JP2008148036A - Data distribution method and relay device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that an interceptor also decodes data when a decryption key for decoding encryption flows out to the interceptor in the case data distribution is performed only to a predetermined receiver by encryption. <P>SOLUTION: When data distribution is performed between a transmitter 10 and a receiver 30 via relay devices 20a, 20b, different encryption keys are used at each part of a communication path by encrypting the data using different encryption keys respectively to be transmitted by the transmitter 10 and the relay devices 20a, 20b and decoding of the data by the interceptor is avoided unless a necessary decoding key flows out at a part where the interceptor performs interception. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is used for unicast for distributing data from a transmitting device to a single receiving device or for multicast for distributing the same data from a transmitting device to a plurality of receiving devices. In particular, the present invention relates to a technique for avoiding data being stolen through a communication path.

  In recent years, data distribution using an IP network based on packet communication, such as video stream distribution and file exchange, has been widely performed. Data distribution forms are roughly classified into unicast that distributes data to a single destination and multicast that distributes the same data to a plurality of destinations.

  When it is desired to distribute data only to one or more predetermined destinations, it is necessary to take measures against data leakage such as data being intercepted through a communication path. For example, in a service in which a video stream is distributed only to a contracted user and a viewing fee is charged only from the contracted user, a user who is not contracted through a communication path can intercept data. The video will be available, making it difficult to secure the number of subscribers.

  On the other hand, there is a method of preventing data outflow by encrypting data to be distributed on the transmission side. In this method, first, the transmission side generates a pair of encryption key and decryption key for data encryption and decryption. Subsequently, the transmission side distributes the decryption key only to a predetermined recipient. Then, the transmission side encrypts and distributes the data using the encryption key. The receiving side decrypts the encrypted data using the distributed decryption key.

  In this case, even if the data is intercepted through the communication path, the encrypted data cannot be decrypted unless the interceptor has the decryption key.

  Encryption methods are roughly classified into common key encryption and public key encryption. Common key cryptography (for example, see Non-Patent Document 1) is an encryption method in which an encryption key and a decryption key are the same, and public key cryptography (for example, see Non-Patent Document 2) is an encryption key and a decryption key. Are different encryption methods. Although it is not impossible for an eavesdropper to decrypt and decrypt a cipher without using a decryption key, most of the currently used encryption methods require a large amount of computation for decryption. It can be said that decipherment is impossible.

  However, when the decryption key leaks from the receiver to the interceptor, the interceptor can decrypt the encrypted data using the decryption key. In particular, in a multicast with a large number of recipients, the decryption key is distributed to a large number of recipients, so that there is a high possibility that the decryption key will be leaked to the interceptor.

Daemon. J and Rijmen. V, “AES Proposal: Rijndael”, NIST AES Proposal, 1998 R. L. Rivest, A.M. Shamir, and L.L. Adleman, “A Method for Obtaining Digital Signatures and Public-key Cryptosystems”, Communications of the ACM, 21, 1978, pp120-126.

  As described above, since the conventional data distribution method using encryption uses a pair of encryption key and decryption key between the sender and the receiver, if the decryption key leaks to the interceptor, the interceptor is also encrypted. There is a problem that the received data can be decrypted.

  The present invention has been made under such a background, and the decryption used at the place where the eavesdropper intercepts by changing the encryption key and the decryption key according to each place of the communication path. It is an object of the present invention to provide a data distribution method and a relay device that can avoid data being decrypted by an eavesdropper unless a key is leaked.

  According to the present invention, data is transmitted from a transmitting device to a plurality of receiving devices via one or more relay devices from a unicast or transmitting device via one or more relay devices. This is a data distribution method applied to multicast to be distributed.

  Here, a feature of the present invention is that the transmitting device authenticates the downstream nearest receiving device or relay device, and the downstream nearest receiving device that succeeds in the authentication by the step of performing the authentication or Transmitting encrypted data using different encryption keys for each relay device, wherein the relay device authenticates the nearest downstream receiving device or relay device, and performs this authentication step. The data received from the upstream transmitting device or relay device is encrypted to the nearest downstream receiving device or relay device that has been successfully authenticated by using an encryption key that is different for each downstream receiving device or relay device. And performing the transfer step, and the receiving device is executing the step of decrypting the encrypted data received from the upstream.

  According to this, unless the encryption key of the encrypted data passing through each part of the communication path is different and the decryption key of the part intercepted by the eavesdropper flows out, the data not encrypted by the eavesdropper It is possible to avoid leakage.

  In addition, the transmission device or the relay device can execute a step of changing an encryption key used for encryption of the nearest downstream receiving device or relay device during data distribution.

  According to this, even if the decryption key of the location to be intercepted by the eavesdropper leaks, the decryption key of the location to be intercepted during data distribution changes, so it is impossible to decrypt with the leaked decryption key, It is possible to avoid leakage of unencrypted data to the eavesdropper.

  The relay device decrypts the encrypted data received from the upstream transmission device or relay device, and then uses the encryption key that is different for each of the latest downstream reception devices or relay devices. The step of encrypting and transferring the encrypted data again can be executed.

  According to this, every time the encrypted data distributed from the upstream passes through the relay device, it is encrypted with a different encryption key, and the encrypted data passing through each part of the communication path is encrypted. The encryption keys can be different.

  Alternatively, the relay device does not decrypt the encrypted data received from the upstream transmission device or the relay device, and the encrypted data is different for each downstream receiving device or relay device. Executing a step of further encrypting and transferring the data using an encryption key, wherein the receiving device decrypts the encrypted data received from the upstream transmitting device or relay device once or more Can be executed.

  According to this, since the decoding process in the relay device can be omitted, the configuration of the relay device can be simplified and the processing load can be suppressed.

  The present invention can also be viewed from the viewpoint of a relay device. That is, the present invention provides a method for distributing data from a transmitting device to a single receiving device via one or more relay devices, or from a transmitting device to a plurality of receiving devices via one or more relay devices. The relay device is applied to multicast for distributing data.

  Here, a feature of the present invention is that the downstream nearest receiving device or relay device is authenticated, and the downstream nearest receiving device or relay device that has been successfully authenticated by the authentication means is connected upstream. And means for transferring the data received from the transmitting device or relay device by performing encryption using a different encryption key for each of the latest downstream receiving devices or relay devices.

  In addition, it is possible to provide means for changing an encryption key used for encryption for each of the latest downstream receiving apparatuses or relay apparatuses during distribution of data.

  In addition, after decrypting the encrypted data received from the upstream transmitting device or relay device, the decrypted data is again stored using a different encryption key for each downstream receiving device or relay device. Means for encrypting and transferring can be provided.

  Alternatively, the encrypted data received from the upstream transmission device or relay device is not decrypted, and the encrypted data is used for the nearest downstream receiving device or relay device using a different encryption key. In addition, a means for performing encryption and transferring can be provided.

  The present invention can also be viewed from the viewpoint of a program. That is, the present invention is a program that, when installed in a general-purpose information processing apparatus, causes the general-purpose information processing apparatus to realize a function corresponding to the relay apparatus of the present invention.

  By recording the program of the present invention on a recording medium, the general-purpose information processing apparatus can install the program of the present invention using this recording medium. Alternatively, the program of the present invention can be directly installed on the general-purpose information processing apparatus via a network from a server that holds the program of the present invention.

  Thereby, the relay apparatus of this invention is realizable using a general purpose information processing apparatus.

  The program of the present invention includes not only a program that can be directly executed by a general-purpose information processing apparatus but also a program that can be executed by installing it on a hard disk or the like. Also included are those that are compressed or encrypted.

  According to the present invention, when data is encrypted and distributed, the decryption key leaks to the eavesdropper so that the data can be decrypted by the eavesdropper. By changing the encryption key, there is an effect that the eavesdropper cannot decrypt the data unless the decryption key used at the location where the eavesdropper intercepts.

(Premise of the whole embodiment)
As an encryption method used in the following description, common key encryption may be used, or public key encryption may be used. When the common key encryption is used, the following encryption keys and the corresponding decryption keys are the same.

(Assumptions for unicast)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a distribution form of a communication system according to an embodiment of the present invention in unicast. Here, packet communication in the IP network is assumed.

  Data transmitted from the transmission device 10 is received by the reception device 30 via the plurality of relay devices 20a and 20b. Although two relay apparatuses are connected in FIG. 1, this is an example, and an arbitrary number of one or more can be connected.

  Further, the authentication device 40 is used for the transmission device 10 and the relay devices 20a and 20b to authenticate the relay device and the reception device connected downstream, respectively. The authentication device 40 may be installed at any position on the IP network as long as it can communicate with the transmission device 10 and the relay devices 20a and 20b.

  In addition, there is a possibility that data flowing through the communication path may be intercepted by the interceptor 50 on the communication path between the transmission device 10 and the reception device 30. In FIG. 1, as an example, the interceptor 50 intercepts data flowing between the relay device 20 a and the relay device 20 b, but in practice, it is intercepted at an arbitrary location between the transmission device 10 and the reception device 30. There is a possibility that.

(First embodiment: Example of decoding by relay node by unicast)
FIG. 2 is a block diagram illustrating the communication system according to the embodiment shown in FIG. 1 and functionally expanding the inside of the relay device 20 having a function of decrypting encrypted data. In FIG. 2, the transmission device 10 is connected upstream of the relay device 20 and the reception device 30 is connected downstream. However, similarly to FIG. 1, the relay device may be connected upstream of the relay device 20, A relay device may be connected downstream.

  The relay device 20 receives a transfer request from a downstream device, an authentication result and an encryption key and a decryption key from an authentication device, receives encrypted data from an upstream device, and authenticates the authentication device. Request, a transfer request to an upstream device, a communication I / F 21 for transmitting encrypted data to a downstream device, and an authentication request for authentication of a downstream device, and an authentication result from the authentication device and A transfer request processing unit 22 that transmits information on the encryption key and the decryption key to the transfer processing unit 23, the decryption unit 24, and the encryption unit 25, and a transfer processing unit that determines whether or not data from the upstream is to be transferred downstream 23, a decryption unit 24 for decrypting the encrypted data from the upstream, and an encryption unit 25 for encrypting the decrypted data.

  Based on the distribution form of FIG. 1, an embodiment in which the relay device of FIG. 2 is used will be described with reference to the sequence diagrams of FIGS.

  FIG. 3 is a sequence diagram showing a procedure for authenticating each device used for distribution. The receiving device 30 that wants to receive data from the transmitting device 10 first transmits a transfer request S101 upstream. The transfer request S101 includes information for authenticating the receiving device 30, for example, the IP address of the receiving device 30, a user name, a password, and the like.

  The transfer request S101 is received by the relay device 20b upstream of the reception device 30. Thereafter, the relay device 20b determines, as authentication request S102, information for authenticating the receiving device 30 included in the transfer request S101 in order to determine whether or not data from upstream can be transferred to the receiving device 30. It transmits to the authentication device 40.

  The authentication device 40 receives the authentication request S102 and attempts to authenticate the reception device 30. This is performed, for example, by collating the database inside the authentication device 40 with the information for authentication included in the authentication request S102.

  Next, the authentication device 40 requests the authentication result, that is, information on whether or not the authentication is successful, and a pair of encryption key (encryption key # 1) and decryption key (decryption key # 1). It transmits to the relay apparatus 20b which is the transmission source of S102 (S103). The encryption key # 1 and the decryption key # 1 may be generated randomly by the authentication device 40 or based on a certain rule.

  The relay device 20b receives the authentication result S103 from the authentication device 40. If the authentication fails, the relay device 20b does not perform the process described below and does not transfer data from the upstream to the reception device 30. On the other hand, if the authentication is successful, the relay device 20b stores the encryption key # 1 received from the authentication device 40 and transmits the decryption key # 1 to the authenticated receiving device 30 (S104). . The receiving device 30 stores the received decryption key # 1.

  Next, the relay device 20b transmits a transfer request S105 to the upstream in order to request data from the upstream. Similarly to the transfer request S101, the transfer request S105 includes information for authenticating the relay device 20b.

  The transfer request S105 is received by the relay device 20a upstream of the relay device 20b. Thereafter, in order to determine whether or not the data from the upstream side may be transferred to the relay device 20b, the relay device 20a uses information for authenticating the relay device 20b included in the transfer request S105 as the authentication request S106. To the authentication device 40.

  The authentication device 40 receives the authentication request S106 and attempts to authenticate the relay device 20b in the same manner as when the authentication request S102 is received, and this authentication result, a pair of encryption key (encryption key # 2) and decryption The encryption key (decryption key # 2) is transmitted to the relay device 20a (S107).

  The relay device 20a receives the authentication result S107 from the authentication device 40. If the authentication fails, the relay device 20a does not perform the processing described below and does not transfer data from the upstream to the relay device 20b. On the other hand, if the authentication is successful, the relay device 20a stores the encryption key # 2 received from the authentication device 40 and transmits the decryption key # 2 to the authenticated relay device 20b (S108). . The relay device 20b stores the received decryption key # 2.

  Next, the relay device 20a transmits a transfer request S109 to the upstream in order to request data from the upstream. Similar to the transfer requests S101 and S105, the transfer request S109 includes information for authenticating the relay device 20a.

  The transfer request S109 is received by the transmission device 10 upstream of the relay device 20a. Thereafter, in order to determine whether or not the data may be transmitted to the relay device 20a, the transmission device 10 uses the information for authenticating the relay device 20a included in the transfer request S109 as the authentication request S110. Send to.

  The authentication device 40 receives the authentication request S110, and similarly to the case where the authentication requests S102 and S106 are received, the authentication device 40 attempts to authenticate the relay device 20a, and the authentication result and a pair of encryption keys (encryption key # 3). The decryption key (decryption key # 3) is transmitted to the transmitting apparatus 10 (S111).

  The transmission device 10 receives the authentication result S111 from the authentication device 40, and when the authentication fails, the processing described below is not performed and data is not transmitted to the relay device 20a. On the other hand, when the authentication is successful, the transmission device 10 stores the encryption key # 3 received from the authentication device 40 and transmits the decryption key # 3 to the authenticated relay device 20a (S112). . The relay device 20a stores the received decryption key # 3.

  FIG. 4 is a sequence diagram illustrating a procedure for performing data distribution. First, the transmitting apparatus 10 encrypts data to be transmitted using the stored encryption key # 3 (S201), and transmits it to the downstream relay apparatus 20a (S202).

  The relay device 20a first decrypts the data encrypted with the encryption key # 3 received from the upstream using the stored decryption key # 3 (S203), and then stores the stored encryption. Encryption is performed using the encryption key # 2 (S204), and is transmitted to the downstream relay device 20b (S205).

  The relay device 20b first decrypts the data encrypted with the encryption key # 2 received from the upstream using the stored decryption key # 2 (S206), and then stores the stored encryption. Encryption is performed using the encryption key # 1 (S207) and transmitted to the downstream receiving device 30 (S208).

  Then, the receiving device 30 decrypts the data encrypted with the encryption key # 1 received from the upstream using the stored decryption key # 1 (S209). Through the above procedure, the receiving device 30 can obtain unencrypted data.

  Here, as shown in FIG. 1, it is considered that the eavesdropper 50 has intercepted the data flowing through the communication path between the relay device 20a and the relay device 20b. In the conventional method, since the same encryption key and decryption key are used in all parts of the communication path, if the decryption key leaks from the receiver to the interceptor 50, the data that the interceptor 50 has encrypted is transferred. By decrypting, unencrypted data is leaked to the interceptor 50.

  On the other hand, when data distribution is performed according to the above procedure, since the encryption key and the decryption key used in each part of the communication path are different from each other, the decryption key # 1 held by the receiving device 30 is the interceptor 50. Even if the data is leaked, since the data intercepted by the interceptor 50 is encrypted with the encryption key # 2, the interceptor 50 cannot decrypt the encrypted data. As long as the decryption key (decryption key # 1) of the part intercepted by the interceptor 50 does not flow out to the interceptor 50, it is possible to prevent the unencrypted data from leaking out to the interceptor 50.

  In the above procedure, each encryption key and each decryption key transmitted from the authentication device to the transmission device and the relay device, and from the transmission device or the relay device to the other relay device or the reception device are the communication path used for data distribution. May be transmitted using a different route, or the encryption key and the decryption key themselves may be encrypted and transmitted by a predetermined encryption method. Thereby, it is possible to avoid the interception of the encryption key and the decryption key exchanged by the interceptor through the communication path.

(Second Example: Example of Changing Encryption Key and Decryption Key During Distribution in First Example)
FIG. 5 is a sequence diagram showing a procedure for changing the encryption key and the decryption key during data distribution according to the procedure of FIG. In this case, the authentication device 40 generates and transmits a new encryption key and decryption key to the partner device that has received the authentication request so far when the key is changed. This key change may be performed at random time intervals or at intervals according to a certain rule.

  First, the authentication device 40 generates a new pair of encryption key (encryption key # 4) and decryption key (decryption key # 4), and transmits them to the relay device 20b (S301). The encryption key and the decryption key may be randomly generated by the authentication device 40 or may be generated based on a certain rule.

  The relay device 20b stores the received encryption key # 4 and transmits the decryption key # 4 to the downstream receiving device 30 (S302). Thereafter, the encryption key # 4 is used in place of the encryption key # 1 for data encryption in the relay device 20b, and the decryption key # 1 is used for data decryption in the reception device 30. Instead, decryption key # 4 is used.

  Next, authentication apparatus 40 uses a new pair of encryption key (encryption key # 5) and decryption key (decryption key # 5) in the same manner as encryption key # 4 and decryption key # 4. It is generated and transmitted to the relay device 20a (S303).

  The relay device 20a stores the received encryption key # 5 and transmits the decryption key # 5 to the downstream relay device 20b (S304). Thereafter, the encryption key # 5 is used instead of the encryption key # 2 for data encryption in the relay device 20a, and the decryption key # 2 is used for data decryption in the relay device 20b. Instead, decryption key # 5 is used.

  Next, authentication apparatus 40 uses a new pair of encryption key (encryption key # 6) and decryption key (decryption key # 6) in the same manner as encryption key # 4 and decryption key # 4. Is generated and transmitted to the transmission device 10 (S305).

  The transmission device 10 stores the received encryption key # 6 and transmits the decryption key # 6 to the downstream relay device 20a (S306). Thereafter, the encryption key # 6 is used in place of the encryption key # 3 for data encryption in the transmitting apparatus 10, and the decryption key # 3 is used for data decryption in the relay apparatus 20a. Instead, decryption key # 6 is used.

  With the above procedure, the encryption key and the decryption key used at each location of the communication path are changed during data distribution. As a result, even if the decryption key used at the place where the interceptor 50 intercepted leaked to the interceptor 50, the encryption key and the decryption key used for data distribution change with time, so the interceptor 50 However, it is possible to avoid continuously obtaining unencrypted data.

  In the above procedure, each encryption key and each decryption key transmitted from the authentication device to the transmission device and the relay device, and from the transmission device or the relay device to another relay device or the reception device are the communication path used for data distribution. May be transmitted using a different route, or the encryption key and the decryption key themselves may be encrypted and transmitted by a predetermined encryption method. Thereby, it is possible to avoid the interception of the encryption key and the decryption key exchanged by the interceptor through the communication path.

(Third embodiment: Example in which decoding is not performed at a relay node in unicast)
FIG. 6 is a block diagram showing the functional development of the inside of the relay device 20 that constitutes the communication system according to the embodiment shown in FIG. 1 and does not have a function of decrypting encrypted data. The difference from FIG. 2 is that it does not have a decoding unit for decoding data from upstream.

  Based on the distribution form of FIG. 1, an embodiment in which the relay apparatus of FIG. 6 is used will be described with reference to the sequence diagrams of FIGS.

  FIG. 7 is a sequence diagram showing a procedure for authenticating each device used for distribution. A difference from FIG. 3 is that all the decryption keys transmitted from the authentication device 40 are transmitted to the reception device 30. That is, the decryption key # 2 (S407) transmitted from the authentication device 40 to the relay device 20a is transmitted to the reception device 30 via the relay device 20b (S408, S409). The receiving device 30 stores the received decryption key # 2. The decryption key # 3 (S412) transmitted from the authentication device 40 to the transmission device 10 is transmitted to the reception device 30 via the relay devices 20a and 20b (S413, S414, and S415). The receiving device 30 stores the received decryption key # 3.

  FIG. 8 is a sequence diagram illustrating a procedure for performing data distribution. A difference from FIG. 4 is that the relay apparatuses 20a and 20b do not perform decoding, and the receiving apparatus 30 performs all decoding. That is, the relay device 20a does not decrypt the data encrypted with the encryption key # 3 received from the upstream (S502), and further encrypts the data using the encryption key # 2 (S503). It transmits to 20b (S504). The relay device 20b does not decrypt the encrypted data (S504) received from the upstream side, further encrypts it using the encryption key # 1 (S505), and transmits it to the receiving device 30 (S506). The receiving device 30 decrypts the data encrypted a plurality of times using the stored decryption key # 1, decryption key # 2, and decryption key # 3 (S507).

  By the above procedure, when the relay device does not have the processing performance to perform the decryption process, the relay device does not perform the decryption, and the receiver device performs the decryption collectively, so that it is used at each part of the communication path. It is possible to perform data distribution in which the encryption key and the decryption key to be transmitted are different.

  In addition, as shown in FIG. 1, when the interceptor 50 intercepts data flowing through the communication path, the intercepted data is encrypted one or more times, so the interceptor 50 decrypts the data. Therefore, it is necessary to obtain one or more decryption keys, and it is difficult for the interceptor 50 to decrypt the data.

  In the above procedure, each encryption key and each decryption key transmitted from the authentication device to the transmission device and the relay device, and from the transmission device or the relay device to another relay device or the reception device are the communication path used for data distribution. May be transmitted using a different route, or the encryption key and the decryption key themselves may be encrypted and transmitted by a predetermined encryption method. Thereby, it is possible to avoid the interception of the encryption key and the decryption key exchanged by the interceptor through the communication path.

(Fourth embodiment: Example of changing encryption key and decryption key during distribution in the third embodiment)
FIG. 9 is a sequence diagram showing a procedure for changing the encryption key and the decryption key during data distribution in the procedure of FIG. The difference from FIG. 5 is that all the decryption keys transmitted from the authentication device 40 are transmitted to the reception device 30. That is, the decryption key # 4 (S601) transmitted from the authentication device 40 to the relay device 20b is transmitted to the reception device 30 via the relay device 20b (S602). The receiving device 30 stores the received decryption key # 4 and uses the decryption key # 4 for decryption.

  In addition, the decryption key # 5 (S603) transmitted from the authentication device 40 to the relay device 20a is transmitted to the reception device 30 via the relay device 20b (S604, S605). The receiving device 30 stores the received decryption key # 5, and uses the decryption key # 5 instead of the decryption key # 2 for decryption.

  The decryption key # 6 (S606) transmitted from the authentication device 40 to the transmission device 10 is transmitted to the reception device 30 via the relay devices 20a and 20b (S607, S608, and S609). The receiving device 30 stores the received decryption key # 6, and uses the decryption key # 6 instead of the decryption key # 3 for decryption.

  With the above procedure, the encryption key and the decryption key used at each location of the communication path are changed during data distribution. As a result, even if one or more decryption keys used at a place where the interceptor 50 intercepted leaked to the interceptor 50, the encryption key and the decryption key used for data distribution are changed over time. Since it changes, it can be avoided that the interceptor 50 continues to obtain unencrypted data.

  In the above procedure, each encryption key and each decryption key transmitted from the authentication device to the transmission device and the relay device, and from the transmission device or the relay device to another relay device or the reception device are the communication path used for data distribution. May be transmitted using a different route, or the encryption key and the decryption key themselves may be encrypted and transmitted by a predetermined encryption method. Thereby, it is possible to avoid the interception of the encryption key and the decryption key exchanged by the interceptor through the communication path.

(Assumptions for multicast)
FIG. 10 shows a distribution form of a communication system according to an embodiment of the present invention in multicast. The difference from FIG. 1 is that data transmitted from the transmission device 10 is received by a plurality of reception devices 30a, 30b, 30c, and 30d. For this reason, the relay apparatuses 20c, 20d, and 20e transmit the data received from the upstream to a plurality of downstream receiving apparatuses or relay apparatuses. Here, in the figure, three relay devices and four receiving devices are connected, but this is an example, and any number of one or more devices can be connected.

  In the figure, two relay devices or receiving devices are connected downstream of the relay device, but this is an example, and one or more arbitrary number of relay devices or receiving devices can be connected. In addition, the interceptor 50 intercepts data flowing between the relay device 20c and the relay device 20d, but in practice, the interceptor 50 intercepts data at any location between the transmission device 10 and the reception devices 30a, 30b, 30c, and 30d. There is a possibility that.

(Fifth embodiment: Example of decoding by relay node in multicast)
FIG. 11 is a block diagram showing a functional development of the inside of the relay apparatus 20 that constitutes the communication system according to the embodiment shown in FIG. 10 and has a function of decrypting encrypted data. The difference from FIG. 2 is that the transfer processing unit 23 corresponds to a plurality of downstream devices, and has a function of copying data received from the upstream and transmitting the data to the plurality of devices. In the figure, the transmitting device is connected upstream, but another relay device may be connected. In the figure, two receiving apparatuses are connected downstream, but this is an example, and one or more arbitrary number of relay apparatuses and receiving apparatuses can be connected.

  Based on the distribution form of FIG. 10, an embodiment in which the relay device of FIG. 11 is used will be described with reference to the sequence diagrams of FIGS. Here, for simplification of description, a case where data is distributed only to the receiving devices 30a and 30b in the distribution form of FIG. 10 will be described below. Data can be distributed to the receiving devices 30c and 30d in the same procedure as described below.

  FIG. 12 is a sequence diagram illustrating a procedure for authenticating each device used for distribution. The difference from FIG. 3 is that the two receiving devices 30a and 30b are authenticated. That is, first, authentication of the receiving device 30a and the relay devices 20d and 20c is performed in the same procedure as in FIG. Thereafter, when the transfer request S713 is received from the new receiving device 30b, the relay device 20d transmits an authentication request S714 for authenticating the receiving device 30b to the authenticating device 40 by means similar to the authentication of the receiving device 30a. The authentication device 40 transmits the newly generated encryption key # 4 and decryption key # 4 together with the authentication result to the relay device 20d (S715), and the relay device 20d stores the encryption key # 4. At the same time, the decryption key # 4 is transmitted to the receiving device 30b, and the receiving device 30b stores the decryption key # 4.

  FIG. 13 is a sequence diagram illustrating a procedure for performing data distribution. The difference from FIG. 4 is that the relay device 20d transmits the encrypted data not only to the reception device 30a but also to the reception device 30b. That is, the relay device 20d decrypts the data encrypted with the encryption key # 2 received from the upstream with the decryption key # 2 (S806) and encrypts with the encryption key # 1 in the same procedure as in FIG. (S807) The data is transmitted to the receiving device 30a (S808), and the data decrypted with the decryption key # 2 is encrypted with the encryption key # 4 (S810) and transmitted to the receiving device 30b (S811). The receiving device 30a decrypts the encrypted data received from the upstream using the stored decryption key # 1 (S809). Similarly, the receiving device 30b decrypts the encrypted data received from the upstream using the stored decryption key # 4 (S812).

  In particular, in the case of multicast, if the same encryption key and decryption key are used at all points in the communication path as in the past, the decryption key is distributed to many recipients, so decryption is possible. There is a high possibility that the key will be leaked to the interceptor 50, and there is a high possibility that unencrypted data will be leaked to the interceptor 50. On the other hand, in the above procedure, since different encryption keys and decryption keys can be used in each part of the communication path, even if the decryption key in the interceptor 50 leaks from the receiver, the interceptor As long as the decryption key used at the location where 50 is intercepted does not flow out, it is possible to avoid leakage of unencrypted data to the interceptor 50.

  In the above procedure, each encryption key and each decryption key transmitted from the authentication device to the transmission device and the relay device, and from the transmission device or the relay device to another relay device or the reception device are the communication path used for data distribution. May be transmitted using a different route, or the encryption key and the decryption key themselves may be encrypted and transmitted by a predetermined encryption method. Thereby, it is possible to avoid the interception of the encryption key and the decryption key exchanged by the interceptor through the communication path.

(Sixth embodiment: Example of changing encryption key and decryption key during distribution in the fifth embodiment)
FIG. 14 is a sequence diagram showing a procedure for changing the encryption key and the decryption key during data distribution in the procedure of FIG. The difference from FIG. 5 is that the authentication device 40 transmits the encryption key and the decryption key to the two receiving devices 30a and 30b. That is, in the same procedure as in FIG. 5, the receiving device 30a, the relay devices 20d and 20c, and the transmitting device 10 are newly encrypted with an encryption key # 5, an encryption key # 6, an encryption key # 7, a decryption key # 5, and a decryption key. After transmitting the encryption key # 6 and the decryption key # 7 (S901, S902, S903, S904, S905, S906), a new encryption key # 8 and a decryption key # 8 are transmitted to the receiving device 30b ( S907, S908).

  Thereafter, the transmitting device 10 decrypts the encryption key # 7 instead of the encryption key # 3, and the relay device 20c decrypts the encryption key # 6 instead of the encryption key # 2 and decryption instead of the decryption key # 3. The relay device 20d receives the key # 7, the encryption key # 5 instead of the encryption key # 1, the encryption key # 8 instead of the encryption key # 4, and the decryption key # 6 instead of the decryption key # 2. The receiving device 30a uses the decryption key # 5 instead of the decryption key # 1, and the receiving device 30b uses the decryption key # 8 instead of the decryption key # 4.

  With the above procedure, the encryption key and the decryption key used at each location of the communication path are changed during data distribution. As a result, even if the decryption key used at the place where the interceptor 50 intercepted leaked to the interceptor 50, the encryption key and the decryption key used for data distribution change with time, so the interceptor 50 However, it is possible to avoid continuously obtaining unencrypted data.

  In the above procedure, each encryption key and each decryption key transmitted from the authentication device to the transmission device and the relay device, and from the transmission device or the relay device to another relay device or the reception device are the communication path used for data distribution. May be transmitted using a different route, or the encryption key and the decryption key themselves may be encrypted and transmitted by a predetermined encryption method. Thereby, it is possible to prevent the encryption key and the decryption key exchanged by the interceptor through the communication path from being intercepted.

(Seventh embodiment: Example in which decoding is not performed at a relay node in multicast)
FIG. 15 is a block diagram showing the functional development of the inside of the relay device 20 that constitutes the communication system according to the embodiment shown in FIG. 10 and does not have a function of decrypting encrypted data. The difference from FIG. 11 is that it does not have a decoding unit for decoding data from upstream.

  Based on the distribution form of FIG. 10, an embodiment in which the relay device of FIG. 15 is used will be described with reference to the sequence diagrams of FIGS. Here, for simplification of description, a case where data is distributed only to the receiving devices 30a and 30b in the distribution form of FIG. 10 will be described below. Data can be distributed to the receiving devices 30c and 30d in the same procedure as described below.

  FIG. 16 is a sequence diagram illustrating a procedure for authenticating each device used for distribution. The difference from FIG. 12 is that each relay device stores the decryption key received from the authentication device 40 or the upstream transmission device or relay device and then forwards it to the downstream relay device or reception device.

  That is, the decryption key # 1 (S1003) transmitted from the authentication device 40 is received and stored by the relay device 20d, then transferred to the downstream receiving device 30a, and stored in the receiving device 30a. Similarly, decryption key # 2 is stored in relay device 20c, then transferred to relay device 20d, stored in relay device 20d, transferred to receiving device 30a, and stored in receiving device 30a. Similarly, the decryption key # 3 is stored in the relay device 20c, then transferred to the relay device 20d, stored in the relay device 20d, transferred to the receiving device 30a, and stored in the receiving device 30a.

  Further, as another point of difference in the procedure of FIG. 16 from FIG. 12, when the relay device receives a transfer request from a new receiving device, the relay device receives the request from the authenticating device after authenticating the receiving device. This means that all the decryption keys received from the upstream transmitting device or relay device so far are transferred to the receiving device together with the decrypting key.

  That is, when the transfer request S1016 is received from the new receiving device 30b, the authentication request S1017 is transmitted to the authenticating device 40, and the decryption key # 4 received from the authenticating device 40 after the authentication is transmitted upstream. The decryption key # 2 and the decryption key # 3, which are decryption keys received from the relay device 20c, are transferred to the authenticated receiving device 30b.

  FIG. 17 is a sequence diagram illustrating a procedure for performing data distribution. The difference from FIG. 13 is that the relay apparatuses 20c and 20d do not perform decoding, and the receiving apparatuses 30a and 30b perform all decoding.

  That is, the relay device 20c does not decrypt the encrypted data S1102 received from the upstream side, further encrypts it using the encryption key # 2 (S1103), and transmits it to the relay device 20d (S1104). The relay device 20d does not decrypt the encrypted data S1104 received from the upstream side, further encrypts it using the encryption key # 1 (S1105), transmits it to the reception device 30a (S1106), and encrypts it. Data S1104 prior to encryption with key # 1 is further encrypted using encryption key # 4 (S1108) and transmitted to receiving apparatus 30b (S1109). The receiving device 30a decrypts the data S1106 received from upstream using the stored decryption key, decryption key # 1, decryption key # 2, and decryption key # 3 (S1107). In addition, the receiving device 30b decrypts the data S1109 received from the upstream using the stored decryption key, decryption key # 4, decryption key # 2, and decryption key # 3 (S1110).

  By the above procedure, when the relay device does not have the processing performance to perform the decryption process, the relay device does not perform the decryption, and the receiver device performs the decryption collectively, thereby using it at each part of the communication path. Data distribution in which the encryption key and the decryption key to be transmitted are different can be performed.

  Further, as shown in FIG. 15, when the interceptor 50 intercepts data flowing through the communication path, the intercepted data is encrypted one or more times, so the interceptor 50 decrypts the data. Therefore, it is necessary to obtain one or more decryption keys, and it is difficult for the interceptor 50 to decrypt the data.

  In the above procedure, each encryption key and each decryption key transmitted from the authentication device to the transmission device and the relay device, and from the transmission device or the relay device to another relay device or the reception device are the communication path used for data distribution. May be transmitted using a different route, or the encryption key and the decryption key themselves may be encrypted and transmitted by a predetermined encryption method. Thereby, it is possible to avoid the interception of the encryption key and the decryption key exchanged by the interceptor through the communication path.

(Eighth embodiment: Example of changing encryption key and decryption key during distribution in the seventh embodiment)
FIG. 18 is a sequence diagram showing a procedure for changing the encryption key and the decryption key during data distribution in the procedure of FIG. The difference from FIG. 14 is that each relay device stores the decryption key received from the authentication device 40 and transfers it downstream, and the decryption received by each relay device from the upstream transmission device or relay device. The key is that the key is stored and then transferred to all downstream relay devices or receiving devices.

  That is, the relay device 20d stores the decryption key # 5 (S1201) received from the authentication device 40 and transfers it to the reception device 30a (S1202). The decryption key # 6 (S1203) transmitted from the authentication device 40 is stored in the relay device 20c and then transferred to the relay device 20d (S1204). After being stored in the relay device 20d, the decryption key # 6 (S1203) The data is transferred to all the downstream receiving devices 30a and 30b (S1205, S1206).

  Similarly, the decryption key # 7 (S1207, S1208) is stored in the relay device 20c and then transferred to the relay device 20d (S1209). After being stored in the relay device 20d, all the reception downstream of the relay device 20d is received. It is transferred to the devices 30a and 30b (S1210, S1211). The decryption key # 8 (S1212) is stored in the relay device 20d and then transferred to the receiving device 30d (S1213). Thereafter, the receiving device 30a uses the decryption key # 5, the decryption key # 6, and the decryption key # 7 instead of the decryption key # 1, the decryption key # 2, and the decryption key # 3. The receiving device 30b uses a decryption key # 6, a decryption key # 7, and a decryption key # 8 instead of the decryption key # 2, the decryption key # 3, and the decryption key # 4.

  With the above procedure, the encryption key and the decryption key used at each location of the communication path are changed during data distribution. Thereby, even if one or more decryption keys used at the place where the interceptor 50 intercepted leaked to the interceptor 50, the encryption key and decryption key used for data distribution change with time, It can be avoided that the eavesdropper 50 continuously obtains unencrypted data.

  In the above procedure, each encryption key and each decryption key transmitted from the authentication device to the transmission device and the relay device, and from the transmission device or the relay device to another relay device or the reception device are the communication path used for data distribution. May be transmitted using a different route, or the encryption key and the decryption key themselves may be encrypted and transmitted by a predetermined encryption method. Thereby, it is possible to avoid the interception of the encryption key and the decryption key exchanged by the interceptor through the communication path.

(Ninth Example: Program Example)
The ninth embodiment is a program that, when installed in a general-purpose information processing apparatus, causes the general-purpose information processing apparatus to realize a function corresponding to the relay apparatus of the present embodiment.

  By recording the program of this embodiment on a recording medium, the general-purpose information processing apparatus can install the program of this embodiment using this recording medium. Alternatively, the program of this embodiment can be installed directly on the general-purpose information processing apparatus via a network from a server holding the program of this embodiment.

  Thereby, the function corresponding to the relay apparatus of a present Example is realizable using a general purpose information processing apparatus.

  The program of this embodiment includes not only a program that can be directly executed by a general-purpose information processing apparatus but also a program that can be executed by installing it on a hard disk or the like. Also included are those that are compressed or encrypted.

  According to the present invention, for example, in a paid data distribution service via a network, it is difficult for a malicious third party to obtain paid data for free, and the reliability of the paid data distribution service can be improved. It can contribute to the acquisition of service users and can contribute to the improvement of service quality.

The figure which shows the delivery form of the communication system by one Embodiment in the unicast of this invention. The block diagram of the relay apparatus which comprises the communication system by the form which a relay apparatus decodes in the unicast of this invention. The sequence diagram which showed the procedure which authenticates each apparatus in one Embodiment in which a relay apparatus decodes in the unicast of this invention. The sequence diagram which showed the procedure which performs data delivery in one Embodiment which a relay apparatus decodes in the unicast of this invention. The sequence diagram which showed the procedure which changes an encryption key and a decryption key during data delivery in one Embodiment which a relay apparatus decodes in the unicast of this invention. The block diagram of the relay apparatus which comprises the communication system by the form by which a relay apparatus does not decode in the unicast of this invention. The sequence diagram which showed the procedure which authenticates each apparatus in one Embodiment in which a relay apparatus does not decode in the unicast of this invention. The sequence diagram which showed the procedure which performs data delivery in one Embodiment in which a relay apparatus does not decode in the unicast of this invention. The sequence diagram which showed the procedure which changes an encryption key and a decryption key during data delivery in one Embodiment in which a relay apparatus does not decrypt in the unicast of this invention. The figure which shows the delivery form of the communication system by one Embodiment in the multicast of this invention. The block diagram of the relay apparatus which comprises the communication system by the form which a relay apparatus decodes in the multicast of this invention. The sequence diagram which showed the procedure which authenticates each apparatus in one Embodiment which a relay apparatus decodes in the multicast of this invention. The sequence diagram which showed the procedure which performs data delivery in one Embodiment which a relay apparatus decodes in the multicast of this invention. The sequence diagram which showed the procedure which changes an encryption key and a decryption key during data delivery in one Embodiment which a relay apparatus performs the decoding in the multicast of this invention. The block diagram of the relay apparatus which comprises the communication system by the form by which a relay apparatus does not decode in the multicast of this invention. The sequence diagram which showed the procedure which authenticates each apparatus in one Embodiment in which the relay apparatus does not decode in the multicast of this invention. The sequence diagram which showed the procedure which performs data delivery in one Embodiment in which the relay apparatus does not decode in the multicast of this invention. The sequence diagram which showed the procedure which changes an encryption key and a decryption key during data delivery in one Embodiment in which the relay apparatus does not decrypt in the multicast of this invention.

Explanation of symbols

10 Transmitting devices 20, 20a, 20b, 20c, 20d, 20e Relay device 21 Communication I / F
22 Transfer request processing unit 23 Transfer processing unit 24 Decryption unit 25 Encryption unit 30, 30a, 30b, 30c, 30d Receiving device 40 Authentication device 50 Interceptor

Claims (9)

Unicast that distributes data from a transmitting device to one receiving device via one or more relay devices, or multicast that distributes data from a transmitting device to multiple receiving devices via one or more relay devices In the data distribution method applied,
The transmitter is
Authenticating the nearest downstream receiving device or relay device; and
Performing the step of transmitting the data encrypted using a different encryption key for each of the latest downstream receiving devices or relay devices that have been successfully authenticated by the step of performing the authentication, and
The relay device is
Authenticating the nearest downstream receiving device or relay device; and
The encryption key that is different for each of the nearest downstream receiving device or relay device and the data received from the upstream sending device or relay device to the nearest downstream receiving device or relay device that has been successfully authenticated by the step of performing authentication. And performing the encryption and transfer step using
The receiving apparatus executes a step of decrypting encrypted data received from upstream.   2. The data distribution method according to claim 1, wherein the transmission device or the relay device executes a step of changing an encryption key used for encryption for the nearest downstream receiving device or relay device during data distribution.   The relay device decrypts the encrypted data received from the upstream transmission device or relay device, and then decrypts the encrypted data using a different encryption key for each of the latest downstream receiving devices or relay devices. 3. The data distribution method according to claim 1, wherein the step of encrypting and transferring the data again is executed. The relay device does not decrypt the encrypted data received from the upstream transmission device or the relay device, and encrypts the encrypted data for each of the latest downstream receiving devices or relay devices. Perform the steps of further encryption and transfer using the key,
The data distribution method according to claim 1 or 2, wherein the receiving device executes a step of decrypting data encrypted once or more received from an upstream transmission device or relay device one or more times. Unicast that distributes data from a transmitting device to one receiving device via one or more relay devices, or multicast that distributes data from a transmitting device to multiple receiving devices via one or more relay devices In the relay device to be applied,
Means for authenticating the nearest receiving device or relay device downstream;
The encryption key that is different from the data received from the upstream transmitting device or relay device for each downstream receiving device or relay device that has been successfully authenticated by the means for performing authentication. And a means for performing transfer using encryption.   6. The relay apparatus according to claim 5, further comprising means for changing an encryption key used for encryption of the nearest downstream receiving apparatus or relay apparatus during data distribution.   After decrypting the encrypted data received from the upstream transmission device or relay device, the decrypted data is re-encrypted using a different encryption key for each of the latest downstream receiving devices or relay devices. 7. The relay apparatus according to claim 5 or 6, further comprising a transfer unit.   Without decrypting the encrypted data received from the upstream transmission device or relay device, the encrypted data is further transferred using a different encryption key for each of the latest downstream reception devices or relay devices. 7. The relay apparatus according to claim 5, further comprising means for performing encryption and transferring.   A program that, when installed in a general-purpose information processing device, causes the general-purpose information processing device to realize a function corresponding to the relay device according to any one of claims 5 to 8.

Images