JP2009239496A - Data communication method using key encryption method, data communication program, data communication program storage medium, and data communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data communication method for attaining high security. <P>SOLUTION: A communication network system includes a server 10, a first terminal 20, and a second terminal 30 which are connected to each other via a network. The method for performing data communication by way of the server between the first and second terminals includes: (a) a step of allowing the first and second terminals to generate encryption keys and decoding keys corresponding to the encryption keys, respectively ; (b) a step of allowing the first or second terminal to receive the encryption key generated by the terminal itself from the other terminal; (c) a step of allowing one terminal to encrypt data by the use of the received encryption key; (d) a step of allowing one terminal to transmit the encrypted data to the other terminal; and (e) a step of allowing the other terminal to decode the received data by the use of the decoding key generated by the other terminal when receiving the encrypted data. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a data communication method using a key encryption method, a program that causes a computer to execute the method, a computer-readable medium that stores the program, and a data communication system that executes the communication method.

  With the spread of the Internet, communication terminals such as computers can exchange various information with other communication terminals in real time via a network. However, since various users access the Internet, there is a possibility that information exchanged may be wiretapped or tampered with by a third party unrelated to the information. Furthermore, there is a possibility that a malicious third party impersonates another person and transmits inappropriate information (hereinafter, simply referred to as “spoofing” in this specification). For this reason, when exchanging information via the Internet, it is necessary to take security measures for the network system in consideration of the possibility of the above actions.

  A general security measure is to encrypt information. The transmission source encrypts the information and sends it to the transmission destination via the network, and the transmission destination decrypts the encrypted information and reads it back to the original state. The intent of encryption is to prevent information from being read by a third party, thereby preventing eavesdropping. In addition, the encryption technology can also check the consistency between the information sent by a method such as hash check and the received information, and it is also possible to check whether the information has been tampered with. is there. Furthermore, since the destination of information can be confirmed by using an electronic signature method, impersonation can be prevented. As described above, if the encryption technique is used, the security of the system can be strengthened, and is now widely used.

It is well known in the art that such information encryption and decryption is performed using special information called a “key” (see, for example, Patent Documents 1 to 3). With this key, a process of “keying” is performed when encrypting, and a process of “opening a key” is performed when decrypting. There are two types of keys: “encryption key” used for encryption and “decryption key” used for decryption (hereinafter, both keys are collectively referred to as a “key pair”). There is a strict management. If the decryption key is passed to a third party, the encrypted information will be decrypted and read after eavesdropping.
JP-A-11-340969 JP 2000-278258 A JP 2006-140743 A

When sending information encrypted using the key, the transmission source needs to pass the decryption key to the transmission destination in advance. If the decryption key is sent via the network, it may be eavesdropped and passed to a third party. Therefore, the decryption key must be stored in a storage medium such as a flexible disk or a CD-ROM and handed over or mailed. However, if this storage medium is not properly managed, there is a risk of passing to a third party. Also, mailing takes time for logistics and impairs the convenience of the Internet. In addition, the economic burden associated with mailing increases, and the cumbersome work of mailing procedures occurs, making it difficult to change the key regularly.

  The present invention was devised in view of the above problems, and an object of the present invention is to securely transmit a key via a network in a data communication using a key encryption method, and to easily generate a key pair. A data communication method capable of changing the above, a program that causes a computer to execute the method, a computer-readable medium that stores the program, and a data communication system that executes the communication method are provided.

  Another subject of the present invention is a data communication method capable of realizing strong security in data communication using a key encryption method, a program for causing a computer to execute the method, a computer-readable medium for storing the program, A data communication system for executing the communication method is provided.

  The invention of claim 1 devised to solve the above-mentioned problems is a communication network system comprising a server, a first terminal, and a second terminal connected to each other in the network. And the second terminal for communicating data via the server, wherein (a) the first terminal and the second terminal respectively have an encryption key and a corresponding decryption key (B) one of the first terminal and the second terminal receives the encryption key generated by the other terminal from the other terminal, and (c) The one terminal encrypts the data with the received encryption key; (d) the one terminal sends the encrypted data to the other terminal; and (e) the other terminal. The terminal is encrypted Upon receipt of the data, characterized in that it comprises a step of decoding the data received using said decryption key terminal of the other side is produced, the.

  Invention of Claim 2 created in order to solve the said subject WHEREIN: The data communication method of Claim 1 WHEREIN: The said step (c), (c1) The said one terminal produces | generates this one terminal Adding the encryption key to the data and then encrypting the data, wherein the step (e) includes (e1) when the other terminal decrypts the encrypted data Acquiring the encryption key generated by the terminal of the terminal, and the data communication method further comprises: (f) the other terminal encrypts the data with the acquired encryption key, and transmits the data to the one terminal. And (g) decrypting the received data using the decryption key generated by the one terminal when the one terminal receives the encrypted data. And butterflies.

  Invention of Claim 3 created in order to solve the said subject is the data communication method of Claim 2, Said step (f), (f1) Said other terminal respond | corresponds to an encryption key and it A new generation of a decryption key; and (f2) the other terminal encrypts the data after adding the encryption key newly generated by the other terminal to the data. The step (g) includes the step (g1) of acquiring the encryption key generated by the other terminal when the one terminal decrypts the encrypted data; (H) a step in which the one terminal newly generates an encryption key and a corresponding decryption key; and (i) a step in which the step (h) is repeated a predetermined number of times from the step (c). The And wherein the Mukoto.

    Invention of Claim 4 created in order to solve the said subject is the data communication method as described in any one of Claim 1 thru | or 3. WHEREIN: Before said step (a), (j1) said one of The terminal further includes a step of generating communication permission request data and sending the communication permission request data to the other terminal. (J2) Between the steps (a) and (b), (j2) When communication permission request data is received, communication permission request response data corresponding to the communication permission request data is generated, and the encryption key generated by the other terminal in step (a) is added to the communication permission request response data. And sending the data to the one terminal.

  Invention of Claim 5 created in order to solve the said subject WHEREIN: In the data communication method of Claim 4, before the said step (j1), (j3) The said 1st terminal and the said 2nd A terminal newly generating an encryption key and a corresponding decryption key; and (j4) the first terminal and the second terminal respectively send the generated encryption key to the server; And (j5) after the step (j1), when the server receives the communication permission request data from the one terminal, the server holds the data in the data. Adding the encryption key generated by the one terminal, and further encrypting the data with the encryption key generated by the other terminal and then transferring the data to the other terminal. In the step (j2), the other terminal decrypts the communication permission request data with the decryption key generated by the other terminal to obtain the encryption key generated by the one terminal, The communication permission request response data and the encryption key added to the data are encrypted with an encryption key, and the encryption key received by the one terminal in the step (b) includes the communication permission response data in the step (b). It is obtained by decrypting with the decryption key generated by the one terminal in a).

  Invention of Claim 6 created in order to solve the said subject WHEREIN: The data communication method of Claim 4 or 5 WHEREIN: The said communication permission request data contains the user ID of a transmission source, In said step (j2) The other terminal determines a destination of the communication permission request response data by referring to the user ID of the transmission source included in the communication permission request data.

  Invention of Claim 7 created in order to solve the said subject WHEREIN: In the data communication method of Claim 6, the said 1st terminal and the said 2nd terminal each store the user ID of the terminal which can communicate In the step (j2), when the other terminal collates the user ID of the transmission source included in the communication permission request data with the user ID stored in the terminal, it matches The communication permission request response data for permitting communication is generated, and the communication permission request response data for rejecting communication when there is no match is generated.

  The invention of claim 8 devised to solve the above problem is the data communication method according to any one of claims 1 to 7, wherein the encryption key and the decryption key have a predetermined usable period. Further, when the usable period expires, the encryption process and the decryption process become impossible.

  Invention of Claim 9 created in order to solve the said subject is a program which makes a computer perform the data communication method as described in any one of Claim 1 thru | or 8.

  The invention of claim 10 created to solve the above-described problem is a computer-readable medium storing the program according to claim 9.

  Invention of Claim 11 created in order to solve the said subject, the interconnected server which performs the data communication method as described in any one of Claim 1 thru | or 8, the 1st terminal, A network system comprising a second terminal, wherein the first terminal and the second terminal include a plurality of encryption keys and a plurality of decryption keys corresponding to the encryption keys; Communication means for transmitting / receiving an encryption key and the data, encryption processing means for encrypting the data to be transmitted using the encryption key, and decryption of the encrypted data using the decryption key And a decryption processing means.

  Invention of Claim 12 created in order to solve the said subject WHEREIN: The network system of Claim 11 WHEREIN: The said 1st terminal and the said 2nd terminal are the information of the user ID of the terminal which can communicate. It further includes: an ID storage unit including communication communication request unit that generates communication permission request data including a transmission source user ID and communication permission request response data in response to the request data.

  Invention of Claim 13 created in order to solve the said subject WHEREIN: The network system of Claim 11 or 12 WHEREIN: The decoding key management means which manages the said encryption key and the said decryption key based on elapsed time is provided. In addition, the encryption key and the decryption key are disabled when a predetermined time elapses after the encryption key and the decryption key are generated.

  Invention of Claim 14 created in order to solve the said subject is the said 1st and 2nd terminal of the network system as described in any one of Claim 11 thru | or 13.

  The data communication method according to claim 1, wherein a terminal that performs communication receives an encryption key from a partner terminal that communicates, encrypts the data with the received encryption key, and sends the encrypted data to the partner terminal It has become. Then, the terminal that has received the data decrypts the data with the decryption key generated at the same time as the encryption key. The decryption key is always held in the generated terminal and is not sent to the outside. Therefore, it is unlikely that the decryption key is transferred to a third party and the content of data communicated using this decryption key is read. In addition, since the exchange of the encryption key is performed via the network, the convenience of data communication is not impaired by the exchange operation, and no additional cost associated with the exchange occurs.

  In the data communication method according to claims 2 and 3, when data is communicated between terminals, the data is always encrypted using a new encryption key. Therefore, even if one encryption key is transferred to a third party and the encrypted format is decrypted and the data content is read, the subsequent data is read in the same way because the encrypted format is different. I can't. Therefore, it is unlikely that all of the communicated data is read by a third party.

In the data communication method according to claims 4 to 7, a process of authenticating the communication partner is performed before performing the data communication. Prior to this authentication process, each terminal needs to register its own user ID in another terminal. Thereby, even if a terminal other than a regular terminal, that is, a terminal whose user ID is not registered requests communication from a regular terminal, the request is not authenticated.
The server also manages the user ID in association with the terminal, and recognizes the terminal corresponding to the user ID as a regular terminal. Furthermore, the data is transferred only to the legitimate terminal with reference to the user ID given to the data. Here, the communication permission request response data informing whether communication authentication is possible is sent to the user ID of the transmission source terminal added to the communication permission request data. Therefore, even if a third party terminal generates the same data as the communication permission request data generated by a certain legitimate terminal and impersonates the legitimate terminal and requests communication from another legitimate terminal, The communication permission request response data for authenticating the communication is not returned to the third party terminal but sent to the spoofed regular terminal. Therefore, it is difficult for a third party terminal to perform communication by impersonating a regular terminal.

  Further, prior to this authentication process, each terminal generates a key pair and submits the encryption key to the server. The server receives this and holds it in association with the user ID of the terminal. Thereafter, when communication permission request data addressed to another terminal is received from a terminal with a server, an encryption key already received from the terminal of the data transmission source is added to the data, and further the destination of the data The data is transferred to the destination terminal after encryption using the encryption key already received from the terminal.

When a third-party terminal impersonates a legitimate terminal and sends communication permission request data to a specific legitimate terminal, the server appends the impersonated legitimate terminal encryption key to that data, and Transfer to a legitimate terminal. The regular terminal of the destination obtains the encryption key from the received data, encrypts the communication permission request response data with the encryption key, and sends it to the server. The server then forwards this data to the authorized regular terminal. In this communication path, even if a third-party terminal sniffs the communication permission request response data, it cannot read the data because it does not have a decryption key for decrypting the encrypted data. Therefore, the communication between the third party terminal and the legitimate terminal ends at that time. Therefore, it is difficult for a third party terminal to impersonate a legitimate terminal.
On the other hand, when a third party impersonates a server, encrypts the communication permission request data with the encryption key created by itself, and sends it directly to a legitimate terminal, the legitimate terminal corresponds to the encryption key. Since it does not have a decryption key, the communication permission request data cannot be read. Therefore, the communication process ends at that time, and no communication is performed between the third party terminal and the legitimate terminal.
Therefore, the data communication methods of claims 4 to 7 make it virtually impossible for a third party terminal to impersonate a legitimate terminal.

  The data communication method according to claim 8 is configured such that an expiration date is provided for the encryption key and the decryption key, and the encryption key and the decryption key cannot be used after the expiration date. Therefore, even if the decryption key is in the hands of a third party, the data cannot be read unless the third party decrypts the data within the expiration date. Therefore, it is possible to reduce the possibility of data eavesdropping by appropriately setting the expiration date of the decryption key. Furthermore, by appropriately setting the expiration date of the encryption key, it is possible to refuse communication with a terminal that has permitted communication in the authentication process from a certain point in time.

  The program according to claim 9 allows an arbitrary computer to execute the data communication method.

  The computer-readable medium according to claim 10 can suitably provide the above-described data communication method to the user.

  The network system according to claims 11 to 13 can provide a system for executing the data communication method.

  According to the first terminal and the second terminal of the fourteenth aspect, it is possible to provide a terminal constituting a system for executing the data communication method.

  According to the present invention, it is possible to realize data communication in which a key can be safely sent via a network and a key pair can be easily changed. In addition, since the communication method of the present invention prevents wiretapping and spoofing of data by a third party, a network system having strong security can be constructed by using the communication method of the present invention.

A communication network system according to a preferred embodiment of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a communication network system 100 for communicating data encrypted using a public key according to an embodiment of the present invention. As shown in this figure, the communication network system 100 includes a server 10, a first terminal 20, a second terminal 30, and a network 40. In addition, although this figure has each shown four 1st terminals 20 and 2nd terminals 30, the number of these terminals is not specifically limited, You may use arbitrary numbers of terminals.

  The server 10 is a device that mediates communication of data performed between the first terminal 20 and the second terminal 30, and is configured by an existing computer or the like, and encrypts data as will be described in detail later. An encryption processing unit. Furthermore, the server 10 performs the role of authenticating and identifying each terminal connected to the network and guaranteeing the contents of the encryption key and data exchanged between the terminals. The first terminal 20 is a device for performing data communication with the second terminal 30, and includes an existing communication device such as a computer, a portable terminal (such as a PDA), and a cellular phone. On the other hand, the second terminal 30 is a device for performing data communication with the first terminal 20, and is configured from existing communication equipment in the same manner as the first terminal 20. The network 40 enables data communication between both terminals by connecting the server 10 and the first terminal 20 and between the server 10 and the second terminal 30. The network 40 includes an existing network such as the Internet, Ethernet (registered trademark), and wide area Ethernet. The network 40 is directly connected to each device, or indirectly connected via a wired and / or wireless communication line.

[Function of first terminal 20 (second terminal 30)]
With reference to FIG. 2, the function of the terminal which comprises the communication network system 100 is demonstrated below. In the present embodiment, the first terminal 20 and the second terminal 30 have the same function and structure. Therefore, only the first terminal 20 will be described, and the description of the second terminal 30 will be omitted.
The first terminal 20 includes, as its functional elements, a control unit 110, a data holding unit 120, an ID storage unit 130, an authentication unit 140, a key generation unit 150, a key storage unit 160, and an encryption processing unit. 170, a decryption processing unit 180, a communication processing unit 190, and a key management unit 200.
The functional elements 130 to 200 are controlled by the control unit 110 and access the data holding unit 120 as necessary. All functional elements are implemented by an arithmetic device such as a processor (CPU) and a storage device such as a memory and a hard disk.

[ID storage unit]
The ID storage unit 130 is a functional element for registering a user ID of a terminal capable of communication, and this user ID is used in a step of authenticating a communication request from another terminal. The user ID is composed of a code of several bits and the like, and is uniquely given to each of the first terminal 20 and the second terminal 30. When each terminal communicates on the communication network system 10, it is necessary to register the user ID of the other party to communicate in advance in its own ID storage unit 130.

[Authentication part]
The authentication unit 140 is a functional element used in the process of authenticating communication with other terminals. When the first terminal 20 communicates with the second terminal 30, the authentication unit 140 of the first terminal 20 generates “communication permission request data” and sends it to the second terminal 30 via the server 10. This communication permission request data includes the user ID of the transmission source terminal and the encryption key generated by the transmission source terminal.
On the other hand, when the second terminal 30 receives the communication permission request data from the first terminal 20 via the server 10, the authentication unit 140 of the second terminal 30 generates “communication permission request response data”. It is sent to the first terminal 20 via the server 10. Specifically, in the second terminal 30, the authentication unit 140 accesses the ID storage unit 130 and confirms whether or not the user ID included in the received communication permission request data is registered in the ID storage unit 130. . When the same user ID is registered in the ID storage unit 130, the authentication unit 140 generates communication permission request response data indicating that communication is permitted, and when not registered, the communication is rejected. Communication permission request response data is generated.

[Key generator]
The key generation unit 150 is a functional element that generates an encryption key for encrypting data and a decryption key for decrypting data encrypted with the encryption key. After generating these key pairs, the key generation unit 150 sends the encryption key to the communication processing unit 190 and the decryption key to the key storage unit 160. The key generation unit 150 always generates a key pair having different information, and the encryption key is associated with the user ID of the generation source terminal so that it can be identified for which terminal. Furthermore, the generated time information is associated with the encryption key and the decryption key.

[Key storage unit]
The key storage unit 160 is a functional element for storing the encryption key received from the other terminal by the communication processing unit 190 and the decryption key generated by the key generation unit 150.

[Encryption processor]
The encryption processing unit 170 is a functional element that encrypts data to be transmitted in a predetermined encryption format using the encryption key received by the communication processing unit 190 and stored in the key storage unit 160. As the encryption format of the present embodiment, an existing encryption format (for example, RSA) in the technical field may be used.

[Decryption processing unit]
The decryption processing unit 180 is a functional element that decrypts data and the like generated by the key generation unit 150 and stored using the decryption key stored in the key storage unit 160.

[Communication processor]
The communication processing unit 190 is a functional element that exchanges data, encryption keys, and the like with a communication partner. The structure of data to be communicated will be described later.

[Key Management Department]
The key management unit 200 is a functional element that manages the expiration date of the encryption key and the decryption key, refers to the generation time associated with each key, and sets a predetermined period (for example, 24) after the key is generated. Check if time has passed.

A method in which the first terminal 20 and the second terminal 30 having the above functions communicate data via the server 10 via the network 40 will be described with reference to FIGS.
In the following description, a procedure when the first terminal 20 requests communication permission from the second terminal 30 will be described as an example. However, the second terminal 30 requests communication permission from the first terminal 20. Is also possible. Of course, it is also possible to request communication permission between the first terminals 20 or between the second terminals 30.

FIG. 3 shows the procedures of the first terminal 20, the server 10, and the second terminal 30 associated with data communication in time series. In the figure, [A1] to [A12] are procedures performed by the first terminal 20, [B1] to [B6] are procedures performed by the server 10, and [C1] to [C16] are procedures performed by the second terminal 30. Shows the procedure to be performed. The number of the key pair generated by the first terminal 20 is 1a to 1n (n is a positive integer), and the number of the key pair generated by the second terminal 30 is 2a to 2n.
FIG. 4 shows the structure of data that is actually communicated.
First, the first terminal 20 generates a 1a key pair ([A1] in FIG. 3). Then, the 1a encryption key of the generated key pair is sent to the server 10 ([A2]), and the 1a decryption key is held by itself ([A3]). The server 10 that has received the 1a encryption key associates the 1a encryption key with the terminal ID of the sender, and holds it ([B1]).
It is preferable that the above procedure is not performed immediately before performing communication, but is performed in advance when the terminal is activated.

  Similarly, the second terminal 30 generates the 2a key pair ([C1]). Then, the 2a encryption key of the generated key pair is sent to the server 10 ([C2]), and the 2a decryption key is held by itself ([C3]). The server 10 that has received the 2a encryption key associates the 2a encryption key with the terminal ID of the sender, and holds it ([B2]). The above procedure is also preferably performed in advance when the terminal is started.

Next, the first terminal 20 sends communication permission request data to the server 10 in order to request communication permission from the second terminal 30 ([A4]).
The communication permission request data used at this time has a structure shown in FIG. Specifically, the user ID (hereinafter referred to as the transmission destination terminal ID) of the transmission destination (second terminal 30), the user ID (hereinafter referred to as the transmission source terminal ID) of the transmission source (first terminal 20), and this And a type indicating that the data is a transmission permission request.

Upon receiving the communication permission request data, the server 10 adds the 1a encryption key held in the procedure [B1] to the communication permission request data, and further encrypts it with the 2a encryption key held in the procedure [B2]. The encrypted communication permission request data is sent to the second terminal 30 ([B3]). At this time, the server 10 searches for the encryption key of the 1a that is the corresponding encryption key based on the transmission source terminal ID included in the communication permission request data. If the server 10 does not hold the corresponding encryption key at this time, the server 10 reports that there is no encryption key corresponding to the first terminal 10 and stops the subsequent processing.
The communication permission request data transferred from the server 10 to the second terminal 30 has a structure shown in FIG. Here, the server 10 recognizes the transfer destination as the third terminal 30 by referring to the transmission destination terminal ID of the received communication permission request data (FIG. 4A).

When the second terminal 30 receives the communication permission request data from the server 10, the second terminal 30 decrypts the data using the decryption key 2a held by itself ([C4]), and obtains the 1a encryption key from the decrypted data. Obtain ([C5]). Details of the decryption process will be described later. The second terminal 30 recognizes that the permission of communication is requested from the first terminal 20 by referring to the type of the decrypted data and the transmission source ID, and thereafter performs the authentication process ([[ C6]). Details of this authentication process will be described later.
After the authentication process, the second terminal 30 generates the 2b key pair ([C7]). Then, the 2b encryption key of the 2b key pair is added to the communication permission request response data generated by the authentication process, and these are encrypted using the 1a encryption key obtained in the procedure [C5]. ([C8]). Next, the encrypted communication permission request response data is sent to the server 10 ([C9]). Note that the second terminal 30 holds the decryption key 2b as it is ([C10]).

  The structure of the communication permission request response data at this time is shown in FIG. The communication permission request response data includes information for permitting or denying communication. In the present embodiment, the description is continued on the assumption that communication is permitted here. However, if communication is rejected, the second terminal 30 omits the steps [C7] and [C8]. Good.

  When the server 10 receives the communication permission request response data (FIG. 4C), the communication permission request response data is transferred to the first terminal 20 with reference to the destination terminal ID of this data ([B4]). . The data structure at that time is shown in FIG.

When the first terminal 20 receives the communication permission request response data (FIG. 4 (d)), it decrypts the received data using the decryption key 1a held by itself ([A5]) and decrypts the data. The 2b encryption key is obtained from the data ([A6]).
The above procedure is mainly performed for the purpose of reliably delivering the first encryption key to the communication partner and preventing impersonation by a third party terminal that is not a legitimate terminal (see paragraph 0026 for details). .
Next, the first terminal 20 generates the 1b key pair ([A7]).
When the 1b key pair is generated, the 1b encryption key of the 1b key pair is added to the data (first data) to be sent to the second terminal 30, and the 1st key pair obtained in step [A6] is obtained. Data is encrypted with the encryption key 2b ([A8]). Then, the encrypted first data is sent to the server 10 ([A9]), and the 1b decryption key is held as it is ([A10]). The structure of this first data is shown in FIG.
However, if the received communication permission request response data includes information for refusing communication, all subsequent processes are stopped without performing steps [A6] to [A10].

  Upon receiving the first data (FIG. 4E), the server 10 sends this data to the second terminal 30 ([B5]). The structure of this data is shown in FIG.

When the second terminal 30 receives the first data (FIG. 4F) from the server 10, the second terminal 30 decrypts the data received with the decryption key 2b held by itself ([C11]). Next, the 1b encryption key is obtained from the decrypted data ([C12]).
Subsequently, a 2c key pair is generated ([C13]), and the 2c encryption key of the key pair is added to data (second data) to be sent to the first terminal 20, and the procedure [C12 ] Are encrypted with the 1b encryption key obtained in [1] ([C14]) and sent to the server 10 ([C15]). The 2c decryption key is held as it is (C16). The structure of the data sent at this time is shown in FIG.

  When the server 10 receives the second data shown in FIG. 4G, the server 10 changes the data to the structure shown in FIG. 4H and sends the data to the first terminal 20 ([B6]).

  Upon receiving the second data (FIG. 4H), the first terminal 20 decrypts the second data with the 1b decryption key held by itself ([A11]). Then, the second c encryption key is acquired ([A12]).

  The above is the procedure in which the first terminal 20 and the second terminal 30 communicate data via the server 10 via the network 40. Procedures [A7] to [A12] are performed a predetermined number of times as necessary. You can repeat it. However, in that case, since the encryption format of the encryption key may be deciphered by a third party, it is preferable to always create different key pairs.

Next, authentication processing ([C6] in FIG. 4) performed by the second terminal 30 in the present embodiment will be described in detail with reference to the flowchart in FIG.

First, the second terminal 30 receives communication permission request data from the first terminal 20 via the server 10 (step S1). Next, the second terminal 30 refers to the transmission source terminal ID of this communication permission request data. Then, the authentication unit 140 of the second terminal 30 accesses the ID storage unit 130, and confirms whether or not the same user ID as this transmission source terminal ID is registered (step S2).
If the same user ID is registered in the ID storage unit 130 (“YES” in step S2), the second terminal 30 generates communication permission request response data indicating permission of communication. Then, this data is sent to the transmission source terminal ID (first terminal 20) (step S3). Alternatively, if the same user ID is not registered (“NO” in step S2), the second terminal 30 generates communication permission request response data indicating that communication is denied, This data is sent to the ID (first terminal 20) (step S4).

  In the above procedure, when the second terminal 30 sends the communication permission request response data, it corresponds to the transmission source ID included in the communication permission request data, not the terminal that actually sent the communication permission request data. It is configured to send to the terminal. Therefore, even if the third terminal that is not a legitimate terminal impersonates the first terminal 20 and sends the communication permission request data shown in FIG. 4A to the second terminal 30, FIG. Is transmitted to the first terminal 20 instead of the third terminal. Therefore, the act of impersonation by the third terminal is prevented in advance.

  Next, the decoding process ([C4], [A5], [C11], [A11] in FIG. 3) performed by each terminal will be described with reference to FIG. FIG. 6 shows a flowchart of the decoding process.

First, the destination terminal receives encrypted data from the source terminal (step S5).
Next, the transmission destination terminal checks whether or not a decryption key capable of decrypting the encrypted data is stored in its own key storage unit 160 (step S6).
If the corresponding decryption key is not stored (“NO” in step S6), the subsequent processing is terminated. When the corresponding decryption key is stored ("YES" in step S6), the key management unit 200 refers to the generation date associated with the decryption key and the predetermined decryption key is set in advance. It is confirmed whether or not the time limit has passed (step S7).
If the predetermined time limit has not passed ("YES" in step S7), the encrypted data is decrypted using the decryption key (step S8). Alternatively, when the corresponding decryption key has passed the predetermined time limit (“NO” in step S7), the subsequent processing is terminated.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various other changes and modifications can be made.
For example, in the present embodiment, when the first terminal 20 and the second terminal 30 respectively pass the 1a encryption key and the 2a encryption key to the server 10 (procedures [A2] and [C2] in FIG. 3). ), The encryption key is sent via the network, but the present invention is not limited to this. Alternatively, the first and second terminals 20 and 30 pass the URL and authentication password of a predetermined site to the server 10 in advance, the server accesses the site of those URLs, and further receives the received authentication password. The encryption keys of the first and second a may be downloaded and obtained from the site. If this method is adopted, there is a low possibility that an encryption key is wiretapped by a third party, and a system and method capable of realizing stronger security can be provided.

  In the present embodiment, the first terminal 20 and the second terminal 30 generate a new and different key pair each time data is sent, but this generation process is not particularly limited and may be an alternative. First, a key pair may be generated only once, and then this key pair may be used repeatedly. Alternatively, a new key pair may be generated every time data is sent twice, three times,... N times. In general, a network system with higher security can be constructed by always generating and using different key pairs. However, on the other hand, the processing becomes complicated, and the communication speed is delayed by the time required for it. Therefore, it is preferable to determine the key pair generation frequency in consideration of the security level and communication speed required for the communication system to be used.

  In this embodiment, the authentication process for communication permission is performed only once at the beginning. However, the timing of this authentication process is not particularly limited, and may be performed every time data is communicated instead. Alternatively, the authentication process may be performed every time data is communicated twice, three times, ... n times. In this case as well, it is preferable that the frequency of performing the authentication process is determined based on the required specifications of the communication system to be used, as in the generation of the key pair.

  In the present embodiment, the first terminal 20 and the second terminal 30 generate a key pair immediately before data transmission. However, the generation timing of the key pair is not particularly limited, and may be an alternative. Alternatively, a plurality of key pairs may be generated in advance (for example, at the time of activation) and stored in its own key storage unit 160. By generating the key pair in advance, the time for generating the key pair during communication can be omitted.

  The method for setting the expiration date for the encryption key and the decryption key in this embodiment is not particularly limited, and the expiration date may be uniformly set to a predetermined period, or may be set individually for each key. Also good. For example, the degree of importance may be given to the data to be sent in stages, and the expiration date may be set earlier for data with a higher degree of importance. Alternatively, each terminal may set an arbitrary period every time data is sent. In this case, in addition to the generated time information, the expiration date information is associated with each key.

  In this embodiment, an example in which the present invention is applied to a public key communication system has been described. However, the present invention is not limited to this, and is preferably applied to a communication system employing a common key method. Is possible. In that case, instead of generating a key pair, the first terminal 20 and the second terminal 30 may generate a common key and a copy thereof and exchange the copy key.

  The communication method according to the embodiment of the present invention described above is preferably implemented as a program. In that case, the program is preferably downloaded from an external server or the like to a terminal that executes the method, or distributed in the form of a computer-readable medium. Examples of the computer-readable medium include a CD-ROM, a magnetic tape, a flexible disk, and an optical data storage device.

  As a modification of the present embodiment, some of the functions of the first terminal 20 and the second terminal 30 shown in FIG. FIG. 10 shows a communication network system 1000 according to a modification of the embodiment of the present invention.

  The communication network system 1000 includes four first terminals 200, four second terminals 600, a first server 300, a second server 500, two internal networks 700, and an external network 400. Is provided. Further, the first terminal 200, the first server 300, and the internal network 700 constitute an internal network of the first organization 800. Similarly, the second terminal 600, the second server 500, and the internal network 700 constitute the internal network of the second group 900. The organization 800 and the organization 900 are interconnected by the external network 400.

  The “first and second organizations” in this modification represent one aggregate created by a specific member such as a company or an organization.

  In this system, the first terminal 200 is used only for members of the first organization 800. Similarly, the second terminal 600 is used only for members of the organization 900. Therefore, it can be determined that the first terminal 200 and the second terminal 600 of the communication network system 1000 are not likely to be used by a malicious third party. Therefore, it is not necessary to take any security measures for data exchanged in the internal network 700 of the first organization 800 and the second organization 900. Only the data exchanged between the first server 300 and the second server 500 via the external network 400 requires security measures. Therefore, it is only necessary to configure the system so as to encrypt only the data communicated between these servers.

  FIG. 8 shows a configuration of internal functions of the first / second terminal (200 or 600) and the first / second server (300 or 500) in FIG. According to this figure, each terminal 200/600 has only the communication processing unit 1200 as functional elements, and the ID storage unit 1130, the authentication unit 1140, the key generation unit 1150, and the key, which are other functional elements. The storage unit 1160, the encryption processing unit 1170, the decryption processing unit 1180, and the key management unit 1900 are implemented by the server 300/500.

  As described above, since only the data communicated between the servers 300 and 500 needs to be encrypted, the server 300/500 can be configured to have all functions necessary for encryption and decryption. In this system, each server collectively manages encryption and decryption processing. However, in the communication network system 100 of FIG. 1, since each terminal independently generates and manages a key pair, the same key may be used between the terminals. On the other hand, in the communication network system of FIG. 8, since each server can uniquely generate and manage a key pair, each terminal does not generate and use the same key pair. Therefore, in this modification, a communication network system having stronger security is constructed. In addition, since the servers 300 and 500 collectively perform encryption and decryption processing, a communication network system is preferably constructed even when the first terminal 200 and the second terminal 600 to be used have low computing capabilities. Can do.

  As mentioned above, although this invention was demonstrated using embodiment shown in drawing, these are only an illustration and those skilled in this technical field can variously be within the range which does not deviate from the range and the meaning of this invention. It will be understood that modifications and variations are possible. Accordingly, the scope of the invention should not be determined by the described embodiments, but by the technical spirit described in the claims.

1 is a diagram illustrating a configuration of a communication network system 100 according to an embodiment of the present invention. 2 is a block diagram showing functions of the first terminal 20 or the second terminal 30 of the communication network system 100. FIG. 2 is a flowchart showing a communication method performed by the communication network system 100. FIG. (A) to (h) are diagrams showing the structure of data generated and exchanged by the communication network system 100. FIG. 3 is a flowchart showing details of authentication processing performed by the communication network system 100. 4 is a flowchart showing details of a decoding process performed by the communication network system 100. It is a figure which shows the structure of the communication network system 1000 which concerns on the modification of 1 embodiment of this invention. 2 is a block diagram illustrating functions of a first terminal 200 and a first server 300 or a second terminal 600 and a second server 500 of the communication network system 1000. FIG.

Explanation of symbols

10 server 20 first terminal 30 second terminal 40 network 100 communication network system 110 control unit 120 data holding unit 130 ID storage unit 140 authentication unit 150 key generation unit 160 key storage unit 170 encryption processing unit 180 decryption processing unit 190 Communication processing unit 200 Key management unit

Claims (14)

Data is transmitted between the first terminal and the second terminal via the server in a communication network system including a server, a first terminal, and a second terminal connected to each other via a network. Communication method,
(A) the first terminal and the second terminal each generating an encryption key and a corresponding decryption key;
(B) one of the first terminal and the second terminal receives an encryption key generated by the other terminal from the other terminal;
(C) the one terminal encrypts data with the received encryption key;
(D) the one terminal sends the encrypted data to the other terminal;
(E) when the other terminal receives the encrypted data, decrypting the received data using a decryption key generated by the other terminal;
A data communication method comprising: The step (c)
(C1) the one terminal includes the step of encrypting the data after adding the encryption key generated by the one terminal to the data;
The step (e)
(E1) including a step of acquiring an encryption key generated by the one terminal when the other terminal decrypts the encrypted data;
further,
(F) the other terminal encrypts data with the acquired encryption key and sends the data to the one terminal;
(G) when the one terminal receives the encrypted data, decrypting the received data using the decryption key generated by the one terminal;
The data communication method according to claim 1, further comprising: The step (f)
(F1) the other terminal newly generates an encryption key and a corresponding decryption key;
(F2) the other terminal encrypts the data after adding the encryption key newly generated by the other terminal to the data,
The step (g)
(G1) including the step of obtaining the encryption key generated by the other terminal when the one terminal decrypts the encrypted data;
further,
(H) the one terminal newly generating an encryption key and a corresponding decryption key;
(I) repeating the step (h) from the step (c) a predetermined number of times;
The data communication method according to claim 2, further comprising: Before step (a),
(J1) further comprising the step of the one terminal generating communication permission request data and sending the communication permission request data to the other terminal;
Between the steps (a) and (b),
(J2) When the other terminal receives the communication permission request data, it generates communication permission request response data corresponding to the communication permission request data, and adds the other communication permission request response data to the communication permission request response data in the step (a). 4. The data communication method according to claim 1, further comprising a step of adding the encryption key generated by the terminal and sending the data to the one terminal. Before step (j1)
(J3) the first terminal and the second terminal each newly generating an encryption key and a corresponding decryption key;
(J4) the first terminal and the second terminal each send the generated encryption key to the server, and the server holds the encryption key;
After the step (j1),
(J5) When the server receives the communication permission request data from the one terminal, the encryption key generated by the one terminal held by the server is added to the data, and the data is further transferred to the other terminal. Further comprising the step of transferring to the other terminal after encrypting with the encryption key generated by
In the step (j2),
The other terminal decrypts the communication permission request data with the decryption key generated by the other terminal, acquires the encryption key generated by the one terminal, and uses the encryption key to transmit the communication permission request response. Data and the encryption key added to the data are encrypted, and the encryption key received by the one terminal in the step (b) is the communication permission response data, and the one terminal is the step (a). 5. The data communication method according to claim 4, wherein the data communication method is obtained by decrypting with the generated decryption key. The communication permission request data includes a transmission source user ID,
In the step (j2), the other terminal determines a destination of the communication permission request response data by referring to the user ID of the transmission source included in the communication permission request data. The data communication method according to claim 4 or 5. The first terminal and the second terminal each store a user ID of a communicable terminal,
In the step (j2), the other terminal compares the user ID of the transmission source included in the communication permission request data with the user ID stored in itself and permits communication when they match. 7. The data communication method according to claim 6, wherein the communication permission request response data indicating that communication is to be generated and the communication permission request response data indicating that communication is rejected if they do not match are generated.   8. The encryption key and the decryption key have a predetermined usable period, and after the usable period expires, the encryption process and the decryption process become impossible. The data communication method described in 1.   The program which makes a computer perform the data communication method as described in any one of Claims 1 thru | or 8.   A computer readable medium storing the program according to claim 9. A network system comprising an interconnected server, a first terminal, and a second terminal for executing the data communication method according to any one of claims 1 to 8,
The first terminal and the second terminal are:
Key generation means for generating a plurality of encryption keys and a plurality of decryption keys corresponding to the encryption keys;
Communication means for transmitting and receiving the encryption key and the data;
An encryption processing means for encrypting the data to be transmitted using the encryption key;
Decryption processing means for decrypting the encrypted data using the decryption key;
A network system comprising:   The first terminal and the second terminal include ID storage means including user ID information of a communicable terminal, communication permission request data including a transmission source user ID, and communication in response to the request data. The network system according to claim 11, further comprising communication authentication means for generating permission request response data.   Decryption key management means for managing the encryption key and the decryption key based on an elapsed time is further provided, and the encryption key and the decryption key cannot be used when a predetermined time elapses after the encryption key and the decryption key are generated The network system according to claim 11, wherein the network system is configured as follows.   The first and second terminals of the network system according to any one of claims 11 to 13.