JPH07250250A - Terminal equipment for cipher communication - Google Patents

Abstract

PURPOSE:To provide a terminal equipment for cipher communication with which cipher communication can be conducted even when a secret cryptographic key is not previously decided or any wrong secret cryptographic key is registered. CONSTITUTION:In the case of cipher communication, first of all, it is decided whether the secret cryptographic key is stored or not (S4) and when it is discriminated that the secret cryptographic key is stored, it is discriminated whether received ciphered data can be deciphered by that secret cryptographic key or not (S5). As a result, when it is discriminated that those data can not be deciphered, it is regarded that the wrong secret cryptographic key is registered, and the received ciphered data are stored in a cipher box area provided at a memory (S7). On the other hand, when it is discriminated in the S4 that the secret cryptographic key is not stored, it is regarded that the secret cryptographic key is not previously decided, and the received ciphered data are stored in the cipher box area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal device for encrypted communication, and more particularly to improvement of a reception processing method in encrypted communication.

[0002]

2. Description of the Related Art Conventionally, in the field of communication, from the viewpoint of maintaining confidentiality of communication data, encryption processing has been performed on the communication data. For example, in facsimile communication in which original image data corresponding to an original is transmitted and received, in order to maintain confidentiality of the original image data which is communication data, the original image data is subjected to encryption processing.

As one of the methods of encryption processing of original image data, there is one using a so-called secret encryption key. Specifically, the original image data is subjected to a predetermined logical operation using a secret encryption key, whereby encrypted data completely different from the original image data is created. On the other hand, the decryption process for restoring the encrypted data to the original image data is achieved by subjecting the encrypted data to a predetermined logical operation using the secret encryption key.

As described above, in the encryption processing and the decryption processing,
A common secret encryption key is required. Therefore, in the past,
It is said that a secret encryption key is preliminarily agreed between the transmitting side and the receiving side of the encrypted communication, and the secret secret key thus agreed is registered in advance in the non-volatile memories provided in the transmitting side terminal device and the receiving side terminal device, respectively. The method is adopted.

[0005]

However, if the secret encryption key cannot be negotiated in advance, such as when the other party is absent, encrypted communication cannot be executed. Further, even if the secret encryption key is agreed in advance, if either the transmitting side or the receiving side registers the wrong secret encryption key, the encrypted communication cannot be executed. Therefore, there is a problem that the user interface is very bad.

Therefore, an object of the present invention is to solve the above-mentioned technical problems and to provide a terminal device for encrypted communication which can execute encrypted communication without preliminarily negotiating a secret encryption key. Another object of the present invention is to provide a terminal device for encrypted communication that can execute encrypted communication even if a wrong secret encryption key is registered.

[0007]

A terminal device for cipher communication according to claim 1 for achieving the above object, is a receiving means for receiving data from a predetermined communication line, and a receiving means for receiving the data. Data discriminating means for discriminating whether or not the generated data is encrypted data produced by subjecting the original image data to an encryption process using a predetermined secret encryption key; and the receiving means by the data discriminating means. When it is determined that the received data is encrypted data, the decryption determination unit that determines whether the encrypted data can be decrypted, and the result of the determination by the decryption determination unit that the data cannot be decrypted And a data storage unit that stores the received encrypted data when the determination is made.

The terminal device for encrypted communication according to claim 2 further includes an encryption key storage means in which a secret encryption key is stored in advance, and the decipherability determination means is the encryption received by the reception means. The predetermined secret encryption key used to create the encrypted data is compared with the secret encryption key stored in the encryption key storage means, and if they do not match, it is determined that the decryption is not possible. To do.

Further, in the terminal device for encrypted communication according to claim 3, the encrypted data is stored in the data storage means in response to the encrypted data stored in the data storage means. Is further included in the report output means for outputting the reception report.

[0010]

In the structure according to the above-mentioned claim 1, when the receiving means receives the data, it is judged whether or not the received data is the encrypted data. As a result, when it is determined that it is encrypted data, it is determined whether or not this encrypted data can be decrypted. That is, for example, claim 2
As in the configuration described, the predetermined secret encryption key used to create the encrypted data is compared with the secret encryption key stored in the encryption key storage means, and if they do not match, it is determined that the decryption is not possible. It Then, when it is determined that the data cannot be decrypted, the received encrypted data is stored in the data storage means.

As described above, even when undeciphered encrypted data is received, the encrypted data is stored, so that the secret encryption key is not agreed in advance or the wrong secret encryption key is stored. In this case, encrypted data can be transmitted and received, that is, encrypted communication can be achieved.
When the encrypted data is stored, a reception report indicating that the encrypted data is stored may be output as in the configuration according to claim 3. With this configuration, the receiving side can easily and quickly confirm that the undecrypted encrypted data is stored.

[0012]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the electrical configuration of a facsimile apparatus according to an embodiment of the present invention.
This facsimile apparatus includes a reading unit 1 that optically reads a document to be transmitted and outputs original image data. The original image data output from the reading unit 1 is given to the image processing unit 2 and subjected to predetermined image processing. The original image data subjected to the image processing is given to a transmission function unit 4 via a control unit 3 which functions as a data discriminating means, a decipherability judging means, etc., and is transmitted to an MH (Modified Huffman), MR.
(Modified READ, READ: Relative Element Address De
Signate) etc. are subjected to compression coding necessary for facsimile communication. The original image data that has been subjected to this compression coding is given to the modem 5 via the control unit 3. Further, when performing encrypted communication, in the encrypted communication device 6, the compression-encoded original image data is encrypted and encrypted data is created using a predetermined secret encryption key, and the created encryption is performed. The converted data is given to the modem 5. The compression-encoded original image data or encrypted data is transferred to the network controller (NC
U) 7 to the public telephone line 8.

This facsimile apparatus also comprises a memory 9 composed of a DRAM or an SRAM which functions as a data storage means, an encryption key storage means and the like. The memory 9 stores an encryption key table 9a as shown in FIG. More specifically, necessary for decryption of the encryption and later, multiple private encryption key K ₁ that is negotiated in advance between a plurality of communication destination, K _2, K _3, · ·
., K _n (hereinafter collectively referred to as “secret encryption key K”) are table numbers “00”, “01”, “02”, ... Corresponding to the facsimile numbers of the respective communication destinations.
It is stored in a one-to-one correspondence with "n".

Further, in the memory 9, as shown in FIG.
An encryption box area 9b is provided. As will be described later, the cipher box area 9b is provided to temporarily store the unencrypted encrypted data when the encrypted data is received. The facsimile machine further includes an operation unit 10. The operation unit 10 includes a ten-key 10a for a user to input a destination facsimile number, a start key 10b for inputting a start signal of a facsimile apparatus, an encrypted communication key 10c for instructing encrypted communication, and an output mode. A function key 10d for setting the operation mode of the facsimile machine such as a secret encryption key set mode and the like is arranged. Note that the types of keys and the like described above are examples, and keys may be added or keys may be changed as necessary.

When the facsimile apparatus shown in FIG. 1 receives data, the data is given to the modem 5 functioning as a receiving means via the NCU 7. When the received data is simply compression-coded original image data, that is, in the case of normal facsimile communication, the received original image data is demodulated by the modem 5 and then decoded (decompressed) by the reception function unit 11. ) Is performed, and the original image data is restored. Thereafter, the original original image data is given to the recording unit 12 that functions as a report output unit, and the recording unit 1
The transmission original is reproduced by being printed on the paper in 2.

On the other hand, when the received data is encrypted data, that is, in the case of encrypted communication, the received encrypted data is demodulated by the modem 5 and then decrypted by the encrypted communication device 6. To be done. Then, in the receiving function unit 11, the original image data is decrypted to restore the original image data in the same manner as described above, and then the recording unit 12 prints the original image data on the paper to reproduce the transmitted original document.

FIG. 3 is a flow chart showing the receiving operation in the facsimile apparatus. In the facsimile machine, when the line with the transmitting facsimile machine is connected, first of all, the facsimile machine with which the line is connected is specified (step S1). This identification is performed by a calling terminal identification signal (CIG: Calling Subscriber Identifier) transmitted prior to the transmission of the original image data or the encrypted data.
The table number corresponding to the facsimile number included in the certification) is used.

Next, in the facsimile machine, it is judged whether or not the communication is cipher communication (step S2). This determination is made by a non-standard function setting signal (NSS: Non-Standard facilitie) transmitted prior to transmission of original image data or encrypted data.
s Set-up) is performed based on whether a flag indicating whether the communication is encrypted communication is set or not. As a result of the above determination,
If the flag is not set, it is determined that the facsimile communication is normal, and the normal cipher reception process is performed (step S3). On the other hand, if the flag is set, it is determined to be encrypted communication.

When it is determined that the encryption communication is performed, in response thereto, it is determined whether the secret encryption key K is stored in association with the same table number included in the CIG. (Step S4). As a result, when the secret encryption key K is stored, the stored secret encryption key K is read out, and it is determined whether or not the read secret encryption key K can be decrypted (step S5). ). On the other hand, when the secret encryption key K is not stored, it is considered that the secret encryption key is not agreed with the sender in advance, and the process directly proceeds to step S7 described later.

Next, the discrimination processing in the above step S5 will be specifically described. First, the above-mentioned read secret encryption key K is applied to a decryption process for n (for example, n = 1 to 5) lines from the head of the received encrypted data. Here, if the secret encryption key applied when the encrypted data was created in the sending facsimile machine and the read secret encryption key K match, the result of the decryption process is output. The original image data has the number of bits per line according to the transmitted original. Specifically, the transmitted original is A
In the case of the 4th edition, there are 1728 bits per line.

On the other hand, a secret encryption key applied when encrypted data is created in the sending facsimile machine,
If the read secret encryption key K does not match,
The output original image data does not have 1728 dots per line even if the transmitted original is A4 size. That is, it is determined whether or not the encrypted data can be decrypted based on the number of bits of the output original image data.

If the result of the determination in step S5 is that it is decipherable, normal document output processing such as decoding / recording is executed (step S6). On the other hand, if it is determined that it cannot be decrypted, it is considered that either the sender or the receiver uses the wrong secret encryption key,
The received encrypted data is stored in the cipher box area 9b of the memory 9 (step S7). In response to this, a reception report indicating that the encrypted data is stored in the encryption box area 9b is output from the recording unit 12 (step S7). FIG. 4 shows a specific example of the reception report.

In this way, when the secret encryption key is not agreed in advance and when the wrong secret encryption key is used, the received encrypted data is the encrypted box area 9
Since it is stored in b, encrypted communication can be achieved even in the above case. Also, since the reception report is output in response to the encrypted data being stored in the encryption box area 9b, the user can easily and quickly confirm that the encrypted data has been received.

By the way, after the reception report confirms that the encrypted data has been received, the transmission original can be reproduced based on the received encrypted data. Therefore, the document output process will be described next.
FIG. 5 is a flow chart showing a document output process in the facsimile apparatus. In order to reproduce the transmission original based on the encrypted data stored in the encryption box area 9b, it is necessary to set the operation mode of the facsimile apparatus to the output mode. Function key 1 by user
When 0d is operated to set the operation mode to the output mode (step P1), the control unit 3 causes the encryption box area 9b
It is monitored whether or not encrypted data is stored in (step P2). As a result, if the encrypted data is not stored, this output mode is terminated, while if the encrypted data is stored, it is determined whether or not the secret encryption key is next input (step P3). .

The encrypted data is stored in the encryption box area 9b because the secret encryption key K necessary for decrypting the encrypted data is not stored in the memory 9 or an incorrect secret encryption key is stored. This is the case where K is stored in the memory 9. Therefore, an accurate secret encryption key is required to reproduce the transmitted document based on the stored encrypted data. This accurate private encryption key can be obtained, for example, by negotiating with the sender after outputting the reception report.

When the user sets the operation mode of the facsimile apparatus to the secret cryptographic key set mode for inputting the secret cryptographic key, and further inputs the secret cryptographic key, a cryptogram that can be decrypted by the input secret cryptographic key. It is determined whether the encoded data is stored (step P4). This determination method is the same as that described with reference to FIG. If the result of this determination is that no decipherable encrypted data has been stored, this output operation ends. On the other hand, if the decipherable encrypted data is stored, the encrypted data is decrypted using the input secret encryption key (step P5), and after decryption, the recording unit 12 prints it on the paper. And the transmitted document is reproduced (step P
6). After that, the process returns to step P4, and the above step P3
The above process is repeated until there is no encrypted data that can be decrypted with the private encryption key input in step.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above-described embodiment, the facsimile device is described as an example of the terminal device, but the present invention can be applied to other terminal devices such as a personal computer and a word processor, and also to various other terminal devices capable of encrypted communication. Can be widely applied.

Further, in the above embodiment, the original image data was described as an example of the data to be transmitted, but the present invention can be applied when transmitting data other than the original image data. Other various design changes can be made within the scope described in the claims.

[0029]

As described above, according to the terminal device for encrypted communication according to the first or second aspect, encrypted data that cannot be decrypted is stored. Therefore, when the secret encryption key is not agreed in advance. Even if the wrong secret encryption key is registered, encrypted communication can be achieved. Therefore, the user interface can be improved.

Further, according to the terminal device for encrypted communication of claim 3, since the reception report is output when the undeciphered encrypted data is received, it is easy to store the encrypted data. It can be confirmed quickly and quickly. Therefore, the subsequent treatment can be performed appropriately and quickly.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a facsimile apparatus according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a configuration of a memory which constitutes a part of the facsimile device.

FIG. 3 is a flowchart showing a receiving operation in the facsimile device.

FIG. 4 is a diagram showing an example of a reception report output when encrypted data that cannot be decrypted is received by the facsimile device.

FIG. 5 is a flowchart showing a document output process in the facsimile device.

[Explanation of symbols]

 3 control unit 5 modem 6 cryptographic communication device 9 memory 12 recording unit

Claims (3)

[Claims] 1. Receiving means for receiving data from a predetermined communication line, and data received by this receiving means is created by subjecting original image data to encryption processing using a predetermined secret encryption key. Data discriminating means for discriminating whether or not the data is encrypted data, and when the data discriminating means discriminates that the data received by the receiving means is the encrypted data,
Decryption possibility determining means for determining whether or not the encrypted data can be decrypted, and when it is determined that the decryption is impossible as a result of the determination by the decryption possibility determining means, the received encrypted data is stored. A terminal device for encrypted communication, comprising: a data storage unit for storing the data. 2. A cryptographic key storage means for storing a secret cryptographic key in advance, wherein the decipherability judging means is a predetermined secret cryptographic key used for creating the encrypted data received by the receiving means. 2. The terminal device for encrypted communication according to claim 1, wherein the secret encryption key stored in the encryption key storage means is compared, and if they do not match, it is determined that decryption cannot be performed. 3. A report output means for outputting a reception report indicating that the encrypted data is stored in the data storage means in response to the encrypted data stored in the data storage means. Claim 1 characterized by the above-mentioned.
Alternatively, the terminal device for the encrypted communication described in 2.