JP2008028868A - Communication proxy system and communication proxy device - Google Patents

Abstract

Transmission efficiency is improved while ensuring security in data communication.
In a communication proxy system, a client proxy device represents a transmission process of a client terminal, and a server proxy device represents a reception process of a server device. The client proxy device 100 issues a unique public key P to the client terminal 300 instead of the public key S of the server device 400, acquires the common key C encrypted by the public key P from the client terminal 300, and obtains the secret key The common key C is shared with the client terminal 300 by decrypting with P. Next, the confidential data encrypted with the shared key C is acquired from the client terminal 300, decrypted once, then compressed, further encrypted, and transmitted to the server device 400. The server proxy device 200 receives the encrypted data from the client proxy device 100, decrypts it, expands it, and transfers it to the server device 400.
[Selection] Figure 4

Description

  The present invention relates to a data communication technique, and more particularly to a technique for improving the transmission efficiency and security of data communication.

  In recent years, with the spread of computers and the development of network technology, the exchange of electronic information via the network has become popular. As a result, many of the business processes that have been conventionally performed on a paper basis are being replaced by network-based processes. Under such circumstances, techniques for preventing theft and falsification of data on a communication path and spoofing of a sender / receiver are becoming more important.

Electronic information is exchanged not only on a wired communication line such as FTTH (Fiber To The Home) but also on a wireless communication line such as a wireless LAN (Local Area Network). With the enhancement of mobile communication terminals such as mobile phones and car navigation systems, an environment in which communication can be easily performed anytime and anywhere is being prepared. Security measures are particularly important for wireless communication lines.
JP 2006-100833 A

  Also, in a wireless communication line, the distance between a mobile communication terminal and a connected base station, the number of mobile communication terminals connected to the base station, and when the mobile communication terminal switches the connected base station. Due to the influence of hand-over, packet loss, and hence packet retransmission processing is likely to occur. Measures to suppress packet loss and improve data transmission efficiency are also required.

  The inventor of the present invention has focused on the fact that the number of occurrences of packet loss itself can be suppressed by compressing the size of data to be transmitted. Data size compression reduces the overall communication network traffic. In the case of a packet-based system, there is an advantage in terms of charge. However, in the case of a general compression technique, a high compression rate can be realized if the type of data has the same pattern repeatedly, but such a repeated pattern is difficult to appear in encrypted data, and the compression rate is low. It will go down.

  The present invention has been completed based on the above-mentioned problem recognition of the present inventor, and its main object is to provide a technique for realizing suitable data communication by ensuring both security and data size compression. There is to do.

An aspect of the present invention is a communication added to a system that transmits encrypted data from a first data processing device to a second data processing device based on a public key issued by a second data processing device. It is a proxy system. This system includes a first communication proxy device proxying transmission processing of the first data processing device and a second communication proxy device proxying reception processing of the second data processing device.
The first communication proxy device issues a unique public key to the first data processing device instead of the public key of the second data processing device, and is encrypted by the public key from the first data processing device. A common key is shared with the first data processing device by acquiring the key and decrypting it with the secret key. Next, the data encrypted with the shared key is acquired from the first data processing apparatus, and once decrypted, compressed, further encrypted, and transmitted to the second data processing apparatus.
The second communication proxy device receives the encrypted data from the first communication proxy device, decrypts it, expands it, and transfers it to the second data processing device on the receiving side.

  By adding such a communication proxy system to an existing encryption communication system, two purposes of efficient data compression and encryption can be achieved.

  It should be noted that any combination of the above-described components, and a representation of the present invention by a method, apparatus, recording medium, and computer program are also effective as an aspect of the present invention.

  According to the present invention, there is an effect in realizing efficient data compression while ensuring communication security.

  In the present embodiment, a client / server system that transmits data from the client terminal 300 to the server apparatus 400 based on SSL (Secure Socket Layer) will be described. SSL is a communication protocol based on a public key cryptosystem.

  The public key cryptosystem is characterized in that an encryption key and a decryption key are different. Public key cryptosystems include various practical schemes such as RSA (Rivest Shamir Adleman) cryptography, Rabin cryptography, and Elgamal cryptography. In any of these, encryption processing and decryption processing are realized by a pair of keys, a public key and a secret key. In a public key cryptosystem, data encrypted with a public key can only be decrypted with a private key. Also, data encrypted with the private key can only be decrypted with the public key. That is, data encrypted with the public key cannot be decrypted with the same public key, and data encrypted with the private key cannot be decrypted with the private key. SSL using the asymmetry of the public key cryptosystem is used in various scenes such as electronic commerce.

FIG. 1 is a sequence diagram for explaining a general SSL mechanism.
In the figure, it is assumed that data to be concealed (hereinafter simply referred to as “confidential data”) is transmitted from the client terminal 300 to the server device 400. First, the client terminal 300 transmits a connection request command to the server device 400 (S10). The connection request command may be a command defined in the communication protocol that the client terminal 300 should transmit before transmitting the confidential data. For example, the connection request command may be a SYN packet (Synchronize Packet) transmitted at the start of a session.

  When receiving the connection request command, the server apparatus 400 generates a public key and a private key (S12). Hereinafter, the public key generated by the server apparatus 400 is referred to as “public key S”, and the secret key is referred to as “secret key S”. The server device 400 transmits a public key certificate including data of the public key S to the client terminal 300 (S14). The public key certificate is X. It is generated in a format based on the 509 standard. In addition to the public key, the public key certificate includes the certificate authority that authenticated the public key, the validity period of the public key, the ID of the server device 400 that is the issuer, and the like.

  Upon receiving the public key certificate, the client terminal 300 generates a common key (S16). Hereinafter, the common key generated by the client terminal 300 is also referred to as “common key C”. However, the client terminal 300 generates a common key C on the condition that a certificate authority for the public key S is registered with reference to a root certificate in which an acceptable certificate authority is registered in advance. To do. The client terminal 300 encrypts the common key C with the public key S (S18). The encrypted common key C is transmitted to the server device 400 (S20). Hereinafter, in order to show that it is encrypted, the description will be made using the symbol “<>”. For example, the encrypted common key C transmitted in S20 is represented as <common key C>. The server apparatus 400 acquires this <common key C>.

  The server apparatus 400 decrypts the <common key C> with the secret key S and takes out the common key C (S22). In this way, the client terminal 300 and the server apparatus 400 share the common key C secretly. Next, the client terminal 300 encrypts the confidential data to be transmitted with the common key C (S24). The client terminal 300 transmits this encrypted <secret data> to the server device 400 (S26). The server apparatus 400 decrypts <confidential data> with the common key C and extracts the confidential data (S28). In this way, confidential data is secretly transmitted from the client terminal 300 to the server device 400. The above is the outline of general SSL communication.

  Even when data is transmitted from the server apparatus 400 to the client terminal 300, the processing contents from S10 to S22 are the same. The server apparatus 400 encrypts the confidential data with the common key C and transmits it to the client terminal 300. In general SSL communication, a common key C is secretly shared by a public key cryptosystem, and secret data is encrypted and decrypted by the common key C. Normally, the public key cryptosystem has a larger processing load than the common key cryptosystem, and therefore the public key S is used only for safely delivering the common key C. Depending on the processing capabilities of the client terminal 300 and the server device 400, the secret data may be encrypted with the public key S instead of the common key C. Hereinafter, in the present embodiment, it is assumed that the secret data is encrypted not by the public key S but by the common key C.

  By the way, the larger the size of the secret data, the longer the time required for transmission and the greater the number of packet transmissions in S26. When the number of packet transmissions increases, packet loss is likely to occur during transmission of confidential data. This is particularly likely in the case of wireless communication. Further, in the case of packet metering, the larger the size of the confidential data, the more expensive the user is costly. In this embodiment, an approach is adopted in which the size of the confidential data is compressed to reduce the number of packet transmissions, thereby improving the transmission time and transmission cost. In order to compress the size of the confidential data, the client proxy device 100 and the server proxy device 200 are added between the client terminal 300 and the server device 400.

FIG. 2 is a hardware configuration diagram of the communication proxy system 310 in the present embodiment.
The client terminal 300 accesses the server devices 400a to 400c via the communication network 350. The client terminal 300 is a mobile communication terminal such as a notebook PC, a mobile phone, a PHS (Personal Handyphone System), or a car navigation terminal, but may be any device that has at least a secret data transmission function compatible with SSL. The server apparatus 400 is an apparatus that receives various connection requests from the client terminal 300 and provides various services. The server apparatus 400 may also be an apparatus having a secret data receiving function corresponding to SSL. The communication network 350 is a communication network including a wireless communication network. The client terminal 300 is connected to the nearest base station and communicates with the server device 400 via the communication network 350.

  In this embodiment, a client proxy device 100 and a server proxy device 200 are added as a communication proxy system 310 to such an SSL-compatible communication system. The client proxy device 100 is a device that proxy the confidential data transmission processing of the client terminal 300 and serves as an interface between the client terminal 300 and the communication network 350. Therefore, the client terminal 300 is connected to the communication network 350 via the client proxy device 100. The client proxy device 100 may be a software module installed in the client terminal 300. The function of the client proxy device 100 may be realized as a part of the function of the base station, or may be a device separate from the client terminal 300 and the base station in hardware. In this embodiment, the client proxy device 100 will be described as a single device connected to the communication network 350 in place of the client terminal 300.

  The server proxy device 200 is a device that proxy the confidential data reception process of the server device 400 and serves as an interface between the server device 400 and the communication network 350. Accordingly, each server device 400 is connected to the communication network 350 via the server proxy device 200. Server proxy device 200 may be a software module installed in server device 400. The function of the server proxy device 200 may be realized as a part of a proxy server or firewall function that collects a plurality of server devices 400. The communication line connecting the server proxy device 200 and the server device 400 may be a line with limited communication nodes such as an intranet, a wide area line such as the Internet, or a combination thereof. In this embodiment, the server proxy device 200 will be described as a single device connected to the communication network 350 in place of the server device 400.

  Note that the relationship between the client and the server does not have to be a fixed relationship. It goes without saying that the communication proxy system 310 can be applied even in a communication system in which the transmission side and the reception side are appropriately switched between nodes. Of course, the present invention can also be applied to a system that directly communicates between nodes such as P2P (Peer to Peer).

The following three patterns are assumed for transmission of confidential data.
A. A pattern in which secret data is transmitted from the client terminal 300 to the server device 400 in a system in which the relationship between the client and the server is fixed. This is so-called upstream transmission.
B. A pattern in which confidential data is transmitted from the server apparatus 400 to the client terminal 300 in a system in which the relationship between the client and the server is fixed. This is so-called downstream transmission.
C. A pattern in which secret data is transmitted from a transmitting node to a receiving node in a system in which a data transmitting entity and a data receiving entity are appropriately switched between nodes as in P2P.

In the present specification, the description will be made on the assumption that the pattern A is used, and the pattern B is also added.
The pattern C is the same as the pattern A. The transmission processing of the transmission node is represented by the transmission function of the client proxy device 100 described in detail below. The reception process of the reception node is proxyed by the reception function of the server proxy device 200 described in detail below. In the case of a communication system that transmits secret data bidirectionally as in the above pattern C, if a communication proxy device having functions of both the client proxy device 100 and the server proxy device 200 is installed for each node, Good. When it becomes a transmission node, this communication proxy device proxyes the transmission process. When it becomes a reception node, the communication proxy device performs reception processing as a proxy.

FIG. 3 is a sequence diagram when the data compression processing by the communication proxy system 310 is added to the SSL communication processing of FIG. Here, the pattern A is assumed.
This figure shows a sequence in the case where data compression / decompression processing is simply added to the SSL communication processing of FIG. The actual communication process in the present embodiment will be described with reference to FIG. 4 and subsequent figures. In order to clarify the features, first, the basic process flow and its problems will be described with reference to FIG. Will be described.

  When the client terminal 300 transmits a connection request command to the server device 400, the client proxy device 100 relays the connection request command and transfers it to the server device 400 (S10). The server proxy device 200 also receives the connection request command instead of the server device 400 and then transfers the connection request command to the server device 400. In the transmission of the public key certificate (S14) and the transmission of <common key C> (S20), the client proxy device 100 and the server proxy device 200 relay data, but the basic processing from S10 to S22 is performed. The flow of is the same as that described in relation to FIG. Therefore, the secret data encryption process in S24 will be described.

The client terminal 300 encrypts the secret data with the common key C (S24), and transmits <secret data> to the server device 400 (S26). The client proxy device 100 receives <confidential data> and compresses it using a predetermined data compression method (S29). As a compression method, a known compression technique such as JPEG (Joint Photographic Experts Group) or ZIP may be applied according to the type of confidential data. The client proxy device 100 transmits the compressed <secret data> to the server device 400 (S30). Hereinafter, the symbol “[]” will be used to indicate that compression is performed. For example, <confidential data> compressed in S29 is represented as [<confidential data>]. To summarize the process so far,
Confidential data → Encryption (S24) → <Confidential data> → Compression (S29) → [<Confidential data>]
It becomes. [<Confidential data>] is received by the server proxy device 200 and extracted by the server proxy device 200 (S32). The server proxy device 200 transfers the <secret data> after deployment to the server device 400 (S34). The server device 400 decrypts the <secret data> with the common key C as shown in FIG. 1 (S28). Summary,
[<Confidential data>] → development (S32) → <confidential data> → decryption (S28) → confidential data.

  According to such a processing method, the size of [<confidential data>] transmitted in S30 can be made smaller than the <confidential data> transmitted in S26 of FIG. Communication security can also be secured. In general, the more the repeated patterns appear in the secret data, the higher the compression rate. However, when the secret data is encrypted, the frequency of appearance of this repeated pattern is reduced and the compression rate is lowered. Therefore, in order to further improve the transmission efficiency, a device for increasing the compression rate in S29 is required.

FIG. 4 is a sequence diagram showing a data compression process in the present embodiment.
The processing that is the premise of the processing shown in FIG. 4 is the same as the processing content from S10 to S22 of FIG. In FIG. 4, the process of encrypting confidential data in S24 will be described. First, the client terminal 300 encrypts the confidential data with the common key C (S24). The client terminal 300 transmits <secret data> to the server apparatus 400 (S26). The client proxy device 100 acquires this <secret data> and decrypts it with the common key C (S36). For this reason, the client proxy device 100 needs to receive the common key C from the client terminal 300 in advance. When the client proxy device 100 is realized as a software module installed in the client terminal 300, the client proxy device 100 encrypts the common key C with the public key S when the client terminal 300 generates the common key C in S16. You can receive it before Alternatively, the client proxy device 100 and the client terminal 300 may implicitly share a common key C that is statically generated in advance. A method of sharing the common key C between the client terminal 300 and the client proxy device 100 in the present embodiment will be described in detail later with reference to FIG.

  The client proxy device 100 compresses the decrypted confidential data (S38). Since the compression is performed after decoding, it is easy to realize a higher compression rate than the compression of S29 in FIG. The client proxy device 100 encrypts the compressed [secret data] with a predetermined common key (S40). This common key is hereinafter referred to as “common key P”. The common key P may be implicitly shared between the client proxy device 100 and the server proxy device 200 in advance, or may be shared between the client proxy device 100 and the server proxy device 200 by an SSL mechanism. Good. The client proxy device 100 transmits <[secret data]> encrypted with the common key P after compression to the server device 400 (S42).

To summarize the processing on the sender side:
Confidential data → Encryption (S24) → <Confidential data> → Decryption (S36) → Confidential data → Compression (S38) → [Confidential data] → Encryption (S40) → <[Confidential data]>
It becomes.

  Upon receiving <[secret data]>, the server proxy device 200 decrypts it with the common key P (S44) and expands it (S46). The server proxy device 200 encrypts the expanded secret data with a predetermined common key (S48). This common key is hereinafter referred to as “common key Q”. The server proxy device 200 transfers the <secret data> encrypted with the common key Q to the server device 400 (S50). The server apparatus 400 acquires the secret data by decrypting the <secret data> with the common key Q (S52). The server device 400 needs to receive the common key Q from the server proxy device 200 in advance. When the server proxy device 200 is realized as a software module installed in the server device 400, the server device 400 may receive it as it is when the server proxy device 200 generates the common key Q. Alternatively, the server proxy device 200 and the server device 400 may implicitly share the common key Q in advance. A method of sharing the common key Q between the server proxy device 200 and the server device 400 in the present embodiment will be described in detail later with reference to FIG.

To summarize the processing on the receiving side:
<[Secret data]> → decryption (S44) → [secret data] → development (S46) → secret data → encryption (S48) → <secret data> → decryption (S52) → secret data.

  Note that the common key C generated by the client terminal 300 and the common key P used for encryption of the secret data may be the same. For example, the client proxy device 100 shares the common key C among the client terminal 300, the client proxy device 100, and the server proxy device 200 by secretly passing the common key C to the server proxy device 200 by an SSL mechanism. May be. Similarly, the common key Q and the common key P used between the server proxy device 200 and the server device 400 may be the same. That is, the common keys C, P, and Q are not necessarily separate.

Further, after S48, when communication security from the server proxy device 200 to the server device 400 can be ensured, the server proxy device 200 may transfer the confidential data to the server device 400 without encryption.
The basic principle of the communication processing process in this embodiment is as shown in FIG. Hereinafter, after describing the specific configurations of the client proxy device 100 and the server proxy device 200, focusing on the common key C and Q sharing method and the authentication of a public key certificate (described later) issued by the server device 400, in particular. The processing contents of the communication proxy system 310 will be described in more detail.

FIG. 5 is a functional block diagram of the client proxy device 100.
Each block shown here can be realized in hardware by an element such as a CPU of a computer or a mechanical device, and in software it is realized by a computer program or the like. Draw functional blocks. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms by a combination of hardware and software. The same applies to the server proxy device 200 shown in FIG.
Here, functions to be exhibited by each block will be mainly described, and specific actions thereof will be described with reference to FIG.

  The client proxy device 100 includes a user interface processing unit 110, a proxy interface processing unit 120, a network interface processing unit 130, a data processing unit 140, and a key data holding unit 180.

  The user interface processing unit 110 is in charge of processing related to the entire user interface such as input processing from the user and information display for the user. The proxy interface processing unit 120 is in charge of processing related to the entire interface with the client terminal 300. The network interface processing unit 130 is in charge of communication with the server proxy device 200 and the server device 400 via the communication network 350. The data processing unit 140 executes various data processing based on data acquired from the user interface processing unit 110, the proxy interface processing unit 120, and the network interface processing unit 130. The data processing unit 140 also serves as an interface among the user interface processing unit 110, the proxy interface processing unit 120, the network interface processing unit 130, and the key data holding unit 180. The key data holding unit 180 stores data of various keys such as a common key, a public key, and a secret key.

The proxy interface processing unit 120 includes a transmission data acquisition unit 122, a common key acquisition unit 124, and a public key issue unit 126.
The transmission data acquisition unit 122 acquires <secret data> to be transmitted from the client terminal 300 in S26 of FIG. As already described, this <secret data> is encrypted with the common key C. The public key issuing unit 126 issues a unique public key to the client terminal 300. The public key that the client proxy device 100 uniquely issues to the client terminal 300 (hereinafter referred to as “public key P”) will be described in detail later. The secret key generated in pair with the public key P is referred to as “secret key P”. The common key acquisition unit 124 acquires <common key C> encrypted with the public key P from the client terminal 300.

  The network interface processing unit 130 includes a data transmission unit 132. The data transmission unit 132 transmits <[secret data]> to the server device 400 as described in relation to S <b> 42 of FIG. 4.

The data processing unit 140 includes a compression processing unit 150 and a key processing unit 160.
The compression processing unit 150 performs processing for compressing confidential data. The compression processing unit 150 includes a transmission data decryption unit 152, a transmission data compression unit 154, and a transmission data encryption unit 156. The transmission data decryption unit 152 decrypts <secret data> with the common key C in S36 of FIG. The transmission data compression unit 154 compresses the confidential data after decryption in S38 of FIG. The transmission data encryption unit 156 encrypts the [secret data] after compression in S40 of FIG.

The key processing unit 160 performs processing related to generation / acquisition of a common key, public key, and secret key. The key processing unit 160 includes a public key generation unit 162, a common key decryption unit 164, a connection request detection unit 166, a certificate authority registration unit 168, and a public key authentication unit 170.
The public key generation unit 162 generates a public key P unique to the client proxy device 100. At this time, a secret key P corresponding to the public key P is also generated. The common key decryption unit 164 decrypts the <common key C> received from the client terminal 300 with the secret key P. The connection request detection unit 166 detects transmission of a connection request command by the client terminal 300. The certificate authority registration unit 168 registers the certificate authority of the public key P in the root certificate of the client terminal 300. Specific processing contents will be described in detail with reference to FIG. The public key authenticating unit 170 authenticates the public key S of the server device 400. Specific processing contents will be described in detail with reference to FIG.

FIG. 6 is a functional block diagram of the server proxy device 200.
The server proxy device 200 includes a user interface processing unit 210, a proxy interface processing unit 220, a network interface processing unit 230, a data processing unit 240, and a key data holding unit 280.

  The user interface processing unit 210 is in charge of processing related to the entire user interface such as input processing from the user and information display to the user. The proxy interface processing unit 220 is in charge of processing related to the entire interface with the server device 400. The network interface processing unit 230 communicates with the client proxy device 100 and the client terminal 300 via the communication network 350. The data processing unit 240 executes various data processing based on data acquired from the user interface processing unit 210, the proxy interface processing unit 220, and the network interface processing unit 230. The data processing unit 240 also serves as an interface among the user interface processing unit 210, the proxy interface processing unit 220, the network interface processing unit 230, and the key data holding unit 280. The key data holding unit 280 stores data of various keys such as a common key, a public key, and a secret key.

The proxy interface processing unit 220 includes a data transfer unit 222, a public key acquisition unit 224, and a common key issue unit 226.
The data transfer unit 222 transfers the <secret data> encrypted with the common key Q in S50 of FIG. The public key acquisition unit 224 acquires the public key S by acquiring a public key certificate issued by the server device 400. The acquisition of the public key S will be described in detail with reference to FIG. The common key issuing unit 226 issues a unique common key Q to the server device 400. The issuance of the common key Q will also be described in detail with reference to FIG.
The network interface processing unit 230 includes a data receiving unit 232. The data receiving unit 232 receives <[secret data]> encrypted with the common key P from the data transmitting unit 132 of the client proxy device 100 in S42 of FIG.

The data processing unit 240 includes a development processing unit 250 and a key processing unit 260.
The expansion processing unit 250 performs processing for expanding confidential data. The expansion processing unit 250 includes a reception data decryption unit 252, a reception data expansion unit 254, and a reception data encryption unit 256. The received data decryption unit 252 decrypts <[secret data]> with the common key P in S44 of FIG. The reception data expansion unit 254 expands [secret data] in S46 of FIG. The received data encryption unit 256 encrypts the expanded secret data with the common key Q in S48 of FIG. This <secret data> is sent out by the data transfer unit 222.

The key processing unit 260 performs processing related to generation / acquisition of a common key, public key, and secret key. The key processing unit 260 includes a common key generation unit 262, a common key encryption unit 264, and a public key authentication unit 266.
The common key generation unit 262 generates a common key Q. The common key encryption unit 264 encrypts the common key Q with the public key S. The public key authentication unit 266 authenticates the public key S of the server device 400. The specific contents of the authentication process will be described in detail with reference to FIG.

FIG. 7 is a sequence diagram showing a process for key sharing in the present embodiment.
In the present embodiment, unlike ordinary SSL communication, a communication proxy system 310 is interposed for compression / decompression of secret data. In the case of normal SSL communication, when the server apparatus 400 transmits the public key S to the client terminal 300, the client terminal 300 encrypts the common key C with the public key S and transmits it to the server apparatus 400. Then, the secret data is encrypted with the common key C and transmitted to the server device 400.
However, in order to efficiently compress data, the client proxy device 100 needs to once decrypt <secret data> encrypted with the common key C. For this purpose, the client proxy device 100 must acquire the common key C. If the client terminal 300 and the client proxy device 100 are integrally formed, the client proxy device 100 may receive the common key C directly from the client terminal 300. However, in order for the client proxy device 100 to acquire the common key C before encryption, it is necessary to intervene in the processing process of the client terminal 300. On the other hand, when the client proxy device 100 acquires the encrypted <common key C>, it is not necessary to intervene in the processing process of the client terminal 300. However, in order to decrypt <encrypted key C> after encryption, a secret key S possessed only by server device 400 is required.
In this embodiment, the client proxy device 100 deals with such a problem by generating a unique public key P. The figure is a process executed to share a key among the client terminal 300, the client proxy device 100, the server proxy device 200, and the server device 400 as pre-processing for realizing the processing shown in FIG. Indicates.

  When the client terminal 300 transmits a connection request command to the server device 400 (S10), the server device 400 generates a public key S and a secret key S (S12). The connection request command is relayed by the client proxy device 100 and the server proxy device 200. At this time, the connection request detection unit 166 of the client proxy device 100 detects transmission of a connection request command. The public key generation unit 162 of the client proxy device 100 uniquely generates a public key P and a private key P in response to detection of the connection request command (S13).

  The server apparatus 400 transmits the public key certificate of the public key S according to the normal SSL protocol (S14). The public key acquisition unit 224 of the server proxy device 200 intercepts the public key certificate and acquires the public key S. The public key certificate of the server device 400 is not transmitted to the client terminal 300, but instead, the client proxy device 100 transmits the public key certificate of the public key P to the client terminal 300 (S15). The client terminal 300 acquires the public key certificate as scheduled, but this public key certificate is not actually the public key certificate of the server device 400.

  In the SSL protocol, the server apparatus 400 does not need to recognize that the public key certificate issued by itself is not actually acquired by the client terminal 300. Further, the client terminal 300 does not need to recognize that the public key certificate of the client proxy device 100 is actually acquired instead of the server device 400. Accordingly, the processing can be continued without departing from the framework of the SSL protocol for the client terminal 300 and the server device 400.

  Upon obtaining the public key certificate from the client proxy device 100, the client terminal 300 generates a common key C (S16). The client terminal 300 encrypts the common key C with the public key P (S18) and transmits it to the server device 400 (S20). The client proxy device 100 intercepts the <common key C> and does not transmit it to the server device 400. The common key decryption unit 164 of the client proxy device 100 decrypts the <common key C> with the secret key P (S23). In this way, the common key C is secretly shared between the client terminal 300 and the client proxy device 100.

  On the other hand, when the common key generation unit 262 of the server proxy device 200 obtains the public key certificate from the server device 400, the common key Q is generated (S17). The common key encryption unit 264 of the server proxy device 200 encrypts the common key Q with the public key S (S19). Then, the data transfer unit 222 transmits <common key Q> to the server device 400 (S21). The server apparatus 400 decrypts the <common key Q> with the secret key S (S22). Thus, the common key Q is secretly shared between the server proxy device 200 and the server device 400.

  Through the above processing, after the common key C is shared between the client terminal 300 and the client proxy device 100 and the common key Q is shared between the server proxy device 200 and the server device 400, the process proceeds to the processing shown in FIG. To do. Instead of sending the public key certificate of the server device 400 to the client terminal 300, the client proxy device 100 sends its own public key certificate to the client terminal 300. Further, instead of transmitting the <common key C> of the client terminal 300 to the server device 400, the server proxy device 200 transmits the <common key Q> to the server device 400. Therefore, even if the communication proxy system 310 is added, the client terminal 300 and the server device 400 can execute their respective processes without departing from the SSL protocol.

  Also, the common key and the secret data are transmitted in an encrypted state on the communication path from the client terminal 300 to the client proxy device 100 and the communication path from the server proxy device 200 to the server device 400. Therefore, the security of data transmission can be made more robust. Further, unlike the standard SSL process as shown in FIG. 1, the public key certificate and <common key C> data do not actually pass through the communication network 350. There is also an advantage of further improving the transmission efficiency as a whole by omitting a part of the data transfer process via the communication network 350.

  The client proxy device 100 may generate the public key P and the secret key P each time a connection request command is detected, but generates the public key P and the secret key P only when the connection request command is detected for the first time. You may do that. Thereby, the processing load accompanying the process of S13 or S15 can be reduced. Alternatively, once the public key P and the private key P are generated, they are valid for a predetermined valid period, for example, 30 seconds. When the connection request command is detected again after this valid period has elapsed, A public key P and a private key P may be generated. As the validity period is shorter, the communication security between the client terminal 300 and the client proxy device 100 is improved. As the effective period is longer, the processing load accompanying the processing of S13 and S15 is reduced, and the transmission efficiency is improved. If the generation timing of the public key P / private key P is set based on various conditions such as the processing capability and usage status of the client terminal 300 and the client proxy device 100 and the communication environment between the client terminal 300 and the client proxy device 100 Good.

  Similarly to the public key certificate issued by the server apparatus 400, the public key certificate issued by the client proxy apparatus 100 is also an X. 509 format. In addition to the public key P, the public key certificate includes information such as the certificate authority of the public key P and the validity period of the public key P. In order for the series of processes shown in FIG. 7 to function effectively, the client terminal 300 needs to accept the public key P received from the client proxy device 100 as a valid public key. Therefore, the certificate authority registration unit 168 of the client proxy device 100 registers the certificate authority of the public key P issued by itself in the root certificate of the client terminal 300 in advance. For example, when the client proxy device 100 is installed, the certificate authority registration unit 168 registers the certificate authority of the public key P in the root certificate of the client terminal 300. Through such registration processing, the client terminal 300 can accept the public key P issued by the client proxy device 100, and can smoothly continue processing based on the SSL protocol.

  Here, the above-described pattern B, that is, a case where confidential data is transmitted from the server apparatus 400 to the client terminal 300 will be additionally described. Similarly, in the pattern B, when the client terminal 300 transmits a connection request command to the server apparatus 400, the processing from S12 to S22 in FIG. 7 is executed. The common key C sharing method between the client terminal 300 and the client proxy device 100 and the common key Q sharing method between the server proxy device 200 and the client proxy device 100 can be performed even when the confidential data is downstream. does not change. Therefore, the process until the common key shown in FIG. 8 is shared is basically the same between the A pattern and the B pattern.

Here, when the client terminal 300 requests the server device 400 to download confidential data, the processing described with reference to FIG. 4 is started. However, in the pattern B, each process shown in FIG. 4 is modified as follows.
S24: The server apparatus 400 encrypts the confidential data with the common key Q.
S26: The server device 400 transmits <secret data> encrypted by the common key Q to the server proxy device 200.
S36: The server proxy device 200 decrypts <confidential data> with the common key Q.
S38: The server proxy device 200 compresses the decrypted confidential data.
S40: The server proxy device 200 encrypts the compressed [secret data] with the common key P.
S42: The server proxy device 200 transmits <[secret data]> to the client proxy device 100.
S44: The client proxy device 100 decrypts <[secret data]> with the common key P.
S46: The client proxy device 100 expands [secret data].
S48: The client proxy device 100 encrypts the secret data with the common key C.
S50: The client proxy device 100 transmits the encrypted <secret data> to the client terminal 300.
S52: The client terminal 300 decrypts <secret data> with the common key C.
In this way, transmission of confidential data from the server device 400 to the client terminal 300 is realized. In order to enable such downstream transmission, the server proxy device 200 needs to have a transmission function of the client proxy device 100 of FIG. Specifically, the server proxy device 200 further includes a transmission data acquisition unit 122, a compression processing unit 150, and a data transmission unit 132 of the client proxy device 100. The client proxy device 100 also needs to have the reception function of the server proxy device 200 of FIG. Specifically, the client proxy device 100 further includes a data receiving unit 232, a development processing unit 250, and a data transfer unit 222 of the server proxy device 200.

FIG. 8 is a sequence diagram illustrating a processing process in which the server proxy device 200 authenticates the public key certificate issued by the server device 400.
In an organization such as a company, it may be desired to operate a plurality of server devices 400 with the same security policy. For example, it is assumed that the certificate authority for public key certificates issued by each server device 400 in the organization is limited to six types of certificate authorities A to F. When a new server device 400 is added, it is convenient if it is possible to automatically check whether the certificate authority of the public key certificate issued by the server device 400 corresponds to any of the above A to F. FIG. 6 is a sequence diagram when such authentication processing is performed in the server proxy device 200 proxying the reception processing of the plurality of server devices 400.

  When the client terminal 300 transmits a connection request command to the server device 400 (S10) and the server device 400 generates the public key S / secret key S (S12), the server device 400 obtains the public key certificate of the public key S. The data is transmitted to the client terminal 300 (S14). This public key certificate includes the certificate authority name of the public key S. The public key acquisition unit 224 of the server proxy device 200 acquires a public key certificate, the public key authentication unit 266 refers to its own root certificate, and the public key S certificate authorities are A to F. It is determined whether any of them corresponds (S54). The authentication result is notified to the client proxy device 100 (S56).

  If the authentication is successful (Y in S58), the public key generation unit 162 of the client proxy device 100 generates a public key P and a private key P (S13). The public key issuing unit 126 of the client proxy device 100 transmits a public key certificate including the public key P to the client terminal 300 (S15). The subsequent processing is as described with reference to FIG.

  On the other hand, if the authentication fails (N in S58), the user interface processing unit 110 of the client proxy device 100 displays a warning screen indicating the authentication failure (S60). While the warning screen is displayed, the user selects whether or not the public key S is permitted at his / her own risk (S62). If it is permitted (Y in S62), the process proceeds to S13. If not permitted (N in S62), the process ends without the public key certificate being issued from the client proxy device 100. If permitted in S62, the network interface processing unit 130 may notify the server proxy device 200 of the permission. Then, the public key authentication unit 266 of the server proxy device 200 may newly register the certificate authority permitted in S62 in its own root certificate. According to such a processing method, the root certificate of the server proxy device 200 can be changed from the client proxy device 100.

  If the authentication policy of each client terminal 300 is applied in the server proxy device 200, the authentication policy of each client terminal 300 for the public key certificates issued by the plurality of server devices 400 can be managed in an integrated manner. In the authentication process of S54, the validity period of the public key S described in the public key certificate is compared with the current date and time to determine whether the public key S is within the validity period. Also, it is determined whether the ID of the server device 400 described in the public key certificate matches the actual transmission source of the public key certificate. In this way, the authentication process of S54 performs authentication by comparing various attributes of the public key included in the public key certificate with predetermined conditions that are acceptable for the attributes.

FIG. 9 is a sequence diagram illustrating a processing process in which the client proxy device 100 authenticates the public key certificate issued by the server device 400.
Unlike FIG. 8, there is a case where it is desired to manage the authentication policy for each client terminal 300 individually. FIG. 6 is a sequence diagram when such authentication processing is performed in the client proxy device 100 that proxy the transmission processing of the client terminal 300.

  When the client terminal 300 transmits a connection request command to the server device 400 (S10) and the server device 400 generates the public key S / secret key S (S12), the server device 400 obtains the public key certificate of the public key S. The data is transmitted to the client terminal 300 (S14). The public key acquisition unit 224 of the server proxy device 200 acquires the public key certificate. However, in the case of the processing shown in the figure, the network interface processing unit 230 of the server proxy device 200 receives the public key certificate from the client proxy device 100. (S70). The public key authentication unit 170 of the client proxy device 100 determines whether the certificate authority of the public key S corresponds to one of the certificate authorities registered in its root certificate (S72). Note that the root certificate referred to at this time may be the same as the root certificate of the client terminal 300. If the root certificate of the client proxy device 100 and the root certificate of the client terminal 300 are the same, the client proxy device 100 can apply the authentication policy of the client terminal 300 as it is.

  If the authentication is successful (Y in S74), the public key generation unit 162 of the client proxy device 100 generates a public key P and a private key P (S13). The public key issuing unit 126 transmits a public key certificate including the public key P to the client terminal 300 (S15). The subsequent processing is as described with reference to FIG.

  On the other hand, if the authentication fails (N in S74), the user interface processing unit 110 of the client proxy device 100 displays a warning screen indicating the authentication failure (S76). The user of the client proxy device 100 selects whether or not to allow at his / her own risk while displaying the warning screen (S78). If permitted (Y in S78), the process proceeds to S13. If not permitted (N in S78), the process ends without the public key certificate being issued from the client proxy device 100.

  According to such a processing method, the authentication policy for each client terminal 300 can be applied by the client proxy device 100. Also in the authentication process of S72, the validity period of the public key S and the ID of the server device 400 are determined. Either the authentication process on the reception side shown in FIG. 8 or the authentication process on the transmission side shown in FIG. 9 may be applied, or double authentication processing is performed by performing the authentication process on both the reception side and the transmission side. May be executed.

The communication proxy system 310 in the present embodiment has been described above.
As shown in the present embodiment, when the client terminal 300 and the client proxy device 100 agree on the rules regarding encryption, a series of processes of decryption, compression, and re-encryption of <secret data> by the client proxy device 100 Can be realized. By such processing, the two purposes of increasing the compression rate of the confidential data passing through the communication network 350 and ensuring the communication security are achieved. Further, by agreeing on encryption rules between the client proxy device 100 and the server proxy device 200, and between the server proxy device 200 and the server device 400, the server proxy device 200 decrypts and expands <[secret data]>. A series of processes called re-encryption can be realized. In particular, communication security from the server proxy device 200 to the server device 400 can be ensured by the server proxy device 200 and the server device 400 agreeing on encryption rules.

The server proxy device 200 intercepts the public key S generated by the server device 400 and passes the <common key Q> to the server device 400 instead of the <common key C>. Also, instead of <confidential data> encrypted with the common key C, <confidential data> encrypted with the common key Q is passed. For this reason, the processing of the server device 400 does not have to deviate from the framework of the SSL protocol.
The client proxy device 100 issues a unique public key P to the client terminal 300 instead of the public key S. For this reason, the processing of the client terminal 300 does not have to deviate from the framework of the SSL protocol.
Thus, even if the communication proxy system 310 is introduced into an existing SSL-compatible communication system, no particular change occurs in the processing process of the client terminal 300 or the server device 400. Therefore, the communication proxy system 310 of the present embodiment has an advantage that it can be easily introduced into an existing SSL compatible communication system. SSL is an already widely used communication protocol. By introducing the communication proxy system 310 shown in this embodiment, the transmission efficiency of the existing SSL communication system can be improved.
The communication network 350 may be a wired communication network, but the communication method shown in the present embodiment is particularly effective when it includes a wireless communication network in which packet loss is likely to occur.

When the client terminal 300 transmits <confidential data> encrypted with the common key C according to the SSL mechanism, the client proxy device 100 intercepts the <confidential data> and performs a series of processes of decryption / compression / encryption. Is sent to the server device 400. Regardless of the presence or absence of the client proxy device 100, the client terminal 300 does not change sending <confidential data> with the server device 400 as a destination. Therefore, even if the client proxy device 100 is introduced, it is not necessary to change the setting of the client terminal 300. The same applies to the server proxy device 200 when <secret data> is transmitted from the server device 400 to the client terminal 300.
The client proxy device 100 may be a software module installed in the client terminal 300. In this case, the client proxy device 100 is formed as a part of the function of the client terminal 300. (Hereinafter, when it is clarified that it is a software module, it will be called a “client proxy module”). The client proxy module intercepts the <secret data> encrypted by the application software executed on the client terminal 300 with the common key C, and performs a series of processes such as decryption / compression / encryption, and then transmits them to the server apparatus 400 May be. Regardless of the presence / absence of the client proxy module, the application software that is the transmission subject does not change sending <secret data> with the server device 400 as the destination. The same applies to the case where the server proxy device 200 is formed as a software module and <confidential data> is transmitted from the server device 400 to the client terminal 300.
The client terminal 300 may transmit data with the client proxy device 100 instead of the server device 400 as a direct destination. For example, the client terminal 300 transmits <secret data> including the ID of the destination server apparatus 400 to the client proxy apparatus 100, and after the client proxy apparatus 100 performs address resolution using the server ID, the corresponding server apparatus 400 <Confidential data> may be transmitted. According to such a processing method, the destination itself can be concealed between the client terminal 300 and the client proxy device 100. The same applies to the downstream transmission of the pattern B.

  The client proxy device 100 registers the certificate authority of the public key P in the root certificate of the client terminal 300. Accordingly, since the client proxy device 100 automatically authenticates the public key P issued by the server device 400, the processing after S16 in FIG. 7 can proceed smoothly. In this embodiment, each time a connection request command from the client terminal 300 is detected, a public key P and a secret key P are generated as a pair. Therefore, the communication security between the client proxy device 100 and the client terminal 300 is more robust.

  The server proxy device 200 may have an authentication function for the public key S issued by the server device 400. If the authentication policy of each client proxy device 100 is applied to the server proxy device 200, the public key certificates issued by the plurality of server devices 400 can be centrally authenticated based on the authentication policy of the client proxy device 100. If the public key S is not authenticated or allowed, the client proxy device 100 does not issue the public key P. Therefore, it is possible to effectively suppress transmission of confidential data to the server apparatus 400 that does not conform to the authentication policy of the server proxy apparatus 200.

  The client proxy device 100 may have an authentication function for the public key S issued by the server device 400. Accordingly, each client proxy device 100 can manage the authentication policy for each user. Further, the client proxy device 100 can apply the authentication policy of the client terminal 300 as it is by sharing the root certificate with the client terminal 300.

It should be noted that the processing process when the secret data is encrypted with the public key instead of the common key is also added.
In the processing of FIG. 7, only the processing of S10, S12, S13, S14, and S15 is the execution target. Thus, the client terminal 300 holds the public key P, the client proxy device 100 holds the secret key P, the server proxy device 200 holds the public key S, and the server device 400 holds the secret key S.
Next, the process of FIG. 4 is changed as follows. The client terminal 300 encrypts the secret data with the public key P (S24), and transmits <secret data> to the client proxy device 100 (S26). The client proxy device 100 decrypts the <secret data> with the secret key P (S36), compresses it (S38), encrypts it with the common key P (S40), and sends it to the server proxy device 200 (S42). The server proxy device 200 decrypts <[secret data]> with the common key P (S44), expands it (S46), encrypts it with the public key S (S48), and transmits it (S50). The server apparatus 400 decrypts this <secret data> with the secret key S.
The processing content similar to the compression processing shown in the present embodiment can be applied to such a processing method.

  In the above, this invention was demonstrated based on the Example. The embodiments are exemplifications, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. .

The first data processing device described in the claims corresponds to the client terminal 300 in the present embodiment, and the second data processing device corresponds to the server device 400. The first communication proxy device according to the claims corresponds to the client proxy device 100 and the second communication proxy device corresponds to the server proxy device 200 in the pattern A of this embodiment. In the pattern B, the first communication proxy device corresponds to the server proxy device 200, and the second communication proxy device corresponds to the client proxy device 100.
The encryption rule described in the claims corresponds to the common key P secretly shared between the client proxy device 100 and the server proxy device 200 and its encryption method.
In addition, it should be understood by those skilled in the art that the functions to be fulfilled by the constituent elements described in the claims are realized by the individual functional blocks shown in the present embodiment or their linkage. .

It is a sequence diagram for demonstrating the structure of a general SSL. It is a hardware block diagram of the communication proxy system in a present Example. It is a sequence diagram at the time of adding the data compression process by a communication proxy system to the SSL communication process of FIG. It is a sequence diagram which shows the data compression process in a present Example. It is a functional block diagram of a client proxy device. It is a functional block diagram of a server proxy device. It is a sequence diagram which shows the process for the key sharing in a present Example. It is a sequence diagram which shows the process in which a server proxy apparatus authenticates the public key certificate which a server apparatus issues. It is a sequence diagram which shows the process in which a client proxy apparatus authenticates the public key certificate which a server apparatus issues.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 Client proxy apparatus, 110 User interface processing part, 120 Proxy interface processing part, 122 Transmission data acquisition part, 124 Common key acquisition part, 126 Public key issuing part, 130 Network interface processing part, 132 Data transmission part, 140 Data processing part , 150 compression processing unit, 152 transmission data decryption unit, 154 transmission data compression unit, 156 transmission data encryption unit, 160 key processing unit, 162 public key generation unit, 164 common key decryption unit, 166 connection request detection unit, 168 authentication Station registration unit, 170 public key authentication unit, 180 key data holding unit, 200 server proxy device, 210 user interface processing unit, 220 proxy interface processing unit, 222 data transfer unit, 224 public key acquisition unit, 2 26 common key issuing unit, 230 network interface processing unit, 232 data receiving unit, 240 data processing unit, 250 expansion processing unit, 252 reception data decryption unit, 254 reception data expansion unit, 256 reception data encryption unit, 260 key processing unit 262 common key generation unit, 264 common key encryption unit, 266 public key authentication unit, 280 key data holding unit, 300 client terminal, 310 communication proxy system, 350 communication network, 400 server device.

Claims (7)

The first data processing device is added to a system for transmitting encrypted data from the first data processing device to the second data processing device based on a public key issued by the second data processing device. A first communication proxy device proxying the transmission processing of the second data processing device and a second communication proxy device proxying the reception processing of the second data processing device,
The first communication proxy device is:
A public key issuing unit that issues the public key of the first communication proxy device to the first data processing device instead of the public key of the second data processing device;
A common key acquisition unit that acquires a common key encrypted with the public key of the first communication proxy device from the first data processing device;
A common key decryption unit for decrypting the encrypted common key with the secret key of the first communication proxy device;
A transmission data acquisition unit for acquiring data encrypted by the common key from the first data processing device;
A transmission data decryption unit for decrypting the acquired data with the common key;
A data compression unit for compressing the decoded data by a predetermined compression method;
A transmission data encryption unit for encrypting the compressed data according to an encryption rule negotiated between the first communication proxy device and the second communication proxy device;
A data transmission unit that transmits the encrypted data to the second communication proxy device,
The second communication proxy device is:
A data receiving unit for receiving data encrypted according to the encryption rule from the first communication proxy device;
A received data decryption unit for decrypting the received data according to the encryption rule;
A data expansion unit that expands the decrypted data by a decompression method corresponding to the compression method;
A data transfer unit for transferring the expanded data to the second data processing device;
A communication proxy system comprising: The second communication proxy device is:
A public key acquisition unit for acquiring a public key issued by the second data processing device;
A common key generation unit for generating a common key for use between the second communication proxy device and the second data processing device;
A common key transmission unit that encrypts the generated common key with the acquired public key and transmits the encrypted common key to the second data processing device;
A received data encryption unit that encrypts the expanded data with the generated common key;
The communication proxy system according to claim 1, wherein the data transfer unit transfers the expanded data to the second data processing apparatus in an encrypted state. The first communication proxy device is:
A certificate authority registration unit for registering the certificate authority of the public key issued by the first communication proxy device as a certificate authority acceptable by the first data processing device;
The communication proxy system according to claim 1, further comprising: The first communication proxy device is:
A connection request detection unit that detects a connection request command that the first data processing device transmits to the second data processing device;
4. The communication proxy according to claim 1, wherein the public key issuing unit issues a new public key to the first data processing device every time the connection request command is detected. system. The first data processing apparatus is added to a system for transmitting encrypted data from the second data processing apparatus to the first data processing apparatus based on a public key issued by a second data processing apparatus. A first communication proxy device proxying the reception process and a second communication proxy device proxying the transmission process of the second data processing device,
The first communication proxy device is:
A public key issuing unit that issues the public key of the first communication proxy device to the first data processing device instead of the public key of the second data processing device;
A common key acquisition unit that acquires a first common key encrypted with the public key of the first communication proxy device from the first data processing device;
A common key decryption unit for decrypting the encrypted first common key with a secret key of the first communication proxy device,
The second communication proxy device is:
A public key acquisition unit for acquiring a public key issued by the second data processing device;
A common key generation unit for generating a second common key for use between the second communication proxy device and the second data processing device;
A common key transmission unit that encrypts the generated second common key with the acquired public key and transmits the encrypted second common key to the second data processing device;
A transmission data acquisition unit for acquiring data encrypted by the second common key from the second data processing device;
A transmission data decryption unit for decrypting the acquired data with the second common key;
A data compression unit for compressing the decoded data by a predetermined compression method;
A transmission data encryption unit for encrypting the compressed data according to an encryption rule negotiated between the second communication proxy device and the first communication proxy device;
A data transmission unit that transmits the encrypted data to the first communication proxy device;
The first communication proxy device is:
A data receiving unit that receives data encrypted by the encryption rule from the second communication proxy device;
A received data decryption unit for decrypting the received data according to the encryption rule;
A data expansion unit that expands the decrypted data by a decompression method corresponding to the compression method;
A data transfer unit that encrypts the expanded data with the first common key and transfers the encrypted data to the second data processing device;
A communication proxy system comprising: The first data processing device is added to a system for transmitting encrypted data from the first data processing device to the second data processing device based on a public key issued by the second data processing device. A device that performs the transmission processing of
A public key issuing unit that issues the public key of the first communication proxy device to the first data processing device instead of the public key of the second data processing device;
A common key acquisition unit that acquires a common key encrypted with the public key of the first communication proxy device from the first data processing device;
A common key decryption unit for decrypting the encrypted common key with the secret key of the first communication proxy device;
A transmission data acquisition unit for acquiring data encrypted by the common key from the first data processing device;
A transmission data decryption unit for decrypting the acquired data with the common key;
A data compression unit for compressing the decoded data by a predetermined compression method;
A transmission data encryption unit that encrypts the compressed data according to a predetermined encryption rule that can be decrypted on the second data processing device side;
A data transmission unit configured to transmit data encrypted according to the predetermined encryption rule with the second data processing device as a transmission destination;
A communication proxy device comprising: Transmission of the first data processing apparatus in a system for transmitting encrypted data from the first data processing apparatus to the second data processing apparatus based on a public key issued by the second data processing apparatus A computer program representing the processing,
A function of issuing a unique public key to the first data processing device instead of the public key of the second data processing device;
A function of acquiring a common key encrypted with the unique public key from the first data processing device;
A function of decrypting the encrypted common key with a secret key corresponding to the unique public key;
A function of acquiring data encrypted by the common key from the first data processing device;
A function of decrypting the acquired data with the common key;
A function of compressing the decrypted data by a predetermined compression method;
A function of encrypting the compressed data according to a predetermined encryption rule that can be decrypted on the second data processing device side;
A function of transmitting data encrypted according to the predetermined encryption rule with the second data processing device as a transmission destination;
Communication proxy program characterized by causing a computer to exhibit

Images