KR20070061892A - Data communication method - Google Patents

Abstract

A data communication method capable of executing a synchronizing process at two or more computer terminals while ensuring security. A server certificate and a public key are transmitted through a host side terminal to a guest side terminal. This guest side terminal authenticates the server and encrypts a guest side hash key to be used in a hash function and the hash function with the public key. A web server decrypts the hash key and the hash function, and then creates a digest of the contents with the guest side hash key and transmits the digest through the host side terminal to the guest side terminal. The guest side terminal receives the contents received from the host side terminal and that digest, and compares that digest and a digest created from the received contents thereby to ensure the security when the synchronizing process is executed.

Description

Data communication method {DATA COMMUNICATION METHOD}

The present invention relates to a data communication method capable of executing synchronous processing while ensuring security when at least two or more computer terminals use a synchronous program for displaying the same screen.

When secured data communication is performed between a server and a computer terminal, a data communication method called SSL (Secure Socket Layer) as described in Non-Patent Document 1 is used. In this data communication method using SSL, since data can be transmitted and received between the server and the computer terminal, and data communication can be performed after the server is authenticated, convenience is high and it is the current standard technology.

On the other hand, a synchronization program for displaying content such as text or an image displayed in a web browser or the like in synchronization between a plurality of computer terminals exists as disclosed in Patent Documents 1 and 2 below.

In the synchronous program disclosed in Patent Literature 1, the computer terminal on the host side acquires the content from the web server through the session server, displays the content on the host terminal, and the computer terminal on the guest side displays the acquired content. By acquiring from the computer terminal on the host side, the synchronization display of the content can be performed by the computer terminal on the host side and the guest side.

Patent Document 1: WO / 2004/070616

Non-Patent Document 1: Ministry of Internal Affairs, "Information Security Site for the People, 2003, Internet <URL: http: //www.soumu.go.jp/joho_tsusin/security/kiso/k01_ssl.htm>

<Start of invention>

Problems to be Solved by the Invention

In the case of performing data communication using the cryptographic communication protocol such as SSL described above, since data communication is assumed to be 1: 1, secure data communication can be performed between the web server and the computer terminal on the host side. There is a problem that the computer terminal on the guest side cannot authenticate the web server, and also cannot secure the security of data communication.

That is, when the synchronization program as disclosed in Patent Document 1 is used, all of the data transmission / reception with the web server is a computer terminal on the host side, and the computer terminal on the guest side is not recognized by the web server. The guest server cannot authenticate the web server, and security cannot be secured in data communication.

Means for solving the problem

Therefore, the present inventors, when performing synchronization display using a synchronization program as disclosed in Patent Document 1, that is, when performing synchronization display between a plurality of computer terminals, one of the computer terminals on behalf of the server to represent In the case of performing synchronous processing by transmitting and receiving data between two and transmitting the contents acquired from the representative computer terminal to another computer terminal, a data communication method capable of performing data communication while ensuring security is invented.

The invention of claim 1 is a data communication method when performing synchronization processing of content stored in a web server between a host terminal terminal capable of cryptographic communication via at least one session server and at least one guest terminal terminal. The terminal receives the server certificate and the public key from the web server, stores the server certificate and the public key, and transmits the server certificate and the public key to the guest terminal via the session server. Receive the server certificate and the public key from a terminal, authenticate the server certificate, create a guest-side hash key for creating a digest of the content, and convert the guest-side hash key and hash function into the public key. By encrypting the data and transmitting the encrypted data to the host terminal. The host side terminal authenticates the received server certificate, creates a host side common key for encrypting the content by a common key cryptography scheme, and publishes the host side common key and the common key cryptography scheme. Encrypting with a key, transmitting the encrypted guest-side hash key and the hash function received from the guest-side terminal to the web server, wherein the web server receives the host-side terminal, The encrypted host-side common key, the common-key cryptography method, the encrypted guest-side hash key, and the hash function are decrypted based on a secret key corresponding to the public key, and the content is decrypted by the guest. The digest is created by the hash function based on the side hash key, and the digest is generated. Based on the decrypted host-side common key, contents are encrypted using the common key cryptography method, and the encrypted ones are transmitted to the host-side terminal, and the host-side terminal transmits the encrypted digest and the content to the web. Receiving from the server, decrypting the encrypted digest and content using the created host-side common key, transmitting the decrypted digest and content to the guest-side terminal through the session server, and sending the content to the host. Displayed by the side terminal, the guest side terminal receives the decoded digest and content from the host side terminal, creates a digest from the received content based on the created guest side hash key and hash function, The digest and the received digest When compared to a match data communication method of displaying the contents in the guest-side terminal.

In this way, by transmitting the server certificate and the public key to the guest terminal through the host terminal, the guest terminal can authenticate the server. In addition, the guest-side hash key used by the guest terminal in the hash function and the hash function are encrypted by the public key, decrypted by the web server, and the web server digests the content with the guest-side hash key. And transmit it to the guest terminal through the host terminal, the guest terminal receives the content and the digest received from the host terminal, compares the digest with the digest created from the received content, Alteration in the middle of the communication path can also be detected.

By such a data communication method, conventionally, data communication with a 1: 1 security like SSL can be used as data communication with a 1: n security.

The invention of claim 2 is that the encrypted communication between the host terminal and the guest terminal is performed by performing encrypted communication between the host terminal and the session server, and the guest terminal and the session server, respectively. Way.

In the data communication between the host terminal and the guest terminal, the encrypted communication is performed at a ratio of 1: 1, respectively, so that communication between the host terminal and the guest terminal can be secured.

The invention according to claim 3 is characterized in that the synchronous process checks whether or not the user of the host-side terminal selects the content display request, thereby storing the content in the host-side terminal. The terminal displays the content and notifies the guest terminal terminal of a content update event through the session server, thereby transmitting the content corresponding to the content transmission request received from the guest terminal to the guest terminal. And, if the guest terminal receives the content, displays the content, and if the content is not stored, the web server transmits the content transmission request to the web server from the host terminal. The server certificate and public key A method of data communication that is initiated by the transmission.

According to the invention of claim 4, in the synchronous process, the user of the guest-side terminal selects the display request of the content to confirm whether the content is stored in the guest-side terminal, and if the memory is stored, the guest side. The terminal displays the content, notifies the host side terminal of the content update event through the session server, and displays the content stored in the host side terminal on the host side terminal. In the case of transmitting the content transmission request from the guest terminal to the host terminal, the host terminal receiving the content checks whether the content is stored in the host terminal, and the host terminal. If you remember from the above The content corresponding to the content transmission request received from the guest terminal by notifying the content updating event to the guest terminal through the session server and displaying the content at the guest terminal. The web server by transmitting the content transmission request from the host terminal to the web server if the content is displayed on the guest terminal and received and not stored in the host terminal. Is a data communication method initiated by transmitting the server certificate and a public key to the host terminal.

When performing content synchronization processing, even if a content transmission request is made from either the host terminal or the guest terminal, the host terminal may receive the content from the web server and transmit it to the guest terminal. This is because it is possible to reliably synchronize the content stored between the host terminal and the guest terminal.

The invention of claim 5 is a data communication system when performing synchronization processing of content stored in a web server between a host terminal terminal capable of cryptographic communication via at least one or more session servers and at least one guest terminal terminal. The web server includes public key / certificate transmitting means for transmitting a server certificate and a public key stored in a key / certificate storage means to the host terminal, and a host side created by the host terminal terminal and encrypted by the public key. A common key receiving means for receiving a common key, its encryption method, a guest-side hash key generated by the guest-side terminal and encrypted by the public key, and its hash function from the host-side terminal, and the encrypted host The common key, its encryption method, and the encrypted guest-side hash key and its hash function. Common key decrypting means for decrypting by a secret key stored in a key / certificate storing means, and server-side content storing means for storing the content of content corresponding to a content transmission request received by the web server from the host-side terminal. Extracts the content digest from the decrypted guest-side hash key and its hash function, and encrypts the generated digest and the content based on the decrypted host-side common key and its encryption scheme. And encrypting means for receiving the content transmission request from the host side terminal, and a server side content transmitting means for transmitting the digest and the content encrypted by the encrypting means to the host side terminal. And the server certificate from the web server A host-side public key / certificate receiving means for receiving the public key and storing it in a host-side public key / certificate storage means, and a public key / certificate transmitting means for transmitting the received server certificate and the public key to the guest terminal; Host-side key receiving means for receiving a guest-side hash key and its hash function generated by the guest-side terminal and encrypted by the public key, and encrypting the content by a common key cryptography method. Host-side common key generating means for creating a host-side common key to be used at the time and storing the host-side common key and its encryption method in a host-side common key storage means, and the created host-side common key and its encryption method. Common to the host side encrypted by the public key stored in the host-side public key / certificate storage means A host-side common key transmission for transmitting to the web server an encryption means, the encrypted host-side common key, its encryption method, and the encrypted guest-side hash key received from the host-side key receiving means and its hash function. Means, a host-side content receiving means for transmitting the content transmission request to the web server, receiving a digest and content encrypted by the host-side common key sent from the web server, and the received encrypted digest. Host-side content decrypting means for decrypting content with said host-side common key stored in said host-side common key storage means, and storing decrypted content in host-side content storage means, and said decrypted digest and content. Host side content transmitted to the guest terminal through a session server And a host-side content acquisition means for acquiring and displaying the content stored in the host-side content storage means. The guest terminal receives the server certificate and the public key from the host-side terminal. A guest-side public key / certificate receiving means which receives and stores in the guest-side public key / certificate storage means, and a guest-side hash key for creating a digest of the content by a hash function, and generates the guest hash key and The guest-side hash key generation means for storing the hash function in the guest-side hash key storage means, the created guest-side hash key and the hash function stored in the guest-side public key certificate storage means; Guest-side hash key encryption means for encrypting with a public key, and said encrypted guest-side Guest-side hash key transmitting means for transmitting a hash key and its hash function to the host-side terminal through the session server, guest-side digest receiving means for receiving the decoded digest from the host-side terminal, Guest-side content transmission / reception means for receiving the decoded content from a host-side terminal and storing it in a guest-side content storage means, and a guest-side hash key and its hash stored in the guest-side hash key storage means from the received content. When a digest is created based on a function, the created digest is compared with the digest received by the guest-side digest means, and if it matches, the guest-side digest comparison means for authenticating that the content is legitimate, and the authentic content is authenticated. Memory of the guest-side content A data communication system comprising guest-side content acquisition means for acquiring and displaying content stored in the means.

The data communication method described above can be realized as a data communication system by such a configuration.

The invention according to claim 6, wherein the web server performs synchronization processing of content stored in a web server between a host terminal terminal capable of cryptographic communication via at least one session server and at least one guest terminal terminal. As a data communication system to be used, the data communication system used in the web server includes public key / certificate transmitting means for transmitting a server certificate and a public key stored in a key / certificate storage means to the host terminal, A host-side common key created and encrypted by the public key, its encryption scheme, and a guest-side hash key and its hash function generated by the guest-side terminal and encrypted by the public key, from the host-side terminal; Common key receiving means, the encrypted host-side common key and its encryption method, Common key decryption means for decrypting the encrypted guest-side hash key and its hash function with a secret key stored in the public key / certificate storage means, and a content transmission request received by the web server from the host terminal. Is extracted from a server-side content storage means for storing the content, and a digest of the content is created based on the decoded guest-side hash key and its hash function, and the created digest and the content are generated. Encrypting means for encrypting based on the decrypted host-side common key and its encryption method, receiving a request for transmission of the content from the host-side terminal, and encrypting the digest and the content encrypted by the encrypting means to the host-side terminal. A server-side content transmitting means for transmitting, The host terminal decrypts the encrypted digest and the content received from the web server using the host-side common key generated by the host-side terminal, and decrypts the decrypted digest and the content to the guest-side terminal through the session server. While transmitting, the content is displayed on the host terminal, and the guest terminal receives the decoded digest and the content from the host terminal, based on the created guest-side hash key and hash function. A data communication system is used for creating a digest from the received content, comparing the digest with the received digest, and using the web server to display the content on the guest terminal.

The data communication system of the web server in the above-described data communication system may be configured as in the present invention.

According to the invention of claim 7, the host side terminal performs synchronization processing of content stored in a web server between a host side terminal capable of cryptographic communication via at least one or more session servers and at least one guest side terminal. A data communication system to be used, wherein the data communication system used in the host terminal includes: a host side public key / certificate receiving means for receiving a server certificate and the public key from the web server and storing them in a host-side public key / certificate storage means; Public key and certificate transmission means for transmitting the received server certificate and the public key to the guest terminal, a guest-side hash key generated by the guest terminal and encrypted by the public key, and a hash function thereof. Host-side key receiving means for receiving from the guest-side terminal; A host-side common key creating means for creating a host-side common key used when encrypting the existing content by a common key cryptography method, and storing the host-side common key and its cryptography method in a host-side common key storage means, and the created A host-side common key encryption means for encrypting a host-side common key and its encryption method by the public key stored in the host-side public key and certificate storage means, the encrypted host-side common key and its encryption method, A host-side common key transmitting means for transmitting the encrypted guest-side hash key and its hash function received by the host-side key receiving means to the web server, and sending a content transmission request to the web server, In the server, using the guest-side hash key and the hash function encrypted by the host-side common key. Host-side content receiving means for receiving the generated digest and its contents from the web server, and decrypting the received digest and content with the host-side common key for storing the received digest and content in the host-side common key storage means, and decrypting it. Host-side content decoding means for storing one content in a host-side content storage means, host-side content digest sending means for transmitting the decoded digest and content to the guest terminal through the session server, and the host-side content. And host-side content acquiring means for acquiring and displaying the content stored in the storage means, wherein the guest-side terminal receives the decoded digest and the content from the host-side terminal, and the created guest-side hash key and the Based on the hash function, A data communication system which creates the digest from the received content, compares the digest with the received digest, and matches the content with the host terminal to display the content on the guest terminal.

What is necessary is just to comprise the data communication system of the host side terminal in the above-mentioned data communication system like this invention.

Effect of the Invention

According to the present invention, even when synchronous processing is performed between a plurality of computer terminals, it is possible to execute data communication with security after authenticating that the web server is a legitimate server.

1 is a diagram showing an outline of an entire system configuration.

2 is a system configuration diagram showing an example of a system configuration of a web server.

3 is a system configuration diagram showing an example of a system configuration of a host-side terminal.

4 is a system configuration diagram showing an example of a system configuration of a guest terminal.

5 is a diagram illustrating an outline of a processing process using each key in the case of executing synchronous processing.

Fig. 6 is a flowchart showing a detailed processing process when a content transmission request is made from a host side terminal.

Fig. 7 is a flowchart showing a detailed processing process when a content transmission request is made from a host side terminal.

8 is a flowchart showing a detailed processing process when a content transmission request is made from a host side terminal.

Fig. 9 is a flowchart showing a detailed processing process when a content transmission request is made from a guest terminal.

<Description of the code>

1: web server

2: host terminal

3: guest terminal

4: session server

4a: First Session Server

4b: Second Session Server

10: Key, certificate memory means

11: Means for sending public keys and certificates

12: common key receiving means

13: Common key decryption means

14: encryption means

15: server-side content storage means

16: server-side content transmission means

20: Host side public key certificate reception means

21: Host side public key certificate storage means

22: public key, certificate transmission means

23: Host side key receiving means

24: Host side common key creation means

25: Host side common key storing means

26: Host side common key encryption means

27: Host side common key transmission means

28: Host side content receiving means

29: Host side content decoding means

30: Host side content storing means

31: Host side content digest transmission means

32: Host side content acquisition means

33: Host side update means

40: Guest side public key certificate reception means

41: Guest side public key, certificate storing means

42: Key generation means for guest side hash

43: Key storing means for guest side hash

44: Key encryption means for guest side hash

45: Key transmission means for guest side hash

46: content transmission / reception means on the guest side

47: Guest side digest reception means

48: Guest side digest comparison means

49: Guest side content storing means

50: guest side content acquisition means

51: Guest side update means

<Best Mode for Carrying Out the Invention>

An example of the overall system configuration of the present invention is shown in FIG. 1, the system configuration of the web server 1 is shown in FIG. 2, the system configuration of the host side terminal 2 is shown in FIG. 3, and the system configuration of the guest side terminal 3 is shown in FIG. 4 is shown.

The web server 1 is a server that transmits the content in response to a content transmission request from the host-side terminal 2.

The host side terminal 2 and the guest side terminal 3 are terminals which perform synchronous processing through each session server 4, and the host side terminal 2 transmits a content transmission request to the web server 1. Then, the content is received from the web server 1. The received content is then sent to the guest terminal 3 via the session server 4. The guest terminal 3 receives the content stored and displayed by the host terminal 2 from the host terminal 2 via the session server 4 and displays the content on the guest terminal 3 to synchronize the processing. Is a running terminal.

In addition, in this specification, in order to clarify each function and the processing process of the host side terminal 2 and the guest side terminal 3, each function was demonstrated as separate terminals, However, in order to actually perform a synchronous process, The computer terminal is provided with all the functions of the host terminal device 2 and the guest terminal 3, so that either the host terminal 2 or the guest terminal 3 can be implemented according to the aspect. Is preferable. In this case, the functions duplicated in the host side terminal 2 and the guest side terminal 3 may be integrated into one.

The session server 4 receives a connection request from the host side terminal 2 and the guest side terminal 3, and after each terminal logs in, a session between the host side terminal 2 and the guest side terminal 3. (In this specification, although referred to as session server 4, it may be a normal computer terminal or a computer device (router, hub, etc.) not necessarily a server). In the present specification, the session server 4 establishing a session with the host side terminal 2 is the first session server 4a, and the session server 4 establishing a session with the guest side terminal 3 is the second session server. By setting (4b) and further establishing a session by the first session server 4a and the second session server 4b, a case of establishing a session between the host side terminal 2 and the guest side terminal 3 will be described. Although it demonstrates, the host side terminal 2 and the guest side terminal 3 may establish a session on the same session server 4.

Further, each session of the host side terminal 2 and the first session server 4a, the guest side terminal 3 and the second session server 4b, the first session server 4a and the second session server 4b. The session is established by the communication which can ensure well-known security, such as SSL, respectively. The data transmitted / received in the synchronous processing between the host terminal 2 and the guest terminal 3 may be SSL or the like through the first session server 4a and the second session server 4b without the specification. The security between the host side terminal 2 and the guest side terminal 3 is transmitted and received by secured communication. Therefore, even if it is not specified, for example, data is transmitted from the host terminal 2 to the guest terminal 3 or from the guest terminal 3 to the host terminal 2. In the description, the data is transmitted / received by communication (for example, SSL) in which security between the host terminal 2 and the guest terminal 3 is secured, and is substantially encrypted.

The web server 1 includes a key certificate storage means 10, a public key certificate transmission means 11, a common key receiving means 12, a common key decryption means 13, an encryption means 14, and a server side. It has a content storing means 15 and a server-side content transmitting means 16.

The key certificate storage means 10 is a means for storing the server certificate which proves the validity of the web server 1, the public key and the secret key which the web server 1 uses.

The public key certificate transmission means 11 is a means for transmitting the server certificate and the public key stored in the key certificate storage means 10 to the host side terminal 2.

The common key receiving means 12 includes a host-side common key created by the host-side terminal 2 and encrypted with a public key, a cryptographic method, and a guest created by the guest-side terminal 3 and encrypted with a public key. A means for receiving the side hash key and its hash function from the host side terminal 2. In addition, in this specification, about an encryption method and a hash function, the algorithm itself is not transmitted / received, but the identifier which identifies them is transmitted from the host side terminal 2, and it is received by the common key receiving means 12. .

The common key decrypting means 13 stores the host-side common key encrypted by the public key received by the common key receiving means 12 and the guest-side hash key encrypted by the public key, with key and certificate storage means. Means for decrypting with a secret key corresponding to the public key stored in (10), and using the host-side common key and cipher system of the plain text, the guest-side hash key of the plain text, and a hash function thereof.

The server-side content storage means 15 is a means for storing content displayed by the host-side terminal 2 and the guest-side terminal 3, and the content includes various data such as text data, image data, and audio data. Included. An example of the content is the content of a web site.

The encryption means 14 extracts the content corresponding to the content transmission request which the web server 1 received from the host side terminal 2 from the server side content storage means 15, and shares the digest of the content in common. And means for encrypting the content and the digest of the content based on the host-side common key and the encryption method based on the guest-side hash key decrypted by the key decryption means 13 and its hash function. Digest also refers to fixed-size data generated by applying one direction function, such as a hash function with a key (HMAC-MD5, HMAC-SHA-1, etc.), to any amount of data.

The server-side content transmission means 16 is a means for transmitting the content and the digest encrypted by the host-side common key by the encryption means 14 to the host-side terminal 2.

The host side terminal 2 includes a host side public key / certificate receiving means 20, a host side public key / certificate storing means 21, a public key / certificate transmitting means 22, and a host side key receiving means 23. Host-side common key generating means 24, host-side common key storing means 25, host-side common key encrypting means 26, host-side common key transmitting means 27, host-side content receiving means 28, The host side content decoding means 29, the host side content storing means 30, the host side content digest sending means 31, the host side content obtaining means 32, and the host side updating means 33 are provided.

The host-side public key / certificate receiving means 20 is a server certificate and a public key of the web server 1 transmitted by the public-key / certificate transmitting means 11 of the web server 1 to the host-side terminal 2. Means of receiving.

The host side public key certificate storing means 21 is a means for storing the server certificate and the public key received by the host side public key certificate receiving means 20.

The public key / certificate transmitting means 22 sends the certificate and public key of the web server 1 received by the host-side public key / certificate receiving means 20 to the guest-side terminal 3 by the session server 4. (First session server 4a, second session server 4b).

The host-side key receiving means 23 generates a guest-side hash key and its hash function generated by the guest-side terminal 3 and encrypted by the public key from the guest-side terminal 3 to the session server 4 (the first server). Means for receiving via the first session server 4a and the second session server 4b).

When the host-side common key creation means 24 encrypts the content transmitted from the web server 1 by a well-known common key cryptography method (for example, DES, Triple-DES, RC4, RC2, IDEA, etc.), A means for creating a host-side common key to be used.

The host side common key storage means 25 is a means for storing the host side common key created by the host side common key creating means 24 and its encryption method.

The host-side common key encrypting means 26 receives the host-side common key created by the host-side common key generating means 24 and its encryption method from the web server 1, and receives the host-side public key / certificate storing means 21. Is a means for encrypting with the public key of the web server 1.

The host-side common key transmitting means 27 is an encrypted guest-side hash key received from the guest-side terminal 3 at the host-side key receiving means 23, its hash function, and the host-side common key encryption means 26. Is a means for transmitting to the web server 1 the host-side common key and its encryption method, which are encrypted by the &quot;

When the host-side content acquisition means 32 receives a content display request (for example, input of a URL or selection of a link, etc.) from the user, the host-side content acquisition means 32 acquires the content from the host-side content storage means 30 (described later). And means for performing display of the corresponding content on the host terminal 2 using known display means such as a web browser.

When the host-side content obtaining means 32 receives the content update event (described later) from the host-side updating means 33 (described later), the host-side content obtaining means 32 acquires the corresponding content from the host-side content storing means 30, and the web browser. It is a means for displaying the corresponding content in the host terminal 2 using known display means such as such.

The host-side content receiving means 28 is provided for acquiring the content from the web server 1 when the content requested by the host-side content obtaining means 32 does not exist in the host-side content storing means 30. A means for transmitting a content transmission request to the web server 1 and receiving content and digest encrypted with the host-side common key from the web server 1.

The host side updating means 33 indicates that the new content is stored in the host side content obtaining means 32 and the guest terminal 3 when the host side content storing means 30 stores the new content. A means for notifying the content update event indicated. It is also a means for receiving a content update event from the guest side terminal 3 and notifying the host side content acquiring means 32 of the content update event. In addition to updating the content, the content update event may include information indicating the location of the content such as the URL and the location of the file.

The host-side content decrypting means 29 uses the host-side common key which stores the content and digest which were received by the host-side common key received from the web server 1 in the host-side common key storage means 25. And decrypted by the encryption method and stored in the host-side content storage means 30.

The host side content storage means 30 is a means for storing the content decoded by the host side content decoding means 29.

The host-side content digest transmission means 31 stores the content stored in the host-side content storage means 30 and the digest decoded by the host-side content decoding means 29, the session server 4 (the first session server). (4a) and means for transmitting to the guest terminal 3 via the second session server 4b. When the content transmission request is received from the guest terminal 3, the content is extracted from the host content storage means 30 and transmitted to the guest terminal 3.

The guest side terminal 3 includes a guest side public key / certificate receiving means 40, a guest side public key / certificate storage means 41, a guest side hash key generating means 42, and a guest side hash key storage means. (43), guest-side hash key encryption means 44, guest-side hash key transmission means 45, guest-side content transmission / reception means 46, guest-side digest reception means 47, and guest-side digest comparison means ( 48, guest-side content storage means 49, guest-side content acquisition means 50, and guest-side update means 51. As shown in FIG.

The guest-side public key / certificate receiving means 40 includes a session server 4 (a first session server 4a and a second session server 4b) of a public key / certificate transmitting means 22 of the host-side terminal 2. Means for receiving the server certificate and the public key of the web server 1 transmitted to the guest-side terminal 3 through)).

The guest-side public key / certificate storage means 41 is a means for storing the server certificate and the public key received by the guest-side public key / certificate receiving means 40.

The guest-side hash key generation means 42 is a hash function having a key for creating a digest of the content (in this specification, a hash function having a key is simply called a hash function. For example, HMAC-MD5 and HMAC-SHA). -1, etc.) is a means for creating a guest-side hash key.

The guest-side hash key storing means 43 is a means for storing the guest-side hash key created by the guest-side hash key generating means 42 and its hash function.

The guest-side hash key encrypting means 44 receives the guest-side hash key and its hash function generated by the guest-side hash key generation means 42 from the host-side terminal 2, and receives the guest-side public key certificate. It is a means for encrypting with the public key of the web server 1 stored in the storage means 41.

The guest-side hash key transmitting means 45 stores the guest-side hash key encrypted by the guest-side hash key encrypting means 44 and its hash function using the session server 4 (first session server 4a, Means for transmitting to the host-side terminal 2 via the second session server 4b).

When the guest-side content acquiring means 50 receives a content display request (for example, input of a URL or selection of a link, etc.) from the user, the guest-side content acquiring means 50 acquires the corresponding content from the guest-side content storage means 49 (described later). And means for performing display of the corresponding content on the guest terminal 3 using a known display means such as a web browser.

Further, when the guest-side content acquiring means 50 receives the content update event from the guest-side updating means 51 (described later), the guest-side content acquiring means 50 acquires the corresponding content from the guest-side content storing means 49, such as a web browser or the like. It is a means for displaying the content by using known display means. In the case of displaying the content, the content that could not be authenticated by the guest-side digest comparison means 48 described later may be displayed after not displaying or notifying the user of the possibility of alteration.

The guest-side content transmission / reception means 46, when the content requested by the guest-side content acquisition means 50 does not exist in the guest-side content storage means 49, the host-side terminal 2 in the session. The request for acquiring the content is transmitted, the host terminal 2 receives the content acquired from the web server 1 and stored in the host content storage means 30 from the host terminal 2, and the content is received. Is stored in the guest-side content storage means 49.

The guest-side updating means 51, when the guest-side content storing means 49 stores new content, gives a guest a content update event indicating that the new content is stored in the guest-side content obtaining means 50. It is a means for notifying the side content obtaining means 50. It is also a means for receiving a content update event from the host side terminal 2 and notifying the guest side content acquiring means 50 of the content update event.

The guest-side digest reception means 47 is a means for receiving a digest transmitted by the host-side content digest entry transmitting means 31 of the host-side terminal 2.

The guest-side digest comparison means 48 determines the digest based on the guest-side hash key stored in the guest-side hash key storage means 43 from the content received by the guest-side content transmission / reception means 46 and the hash function thereof. The created digest and the digest received from the guest-side digest receiving means 47 from the host-side terminal 2 are compared, and if matched, received by the guest-side content transmission / reception means 46 and stored in the guest-side content. The content stored in the means 49 is a means for authenticating as legitimate content (unmodified content).

The guest-side content storage means 49 is a means for storing the content received by the guest-side content transmission / reception means 46.

<First Embodiment>

Next, an example of the flow of the process of this invention is demonstrated using the conceptual diagram of FIG. 5, the flowchart of FIG. 6-9, and the system block diagram of FIG.

First, the case where the synchronization request is executed between the host side terminal 2 and the guest side terminal 3 will be described in the case where the display request of the content from the host side terminal 2 is transmitted to the web server 1.

In order to execute the synchronization process, each user of the host side terminal 2 and the guest side terminal 3 logs in to the session server 4 from each terminal, and sets the host side terminal 2 to the host side of the synchronization process. The guest side terminal 3 is set as the guest side of the synchronization process, and a session is established with the session server 4 (S100). That is, the host side terminal 2 establishes a session with the first session server 4a, the guest side terminal 3 establishes a session with the second session server 4b, and the first session server. By further establishing a session between 4a and the second session server 4b, a session is established between the host side terminal 2 and the guest side terminal 3.

Further, when establishing a session of S100, a session is established in a secure data communication environment such as SSL. Specifically, of the host side terminal 2 and the first session server 4a, the guest side terminal 3 and the second session server 4b, the first session server 4a and the second session server 4b. By establishing a session in SSL for data communication between the respective terminals, a secure data communication environment is established between the host side terminal 2 and the guest side terminal 3.

The user of the host-side terminal 2 makes a request for displaying the content of the URL or link by inputting a URL or selecting a link, for example (S110). In response to the content display request, the host-side content obtaining means 32 of the host-side terminal 2 transmits the content corresponding to the URL or link to the host-side content storing means 30 of the host-side terminal 2. It is confirmed whether the memory is stored (S120).

When the content exists in the host-side content storage means 30 (S130), the host-side content acquisition means 32 of the host-side terminal 2 acquires the content from the host-side content storage means 30. Then, the content is displayed on the host terminal 2 by a web browser or the like (S140).

In addition, since the content displayed by the host-side terminal 2 is changed, the host-side update means 33 of the host-side terminal 2 changes the content update event to the session server 4 (first session server 4a). The guest side terminal 3 is notified via the second session server 4b (S150).

The guest-side update means 51 of the guest-side terminal 3 that has received the notification of the content update event from the host-side terminal 2 sends the content update event to the guest-side content acquisition means 50 of the guest-side terminal 3. Notice).

The guest-side content acquiring means 50 of the guest-side terminal 3 confirms whether or not the corresponding content is stored in the guest-side content storage means 49, and when not storing, the guest-side content transmission / reception The means 46 transmits the host-side content digest transmission means 31 of the host-side terminal 2 via the session server 4 (the first session server 4a and the second session server 4b). A content transmission request for the purpose of transmitting the content is transmitted (S160). In addition, when it stores as a result of the said confirmation, the guest side terminal 3 stores the said content memorize | stored in the guest side content storage means 49, without sending a content transmission request to the host side terminal 2. You can display it.

The host-side content digest transmission means 31 of the host-side terminal 2 that has received the content transmission request extracts the corresponding content from the host-side content storage means 30 and sessions with the guest-side terminal 3. The content is transmitted via the server 4 (the first session server 4a and the second session server 4b) (S170).

Guest-side content transmission / reception via the session server 4 (first session server 4a and second session server 4b) from the host-side content digest transmitting means 31 of the host-side terminal 2. Upon reception by the means 46, the content is stored in the guest-side content storage means 49 (S180), and the guest-side content acquisition means 50 of the guest-side terminal 3 is the guest-side content storage means 49. ), The content is acquired, and the content is displayed on the guest terminal 3 using a web browser or the like (S190). By doing this, when the content is stored in the host-side content storage means 30 in S130, the synchronization processing can be executed between the host-side terminal 2 and the guest-side terminal 3.

On the other hand, when the host side content storage means 30 does not store the corresponding content as a result of confirmation of S120 (S130), the corresponding URL or link is transmitted from the host side terminal 2 to the corresponding web server 1. On the other hand, the host-side content receiving means 28 of the host-side terminal 2 transmits a content transmission request (S200).

When the server-side content transmission means 16 of the web server 1 receives the content transmission request from the host-side terminal 2 (S210), the web server 1 and the host-side terminal 2 (and the guest-side terminal ( 3)) The public key / certificate transmitting means 11 of the web server 1 stores the key / certificate storing means 10 in order to secure the security and to authenticate that the content has been transmitted from the legitimate web server 1. ), The server certificate and the public key stored therein are extracted and transmitted to the host terminal 2 (S220).

The server certificate and the public key transmitted from the public key / certificate transmitting means 11 of the web server 1 are received by the host-side public key / certificate receiving means 20 of the host-side terminal 2 and host them. It stores in the side public key certificate storage means 21 (S230). In addition, the server key and the public key received by the host-side public key certificate receiving means 20 are stored in the session key 4 (the first session server 4a, The second session server 4b) transmits the data to the guest terminal 3 (S240).

The guest-side public key certificate receiving means 40 of the guest-side terminal 3 receives the server certificate and the public key transmitted from the host-side terminal 2, and the guest-side public key and certificate storage means 41 is received. The server certificate is stored and the server certificate is authenticated to confirm that the server is a valid server. The guest-side hash key generating means 42 then creates a guest-side hash key for creating a digest of the content transmitted from the web server 1 (S250), and the guest-side hash key and hash function. Is stored in the guest-side hash key storage stage 43.

A web server in which the guest-side hash key encrypting means 44 created by the guest-side hash key creation means 42 and the hash function are stored in the guest-side public key / certificate storage means 41 ( Encrypted by the public key of 1), the guest-side hash key transmission means 45 transmits the host-side terminal (through the session server 4 (the first session server 4a and the second session server 4b)). In step 2), the guest-side hash key encrypted with the public key and its hash function are transmitted (S260).

The host-side key receiving means 23 of the host-side terminal 2 receives the guest-side hash key and hash function encrypted by the public key transmitted from the guest-side terminal 3. In addition, the host-side public key certificate receiving means 20 authenticates the server certificate stored in the host-side public key certificate storing means 21 to confirm that it is a legitimate server. Then, the host-side common key creating means 24 creates a host-side common key for encrypting the content transmitted from the web server 1, and converts the host-side common key and the encryption scheme into the host-side common key storage means ( 25) (S270).

Of the web server 1 in which the host-side common key encryption means 26 stores the host-side common key and the encryption method created by the host-side common key creating means 24 in the host-side public key / certificate storage means 21. The host-side common key encrypted by the public key and encrypted by the host-side common key transmission means 27, its encryption method, and the public key received by the host-side key receiving means 23. The guest-side hash key and its hash function are transmitted to the web server 1 (S280). In addition, S230-S280 may be processed in parallel by the host side terminal 2 and the guest side terminal 3 simultaneously.

The common key receiving means 12 of the web server 1 receives the host-side common key encrypted with the public key, its encryption method, the guest-side hash key encrypted with the public key, and its hash function, The common key decrypting means 13 of the web server 1 decrypts the secret key corresponding to the corresponding public key stored in the key / certificate storage means 10 (S290), and the host-side common key of the plain text and its cipher. Method, the hash key for the guest-side hash of plain text, and its hash function.

The encryption means 14 of the web server 1 which acquired each common key stores the content corresponding to the content transmission request which the web server 1 received from the host side terminal 2 in S210, server side content storage means ( 15), a digest of the content is created using the guest-side hash key decoded by the common key decrypting means 13 and its hash function (S300). Further, the encryption means 14 encrypts the content and the digest of the content again with the host-side common key, and the server-side content transmission means 16 transmits them to the host-side terminal 2 (S310). .

When the host-side content receiving means 28 of the host-side terminal 2 receives the content encrypted by the host-side common key from the web server 1 and the digest thereof, the host-side content decrypting means 29 causes the host-side. Decryption is performed based on the host-side common key stored in the common key storage means 25, and the corresponding content in plain text is stored in the host-side content storage means 30 (S320).

After storing the content in the host-side content storage means 30 in S320, the host-side content acquisition means 32 of the host-side terminal 2 acquires the content from the host-side content storage means 30, and the web. The host terminal 2 displays the corresponding content using a browser or the like (S330).

Since the new content is displayed by this display, the host-side updating means 33 sends the content update event to the guest side via the session server 4 (first session server 4a and second session server 4b). The terminal 3 is notified (S340).

The guest-side update means 51 of the guest-side terminal 3 that has received the notification of the content update event from the host-side terminal 2 notifies the guest-side content acquisition means 50 of the content update event. The guest-side content acquiring means 50 confirms whether or not the corresponding content is stored in the guest-side content storage means 49, but does not store it (the host-side terminal 2 is the web server 1). Since the guest terminal 3 does not store the content), the guest-side content transmission / reception means 46 is connected to the host-side content digest transmission means 31 of the host-side terminal 2. The request for transmission of the corresponding content is transmitted through the session server 4 (the first session server 4a and the second session server 4b) (S350).

A host side terminal that has received a content transmission request from the guest side content transmitting and receiving means 46 of the guest side terminal 3 through the session server 4 (first session server 4a and second session server 4b). The host-side content digest sending means 31 in (2) extracts the content from the host-side content storing means 30 of the host-side terminal 2. The host-side content digest transmitting means 31 transmits the dagest of the corresponding content decoded by the host-side content decoding means 29 and the extracted content to the session server 4 (first session server 4a). ), And transmits to the guest-side terminal 3 via the second session server 4b (S360).

The guest-side digest receiving means 47 of the guest-side terminal 3 receives the digest sent by the host-side content digest transmitting means 31 of the host-side terminal 2, and the guest-side content transmitting and receiving means 46 Receives the content transmitted by the host-side content digest transmitting means 31 of the host-side terminal 2.

The guest-side digest comparison means 48 determines the digest based on the guest-side hash key stored in the guest-side hash key storage means 43 from the content received by the guest-side content transmission / reception means 46 and the hash function thereof. The digest is compared with the digest received by the guest-side digest receiving means 47. If they match, the corresponding content received by the guest-side content transmission / reception means 46 and stored in the guest-side content storage means 49 is authenticated as legitimate content (unmodified content) (S370). When the authentication is made in S370, the guest-side content transmitting and receiving means 46 stores the corresponding content received from the host-side terminal 2 in the guest-side content storing means 49 (S380).

The guest-side content acquiring means 50 acquires the corresponding content from the guest-side content storage means 49 when the content is stored in the guest-side content storage means 49 in this way, and uses the web browser or the like to obtain the content. The corresponding content is displayed on the terminal 3 (S390). In addition, the guest-side content transmission / reception means 46 first stores the content in the guest-side content storage means 49, and the guest-side content acquisition means in the case where the guest-side digest comparison means 48 can authenticate the content. If the content is displayed and the authentication has not been performed, the guest content obtaining means 50 may not display or display the content after notifying the user of the possibility of alteration.

By executing the above process, the guest terminal 3 authenticates the web server 1 as a legitimate server, and then receives the content in a secured state, and receives the host side terminal 2 and the guest side. Synchronous processing can be executed between the terminals 3.

Second Embodiment

Next, in the case where synchronous processing is executed between the host terminal 2 and the guest terminal 3, the display request of the content is sent from the guest terminal 3 to the host terminal 2, and the host side is transmitted. The case where the terminal 2 transmits the content display request to the web server 1 will be described.

In order to execute the synchronization process, each user of the host side terminal 2 and the guest side terminal 3 logs in to the session server 4 from each terminal, and causes the host side terminal 2 to host the synchronization side. The guest side terminal 3 is set as the guest side of the synchronization process, and a session is established with the session server 4 (S500). That is, the host side terminal 2 establishes a session with the first session server 4a, the guest side terminal 3 establishes a session with the second session server 4b, and the first session server. By establishing a session again between (4a) and the second session server 4b, a session is established between the host side terminal 2 and the guest side terminal 3.

Further, when establishing a session of S500, a session is established in a secure data communication environment such as SSL, for example. Specifically, of the host side terminal 2 and the first session server 4a, the guest side terminal 3 and the second session server 4b, the first session server 4a and the second session server 4b. By establishing a session in SSL for data communication between the respective terminals, a secure data communication environment is established between the host side terminal 2 and the guest side terminal 3.

The user of the guest terminal 3, for example, inputs a URL, selects a link, or the like, thereby making a content display request for the URL or link (S510). By the content display request, whether the guest-side content acquiring means 50 of the guest-side terminal 3 stores the content corresponding to the URL or link in the guest-side content storage means 49 of the guest terminal. Confirmation is performed (S520).

When the content exists in the guest-side content storage means 49 (S530), the guest-side content acquisition means 50 of the guest-side terminal 3 acquires the content from the guest-side content storage means 49. The content is displayed on the guest terminal 3 by a web browser or the like (S540).

In addition, since the content displayed by the guest terminal 3 has changed, the guest side updating means 51 of the guest side terminal 3 sends a content update event to the session server 4 (first session server 4a). The host side terminal 2 is notified through the second session server 4b (S550).

The host side update means 33 of the host side terminal 2 which has received the notification of the content update event from the guest side terminal 3 sends the content update event to the host side content acquisition means 32 of the host side terminal 2. Notice).

The host-side content acquisition means 32 of the host-side terminal 2 confirms whether or not the content is stored in the host-side content storage means 30, and stores it in this case. Since the synchronization processing is performed between 2) and the guest terminal 3, the content stored in the guest terminal 3 is also stored in the host terminal 2), and the web server 1 The content stored in the host-side content storage means 30 is displayed on the host-side terminal 2 using a web browser or the like without being transmitted to the host-side content storage means 30 (S560). In this way, when the content is stored in the guest-side content storage means 49 in S530, synchronization processing can be executed between the host-side terminal 2 and the guest-side terminal 3.

On the other hand, as a result of confirmation of S520, when the guest content storage means 49 does not store the corresponding content (S530), the guest content transmission / reception means 46 of the guest terminal 3 connects to the session server ( 4) The content transmission request is transmitted to the host terminal 2 via the first session server 4a and the second session server 4b (S570).

The host-side content receiving means 28 of the host-side terminal 2 that has received the content transmission request from the guest-side terminal 3 sends a content transmission request to the corresponding web server 1 of the URL or link of the content. Transmit (S200).

After that, the processes from S200 to S390 are similarly executed in the same manner as in the first embodiment.

By executing the above-described processing, even when a content transmission request is made from the guest terminal 3, the guest side terminal 3 also authenticates the web server 1 as a legitimate server, similarly to the first embodiment. The content can be received in a secured state, and synchronization processing can be performed between the host side terminal 2 and the guest side terminal 3.

Each means in this invention is only logically distinguishing the function, and may comprise the same area physically or actually.

Further, in the practice of the present invention, it is natural that the storage medium containing a program of software for realizing the functions of the present embodiment is supplied to the system, and the computer of the system is realized by reading and executing the program stored in the storage medium. Do.

In this case, the program itself read from the storage medium realizes the functions of the above embodiments, and the storage medium storing the program naturally constitutes the present invention.

As a storage medium for supplying a program, for example, a magnetic disk, a hard disk, an optical disk, a magneto-optical disk, a magnetic tape, a nonvolatile memory card, or the like can be used.

In addition, by executing the program read by the computer, not only the functions of the above-described embodiments are realized, but also based on the instruction of the program, an operating system or the like running on the computer performs part or all of the actual processing, It goes without saying that the process includes the case where the functions of the above-described embodiments are realized.

Furthermore, after the program read from the storage medium is written into the nonvolatile or volatile storage means included in the function expansion board inserted into the computer or the function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program. It goes without saying that a calculation processing device or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the processing of the above-described embodiment is realized by the processing.

 According to the present invention described above, even when synchronous processing is performed between a plurality of computer terminals, it is possible to execute data communication with security after authenticating that the web server is a legitimate server.

Claims (7)

A data communication method when performing synchronization processing of content stored in a web server between a host side terminal and at least one guest side terminal capable of cryptographic communication via at least one session server, The host terminal, Receiving and storing a server certificate and a public key from the web server, and transmitting the server certificate and the public key to the guest terminal through the session server, The guest terminal, The server certificate and the public key are received from the host terminal, the server certificate is authenticated, a guest side hash key for creating a digest of the content is generated, and the guest side hash key and hash function are generated. Encrypt with the public key, and transmit the encrypted ones to the host-side terminal, The host terminal, Authenticate the received server certificate, create a host-side common key for encrypting the content by a common key cryptography method, encrypt the host-side common key and the common key cryptography with the public key, and encrypt Send the encrypted guest-side hash key and the hash function received from the guest-side terminal to the web server, The web server, Decrypts the encrypted host-side common key and the common key cryptographic scheme, the encrypted guest-side hash key and the hash function received from the host-side terminal based on the secret key corresponding to the public key; Generate the digest by the hash function based on the decrypted guest-side hash key, and encrypt the created digest and the content by the common key cryptography based on the decrypted host-side common key. Send those encrypted to the host-side terminal, The host terminal, Receive the encrypted digest and the content from the web server, decrypt the encrypted digest and content with the created host-side common key, and decrypt the decrypted digest and content to the guest-side terminal through the session server. In addition to the transmission, the content is displayed on the host terminal, The guest terminal, When the decoded digest and the content are received from the host side terminal, a digest is generated from the received content based on the created guest-side hash key and hash function, and the digest and the received digest are compared and matched. And displaying the content in the guest terminal. The method of claim 1, The encrypted communication between the host terminal and the guest terminal is performed by performing encrypted communication between the host terminal and the session server, and between the guest terminal and the session server, respectively. The method according to claim 1 or 2, The synchronous process is, The user of the host terminal selects the display request of the content to confirm whether the host terminal stores the content; When storing, the content corresponding to the content transmission request received from the guest terminal by displaying the content on the host terminal and notifying the guest terminal of a content update event through the session server. Is transmitted to the guest terminal, and the content is displayed at the guest terminal which received it, If it is not stored, the web server is started by transmitting the server certificate and the public key to the host terminal by transmitting the content transmission request from the host terminal to the web server. Data communication method. The method according to any one of claims 1 to 3, The synchronous process is, The user of the guest terminal selects the display request of the content, confirms whether the guest terminal has stored the content, When storing, the host terminal displays the content on the guest terminal and notifies the host terminal terminal of a content update event through the session server, thereby storing the content stored in the host terminal. If it is displayed on the screen, and if it is not stored, it transmits the content transmission request from the guest terminal to the host terminal, and the host terminal that received it stores the content in the host terminal. Check the When the host terminal stores the content, the host terminal displays the content and notifies the guest terminal terminal of a content update event through the session server. The content transmission request is received from the guest terminal. Transmits the content corresponding to to the guest-side terminal, displays the content on the guest-side terminal which has received it, If the host terminal does not store the data, the web server transmits the content transmission request from the host terminal to the web server, and the web server transmits the server certificate and the public key to the host terminal. And a data communication method. A data communication system when performing synchronization processing of content stored in a web server between a host side terminal and at least one guest side terminal capable of cryptographic communication via at least one session server, The web server, Public key certificate transmission means for transmitting the server certificate and public key stored in the key certificate storage means to the host terminal; A host-side common key created by the host-side terminal and encrypted by the public key and its encryption method, and a guest-side hash key and the hash function generated by the guest-side terminal and encrypted by the public key; Common key receiving means for receiving from the host terminal; Common key decryption means for decrypting the encrypted host-side common key, its encryption method, the encrypted guest-side hash key and its hash function by a secret key stored in the public key / certificate storage means; The web server extracts the content corresponding to the content transmission request received from the host-side terminal from the server-side content storage means for storing the content, and extracts the digest of the content from the guest-side hash key and its contents. Encryption means for creating based on a hash function and encrypting the created digest and the content based on the decrypted host-side common key and its encryption method; Server-side content transmission means for receiving the request for transmission of the content from the host-side terminal, transmitting the digest encrypted by the encryption means and the content to the host-side terminal, The host terminal, Host-side public key / certificate receiving means for receiving the server certificate and the public key from the web server and storing them in a host-side public key / certificate storage means; Public key and certificate transmitting means for transmitting the received server certificate and the public key to the guest terminal; Host-side key receiving means for receiving a guest-side hash key and its hash function generated by the guest-side terminal and encrypted by the public key; Host-side common key creating means for creating a host-side common key for use in encrypting the content by a common key cryptography method, and storing the host-side common key and its cryptography method in a host-side common key storage means; Host-side common key encryption means for encrypting the created host-side common key and its encryption method by the public key stored in the host-side public key / certificate storage means; Host-side common key transmitting means for transmitting the encrypted host-side common key and its encryption method, the encrypted guest-side hash key received by the host-side key receiving means, and its hash function to the web server; Host-side content receiving means for transmitting the content transmission request to the web server and receiving a digest and content encrypted by the host-side common key sent from the web server; Host-side content decrypting means for decrypting the received encrypted digest and content with the host-side common key stored in the host-side common key storage means, and storing decrypted content in host-side content storage means; Host-side content digest sending means for transmitting the decoded digest and content to the guest-side terminal via the session server; And host-side content acquiring means for acquiring and displaying the content stored in the host-side content storage means. The guest terminal, Guest-side public key / certificate receiving means for receiving the server certificate and the public key from the host-side terminal and storing them in a guest-side public key / certificate storage means; Guest-side hash key generation means for creating a guest-side hash key for creating a digest of the content by a hash function, and storing the guest hash key and the hash function in the guest-side hash key storage means; , Guest-side hash key encryption means for encrypting the created guest-side hash key and its hash function with the public key stored in the guest-side public key / certificate storage means; Guest-side hash key transmitting means for transmitting the encrypted guest-side hash key and its hash function to the host-side terminal through the session server; Guest-side digest receiving means for receiving the decoded digest from the host-side terminal; Guest-side content transmission / reception means for receiving the decoded content from the host-side terminal and storing it in a guest-side content storage means; From the received content, a digest is created based on the guest-side hash key stored in the guest-side hash key storage means and the hash function, and the created digest is compared with the digest received by the guest-side digest means. If it matches, the guest-side digest comparison means for authenticating the content as legitimate Guest-side content acquisition means for acquiring and displaying the content stored in said guest-side content storage means when authenticating as said legitimate content. Data communication system, characterized in that consisting of. A data communication system used in the web server when performing synchronization processing of content stored in a web server between a host terminal terminal capable of encrypted communication through at least one or more session servers and at least one guest terminal terminal. The data communication system used in the web server, Public key certificate transmission means for transmitting the server certificate and public key stored in the key certificate storage means to the host terminal; A host-side common key created by the host-side terminal and encrypted by the public key and its encryption method, and a guest-side hash key and the hash function generated by the guest-side terminal and encrypted by the public key; Common key receiving means for receiving from the host terminal; Common key decryption means for decrypting the encrypted host-side common key, its encryption method, the encrypted guest-side hash key and its hash function by a secret key stored in the public key / certificate storage means; The web server extracts the content corresponding to the content transmission request received from the host-side terminal from the server-side content storage means for storing the content, and extracts the digest of the content from the guest-side hash key and its contents. Encryption means for creating based on a hash function and encrypting the created digest and the content based on the decrypted host-side common key and its encryption method; Server-side content transmission means for receiving the request for transmission of the content from the host-side terminal, transmitting the digest encrypted by the encryption means and the content to the host-side terminal, In the host terminal, Decrypting the encrypted digest and the content received from the web server with the host-side common key generated by the host-side terminal, and transmitting the decrypted digest and the content to the guest-side terminal through the session server; Display the content on the host-side terminal; In the guest terminal, When the decoded digest and the content are received from the host side terminal, a digest is generated from the received content based on the created guest-side hash key and hash function, and the digest and the received digest are compared and matched. And displaying the content in the guest terminal. A data communication system used by a host terminal when performing synchronization processing of content stored in a web server between a host terminal terminal capable of cryptographic communication via at least one session server and at least one guest terminal terminal, The data communication system used in the host terminal, Host-side public key / certificate receiving means for receiving a server certificate and the public key from the web server and storing them in a host-side public key / certificate storage means; Public key and certificate transmitting means for transmitting the received server certificate and the public key to the guest terminal; Host-side key receiving means for receiving a guest-side hash key and its hash function generated by the guest-side terminal and encrypted by the public key; Host-side common key creating means for creating a host-side common key for use in encrypting the content by a common key cryptography method, and storing the host-side common key and its cryptography method in a host-side common key storage means; Host-side common key encryption means for encrypting the created host-side common key and its encryption method with the public key stored in the host-side public key certificate storage means; Host-side common key transmitting means for transmitting the encrypted host-side common key and its encryption method, the encrypted guest-side hash key received by the host-side key receiving means, and its hash function to the web server; The web server transmits a content transmission request to the web server, and in the web server, the digest generated by using the guest-side hash key and the hash function encrypted by the host-side common key and the content thereof, the web server. Host-side content receiving means for receiving from Host-side content decrypting means for decrypting the received encrypted digest and content with the host-side common key stored in the host-side common key storage means, and storing decrypted content in host-side content storage means; Host-side content digest sending means for transmitting the decoded digest and content to the guest-side terminal via the session server; And host-side content acquiring means for acquiring and displaying the content stored in the host-side content storage means. In the guest terminal, Receive the decoded digest and the content from the host side terminal, create the digest from the received content based on the created guest-side hash key and the hash function, and compare the digest and the received digest. And the content is displayed on the guest terminal when the content is matched.

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