are not acquired for all pieces constituting the distribution data. You may make it transmit to 53. Further, the node 51 may request a decryption key for decrypting one encrypted piece by one key request, or request each decryption key for decrypting a plurality of encrypted pieces. You may do it.

  Note that the node 51 may perform decoding after receiving all the pieces, or may perform it every time a piece is received. In addition, when the distribution data is image data or music data and the distribution data is decoded and reproduced, the node 51 may reproduce all pieces or only some pieces. However, you may reproduce | regenerate for every piece.

<Modification 6>
In the above-described embodiment, each time the nodes 50 and 51 transmit the encrypted pieces stored in the data storage unit 517 to the other nodes 51, a random number is generated. However, the nodes 50 and 51 may generate random numbers according to the number of times of transmission of encrypted pieces, for example, instead of generating random numbers each time. For example, the nodes 50 and 51 may generate a new random number every time the encrypted piece is transmitted a predetermined number of times (for example, 5 times). The timing at which the nodes 50 and 51 generate random numbers may be when a piece request is received from another node 51, or may be every predetermined time.

  Further, in the above-described embodiment, when the node 51 encrypts the encrypted piece stored in the data storage unit 517 and transmits the encrypted piece to the other node 51, a part of the encrypted piece of data is not the whole. The data may be encrypted. In this case, the data encrypted by each node 51 that mediates the distribution of the encrypted piece is overlapped with the data encrypted by the other node 51 that also mediates the distribution of the encrypted piece. The node 51 may encrypt part of the data of the encrypted piece. According to such a configuration, it is possible to reduce the processing load related to encryption performed by each node 51, and it is possible to suppress the influence when the decryption key is exposed by duplicating the encrypted part. become.

<Modification 7>
In the above-described embodiment, the node ID sequence and the random number sequence that the node 51 transmits to the other nodes 51 together with the encrypted pieces are, for example, (ID # 0, r_0), (ID # 1, r_1). As in (#f, r_f), etc., a form in which a set of a node ID and a random number corresponding to the node ID is shown for each node ID may be used.

<Modification 8>
In the above-described embodiment, the piece symmetric key is a temporary symmetric key that is both an encryption key and a decryption key for decrypting the encryption. However, the encryption key used for encrypting the piece may be different from the decryption key for decrypting the encryption performed on the encrypted piece.

  In each of the above-described embodiments, each of the nodes 50 and 51 generates a temporary symmetric key used for piece encryption using a random number and a secret key. Alternatively, the random number itself may be used as a temporary symmetric key, or a temporary symmetric key may be generated using a random number and a piece number.

  In the above-described embodiment, the secret key is used as the secret information uniquely assigned to each of the nodes 50 and 51. However, the present invention is not limited to this.

  In the above embodiment, the secret key is uniquely assigned to each of the nodes 50 and 51. However, the present invention is not limited to this. For example, the same secret key may be assigned to some of the nodes 50 and 51.

  In the above-described embodiment, the method for sharing the secret information between the nodes 50 and 51 and the key server 53 is not limited. For example, the secret information may be encrypted in advance using a public key or a method for sharing the secret information. A method of simultaneously distributing secret information to the node 51 and the key server 53 at the time of piece distribution may be used. Further, the secret information may not be shared between the nodes 50 and 51 and the key server 53, but the secret information may not be shared using an asymmetric key.

<Modification 9>
In the above-described embodiment, the above-described encrypted piece, node ID string, and random number string may be distributed in the form of package data. In this case, the package data may be recorded on a computer-readable recording medium and provided to the node, or may be configured to be downloaded to the node via the server. In response to the piece request, the node that has acquired the package data, in the same manner as in the above-described embodiment, an encrypted piece that is selectively encrypted with respect to the encrypted piece included in the package data; The node ID included in the package data and its own node ID, the random number sequence included in the package data, and the random number generated by itself may be transmitted to other nodes.

<Modification 10>
In the above-described embodiment, the node 50 that is the distribution start node may selectively perform encryption according to a predetermined probability in the same manner as the node 51 when transmitting the encrypted piece. In this case, the node 50 may be configured to have the same functions as the encryption determination unit 521 and the random number alternative generation unit 522 included in the node 51 described above.

  In the above-described embodiment, the probability that the node 51 selectively performs encryption is predetermined, but this may be variable. For example, the probability may be changed according to the number of times the distribution of the encrypted piece is mediated (referred to as the number of vias), or a fixed value and a variable value may be used properly.

<Modification 11>
Data distribution system for determining whether to encrypt key server 53 according to each embodiment described above when each node 51 transmits a piece, encrypting the piece according to the determination result, and transmitting the piece However, the present invention is not limited to this, and the present invention may be applied to a data distribution system that performs encryption every time each node 51 transmits a piece.

  In addition, each node 51 does not transmit the encrypted data with respect to the piece in this way, but each node 51 receives the encrypted piece from the other nodes 50 and 51 and further decrypts the encrypted piece. The decryption key is received, the encrypted piece is once decrypted using the decryption key, the decrypted piece is newly encrypted, a new encrypted piece is output, and the new encrypted piece is You may apply to the data delivery system which transmits to the other node 51. FIG. In this case, each node 51 may receive the decryption key from the key server 53, or may receive it from the node 51 itself that has encrypted the piece. Further, the decryption key itself may be transmitted after being encrypted.

<Modification 12>
In each embodiment described above, reward points are set variably for each distribution data, and the key server 53 is provided with a reward point storage unit 541 for storing reward points for each distribution data. Not limited to this, the same reward point may be set for all distribution data. In this case, the key server 53 may not include the reward point storage unit 541, and the node 51 may not include the content type ID when transmitting the key request to the key server 53.

  In each of the above-described embodiments, the piece information storage unit 535 stores the data size separately from the other pieces for the last piece, and calculates the delivery amount using this data size. However, the delivery amount may be calculated for the last piece using the same data size as the other pieces.

  When the data size of each piece of each piece of distribution data is fixed and all the same, the key server 53 does not include the piece information storage unit 535, and the node 51 transmits the key request to the key server 53 when the content is transmitted. The type ID may not be included.

<Modification 13>
In each of the above-described embodiments, the key server 53 performs the billing process every time a key request is received. However, the present invention is not limited to this. For example, the key server 53 may perform the billing process only when the piece number included in the key request is a specific value.

  Further, in each of the above-described embodiments, the price information storage unit 539 stores not only the price of each distribution data, but also exchange points that are values of reward points that can be exchanged as points equivalent to the price. Also good. FIG. 30 is a diagram exemplifying prices and exchange points stored in the price information storage unit 539 according to the present modification. As shown in the figure, the content type ID, the price of the distribution data, and the exchange point are stored in association with each other. For example, the distribution data whose content type ID is “12500013” is equivalent to a reward point of 1000 points, and can be exchanged for the exchange point with this point as an exchange point. In such a configuration, the billing processing unit 537 calculates a billing amount for the node 51 that transmitted the key request, using the reward points, the price, and the exchange points.

  FIG. 31 is a flowchart showing the procedure of the billing process according to this modification. The key server 53 reads the reward points stored in the reward point storage unit 541 in association with the node ID of the node 51 that transmitted the key request (step S60), and the same content as the content type ID included in the key request The price and exchange point associated with the type ID and stored in the price information storage unit 539 are read (step S61 ′). Then, the key server 53 determines whether or not the exchange point is equal to or less than the reward point (step S65). When the exchange point is equal to or less than the reward point (step S65: YES), the exchange point is subtracted from the reward point. Using the value as the value of the new reward point, the reward point associated with the node ID and stored in the reward point storage unit 541 is updated (step S66), and the accounting process is terminated. On the other hand, when the exchange point is larger than the reward point (step S65: NO), the key server 53 performs the processes of steps S62 to S64 in the same manner as in the first embodiment described above.

  Even with the configuration as described above, the incentive can be correctly given to the node 51 responsible for the secondary distribution according to the distribution amount.

<Modification 14>
In each of the above-described embodiments, the reward points to be given as incentives are used for discounting in the subsequent billing process. However, the present invention is not limited to this. For example, the reward points can be exchanged for bonus benefits. May be. In this case, for example, the key server 53 may include a providing unit that provides a privilege to the node 51 that has transmitted the key request according to the reward points given to the node 51. Or you may make it provide separately the server provided with such a provision part in a data delivery system.

  Note that the key server 53 may determine whether to use the reward points as a discount or to exchange them for a privilege, and perform the charging process according to the determination result. FIG. 32 is a flowchart illustrating a procedure of key transmission processing according to the present modification. After step S40, in step S100, the key server 53 determines whether the piece for which the decryption key is requested by the key request is charged or free, or whether reward points are used in exchange for a privilege. In addition, what is necessary is just to make it memorize | store in advance in the key server 53 in association with the piece number of each piece, for example whether each piece is paid or free, or a reward point is used by exchange with a privilege. And when the said piece is free, the key server 53 performs the process of step S42-S44 similar to each above-mentioned embodiment. On the other hand, when the piece is charged or the reward points are used by exchanging with a privilege, the billing process in step S41 similar to each of the above embodiments is performed, and then it is determined whether billing is possible ( Step S101). When charging is possible (step S101: YES), the key server 53 performs the processing of steps S42 to S44, and when charging is not possible (step S101: NO), it indicates that the decryption key cannot be transmitted. The message is transmitted to the node 51 that transmitted the key request (step S102).

  An expiration date may be set for the reward points. FIG. 33 is a diagram illustrating reward points stored in the reward point storage unit 541 according to the present modification. As shown in the figure, the expiration date is stored in association with the reward points for each node. In such a configuration, when the key server 53 performs the charging process, if the expiration date associated with the reward point stored in the reward point storage unit 541 has not elapsed from the current date and time, the reward point If the expiration date has passed from the current date and time, the value of the reward point is set to “0” and the charging process may be performed.

<Modification 15>
In each of the above-described embodiments, the conversion point is variably set for each distribution data, and the key server 53 includes the reward point conversion information storage unit 540 that stores the conversion points for each distribution data. Not limited to this, the same conversion point may be set for all distribution data. In this case, the key server 53 may not include the reward point conversion information storage unit 540, and the node 51 may not include the content type ID when transmitting the key request to the key server 53.

<Modification 16>
In each embodiment described above, the reward point is not given to the node 51 that is the distribution start node, but the reward point may be given.

50, 51, 51A, 51B Node 53 Key server 500 Unique information storage unit 501 Random number generation unit 502 Temporary symmetric key generation unit 503 Piece encryption unit 504 Piece generation unit 505 Data transmission unit 506 Transmission request reception unit 510 Unique information storage unit 511 Random number generator 512 Temporary symmetric key generator 513 Piece encryption unit 514 Data reception unit 515 Data transmission unit 516 Transmission request reception unit 517 Data storage unit 518 Transmission request transmission unit 519 Key request transmission unit 520 Piece decryption unit 521 Encryption determination unit 522 Random number alternative generation unit 530 Private key storage unit 531 Data reception unit 532 Encryption skip determination unit 533 Temporary symmetric key generation unit 534 Data transmission unit 535 Piece information storage unit 536 Delivery amount calculation unit 537 Charge processing unit 538 Reward point calculation unit 539 Price information storage unit 540 Information storage unit 541 reward point storage unit NT P2P networks

Claims (16)

The piece is a part of data, which is encrypted by the communication device and transmitted from the communication device to the other communication device,
The key request for requesting a decryption key for decrypting the piece includes data identification information for identifying the data and key generation information for generating the decryption key, and the other Transmitted from the communication device,
The key generation information includes device identification information assigned to the communication device,
Obtaining means for obtaining the data identification information and the key generation information included in the key request;
First calculation means for calculating a delivery amount, which is a data amount of the piece transmitted by the communication device, using the data identification information and the key generation information;
Second calculation means for calculating reward points to be given to the communication device using the delivery amount;
A server comprising: first storage means for storing the reward points in association with the device identification information. The key request further includes piece specifying information for specifying the piece,
The acquisition means further acquires the piece identification information,
2. The server according to claim 1, wherein the first calculation unit calculates the distribution amount also using the piece specifying information. The pieces are encrypted with different encryption keys by all or part of a plurality of communication devices that mediate transmission,
The key generation information is information for generating one or a plurality of decryption keys for decrypting the piece, and each of the devices can determine the transmission order of the plurality of communication devices that mediate the transmission of the pieces. Including identification information,
The acquisition means acquires the data identification information and the device identification information of the communication device that last transmitted the piece,
The second calculation means calculates a reward point to be given to another communication device that has transmitted the piece last, using the distribution amount,
The server according to claim 1, wherein the first storage unit stores the reward points in association with the device identification information of a communication device that has transmitted the piece last. The piece is encrypted by the first communication device that mediates transmission using the first encryption key, transmitted to the second communication device, and then decrypted by the second communication device using the second encryption key. Is encrypted,
The key generation information is information for generating a decryption key for decrypting the piece encrypted using the second encryption key, and includes the device identification information of the second communication device,
The acquisition means acquires the data identification information and the device identification information of the second communication device,
The second calculation means calculates a reward point to be given to the second communication device using the distribution amount,
The server according to claim 1, wherein the first storage unit stores the reward points in association with the device identification information of the second communication device. The pieces are each encrypted by all or part of a plurality of communication devices that mediate transmission,
The key generation information is information for generating one or a plurality of decryption keys for decrypting the piece, and includes the device identification information of the plurality of communication devices that mediate transmission of the piece. ,
The acquisition means acquires the data identification information and the device identification information of each of the communication devices,
The second calculation means calculates reward points to be given to the communication devices that mediate transmission of the pieces, using the distribution amount,
The server according to claim 1, wherein the first storage unit stores the reward points in association with the device identification information of each of the communication devices. The pieces are each encrypted by all or part of a plurality of communication devices that mediate transmission,
The key generation information is information for generating one or a plurality of decryption keys for decrypting the piece, and the transmission order of the plurality of communication devices that mediate transmission of the pieces can be determined. Device identification information,
The acquisition means acquires the data identification information and the device identification information of each of the communication devices,
The second calculation means calculates the reward points according to the transmission order for the communication devices that mediate the transmission of the pieces using the distribution amount,
The server according to claim 1, wherein the first storage unit stores the reward points in association with the device identification information of each of the communication devices. The piece specifying information specifies which part of the data the piece is,
A second storage means for storing size information indicating the data amount of the piece according to which part of the data;
The said 1st calculation means calculates the said delivery amount by discriminating the data amount of the said piece using the said data identification information, the said piece specific information, and the said size information, The said delivery amount is characterized by the above-mentioned. The listed server. The server according to claim 7, wherein the second calculation means calculates the reward points according to which part of the data the piece is, using the distribution amount. A third storage means for storing conversion points per unit amount for each data;
The server according to any one of claims 1 to 8, wherein the second calculation means calculates the reward points using the converted points and the distribution amount of the data including the pieces. . The key request further includes device identification information assigned to the other communication device that transmits the key request,
The acquisition means further acquires device identification information assigned to the other communication device,
Charge processing for determining a discount amount using the reward points stored in the first storage means in association with the device identification information of the other communication device, and calculating a charge amount for the other communication device The server according to claim 1, further comprising: means. The key request further includes device identification information assigned to the other communication device that transmits the key request,
The acquisition means further acquires device identification information assigned to the other communication device,
The provision means which provides the privilege according to the said reward point matched with the said apparatus identification information of said another communication apparatus and memorize | stored in the said 1st memory | storage means is further provided. The server as described in any one of. The acquisition means acquires at least the data identification information and the key generation information included in the key request from a key server that receives the key request and generates the decryption key using the key generation information. The server according to any one of claims 1 to 11, characterized in that: Receiving means for receiving the key request;
Key generation means for generating the decryption key using the key generation information;
Transmission means for transmitting the decryption key to the other communication device,
The server according to claim 1, wherein the acquisition unit acquires at least the data identification information and the key generation information included in the received key request. The piece is information generated by all or a part of the plurality of communication devices that mediate transmission of the piece, and uses different temporary information and secret information respectively assigned to the plurality of communication devices. Each encrypted with a temporary symmetric key generated
The key generation information includes the device identification information and the temporary information in association with the plurality of communication devices that mediate transmission of the pieces,
And further comprising fourth storage means for storing the secret information assigned to each of the plurality of communication devices and the device identification information assigned to each communication device in association with each other.
The key generation means includes the secret information stored in association with the device identification information included in the key request and the temporary information included in the key request in association with the device identification information. The server according to claim 13, wherein the decryption key is generated using information. An information processing method executed on a server,
The piece is a part of data, which is encrypted by the communication device and transmitted from the communication device to the other communication device,
The key request for requesting a decryption key for decrypting the piece includes data identification information for identifying the data and key generation information for generating the decryption key, and the other Transmitted from the communication device,
The key generation information includes device identification information assigned to the communication device,
Obtaining the data identification information and the device identification information included in the key request;
A first calculation step of calculating a delivery amount, which is a data amount of the piece transmitted by the communication device, using the data identification information and the key generation information;
A second calculation step of calculating reward points to be given to the communication device using the distribution amount;
And a first storage control step of storing the reward points in association with the device identification information in a storage means. The piece is a part of data, which is encrypted by the communication device and transmitted from the communication device to the other communication device,
The key request for requesting a decryption key for decrypting the piece includes data identification information for identifying the data and key generation information for generating the decryption key, and the other Transmitted from the communication device,
The key generation information includes device identification information assigned to the communication device,
Obtaining means for obtaining the data identification information and the key generation information included in the key request;
First calculation means for calculating a delivery amount, which is a data amount of the piece transmitted by the communication device, using the data identification information and the key generation information;
Second calculation means for calculating reward points to be given to the communication device using the delivery amount;
A program for causing a computer to function as first storage control means for storing the reward points in association with the device identification information in a storage means.

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