JPH05244153A - Digital communication equipment - Google Patents

Abstract

PURPOSE:To provide the subject digital communication equipment which stores plural cipher keys and secures the correspondence between these keys and both incoming subaddress information on the outgoing and incoming modes to automatically select the cipher keys, to simplify the cipher communication with use of the cipher keys, and also to prevent the leakage of the cipher keys. CONSTITUTION:Plural code train information are stored in a memory 11 and at the same time the cipher keys are also stored in the memory 11 in response to these code train information. A control circuit 10 compares the code train information with the incoming subaddress information on both outgoing and incoming modes. If the coincidence is confirmed between both information, the cipher key information corresponding to the coincident code train information is read out of the memory 11. Then a ciphering/decoding circuit 2 ciphers the transmission information and decodes the reception information by means of the cipher keys.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital communication device having a function of preventing communication leakage by encrypting communication contents, and particularly used for a communication line to which incoming sub-address information is sent together with an incoming signal at the time of incoming call. Digital communication device.

[0002]

2. Description of the Related Art Conventionally, a method of encrypting communication contents has been used in order to prevent communication leakage. Many encryption methods have already been devised,
Among these is a method called a secret key cryptosystem. In secret key cryptography, the sender and receiver of information have the same encryption key, the sender uses the encryption key and the encryption algorithm for encryption, and the receiver uses the encryption key and the decryption algorithm for decryption. It is a method to do. The encryption / decryption algorithm of the secret key cryptosystem is FEAL (Fast Data).
Encipherment Algorism: High-speed data encryption algorithm), DES (Data Encryption Standard: US Federal Standard encryption algorithm), etc. have been published, and encryption / decryption can be performed easily by using these algorithms or LSIs incorporating these algorithms. It can be performed.

[0003]

However, in the cryptographic communication using the secret key cryptosystem, the sending side and the receiving side need to know the same cryptographic key before performing the cryptographic communication, and
If a third party knows this encryption key, there is a problem that it is possible to tap the communication. For this reason, when using the secret key cryptosystem, it is important to manage the cryptographic key so as not to leak. On the other hand, when performing encrypted communication with a plurality of parties, many people will share the encryption key if only one encryption key is used. There is a problem that those who are able to eavesdrop on the communication.

In order to solve the problems of the prior art, it is effective to prepare a plurality of encryption keys and use different encryption keys for each partner. However, in order to use a plurality of encryption keys, it is necessary to have a means for selecting an encryption key for each communication partner, and there is a problem that the operation required for performing encrypted communication becomes complicated.

The present invention has been made in view of the above,
The purpose is to store a plurality of encryption keys and to automatically select the encryption key by associating the incoming subaddress information at the time of sending and the incoming subaddress information at the time of receiving with the incoming key. An object of the present invention is to provide a digital communication device which can be used to easily perform encrypted communication and prevent leakage of an encryption key.

[0006]

In order to achieve the above object, a digital communication apparatus of the present invention is a digital communication apparatus connected to a communication line to which incoming subaddress information is transmitted at the time of an incoming call, and a plurality of codes. Code string information storage means for storing string information, encryption key storage means for storing an encryption key corresponding to the code string information, and destination sub-address information corresponding to a telephone number at the time of transmission to the code string information storage means. At the time of outgoing call comparing means for comparing with the stored code string information and at the time of incoming call for comparing the destination sub-address information sent via the communication line at the time of incoming call with the code string information stored in the code string information storing means. If there is a match as a result of the comparison between the comparing means and the comparing means at the time of sending and the comparing means at the time of receiving, the corresponding code string information Using said encryption key information encryption key storage means is stored, it is summarized in that with an encryption / decryption means for performing decryption of the encrypted and receiving information of the transmission information Te.

[0007]

In the digital communication device of the present invention, a plurality of code string information is stored, an encryption key is stored corresponding to the code string information, and the called subaddress information at the time of call origination and reception is stored in the code string. When there is a match between the information and the code string information, the encryption key information corresponding to the matched code string information is used to encrypt the transmission information and decrypt the reception information.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a digital communication apparatus according to the first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a call for converting transmission information into a signal on a communication line for transmission, converting a signal sent through the communication line into reception information, and for making or receiving a call. A network interface circuit for transmitting or receiving a control signal, and 2 is an encryption / decryption circuit for encrypting transmission information and decrypting reception information using an encryption key, which is a general-purpose CPU, ROM, RAM, etc. A codec for converting a digital signal to an analog signal or an analog signal to a digital signal, and 4 for amplifying a signal input from a transmitter or a signal output to a receiver. The communication circuit 5 is a first circuit used for registering code string information and an encryption key corresponding to the code string information.
Function key (registration key of code string information and encryption key), 6 is a second function key (registration key of telephone number and called sub address information) used for registration of telephone number and called sub address information, and 7 is code string information And a third function key group for registering the encryption key corresponding to this code string information and the telephone number and called sub address information, 8 corresponds to the separation between the telephone number and called sub address information, and the code string information and this code string information The fourth function key used to separate the encrypted key, 9 is the code string information, the encryption key corresponding to this code string information, and the telephone number and called subaddress information are registered as number information, and dial input is made when making a call. Dial key to use, 1
Reference numeral 0 is a general-purpose CPU for controlling the operation of the digital communication device, and a control circuit composed of ROM, RAM, etc., 1
Reference numeral 1 is a memory for storing code string information and an encryption key corresponding to the code string information, 12 is a receiver, and 13 is a transmitter.

FIG. 2 is a block diagram showing a digital communication apparatus of the second embodiment in which the memory 11 of the first embodiment shown in FIG. 1 is replaced with an IC card.

In FIG. 2, 1 to 10 and 12 to 13 are the same as those in FIG. 1, and 14 is the reading / reading of the IC card 15.
IC card interface circuit for writing, 15
Is an IC card that stores code string information and an encryption key corresponding to this code string information. A memory card without a built-in CPU can be used instead of the IC card.

Next, the operation of the digital communication device of FIGS. 1 and 2 for registering code string information and an encryption key corresponding to the code string information will be described with reference to the flowchart shown in FIG.

To register the code string information and the encryption key corresponding to the code string information in the digital communication device, the control circuit 10 controls the first function key 5, the third function key group 7, the dial key 9 and the fourth function key 5. Information input by the function key 8 is stored in the memory 1
1 or by writing in the IC card 15. Specifically, the control circuit 10 detects that one of the third function keys 7 has been pressed following the pressing of the first function key 5 (step 110) (step 120),
The number information input by the dial key 9 is written as code string information in the memory area corresponding to the depressed key of the third function key group 7 (step 130),
It is detected that the function key 8 of is pressed (step 14
0), the number information input by the dial key 9 is used as the encryption key, and the writing operation is performed in the area corresponding to the pressed key of the third function key group 7 and different from the storage area of the code string information ( This is possible by finally pressing the first function key 5 (step 150).

Next, with reference to the flow chart shown in FIG. 4, the operation of registering the telephone number and the destination sub-address information in the fourth function key group 8 will be described.

The registration of the telephone number and the destination subaddress information to the digital communication device is performed by the control circuit 10 by the second function key 6, the third function key group 7, the dial key 9 and the fourth function key 8. It can be realized by writing the information to be stored in the memory 11 or the IC card 15. Specifically, the control circuit 10 detects that one of the third function keys 7 has been pressed following the pressing of the second function key 6 (step 210) (step 220), and the dial key The number information input by the dial key 9 is written in the memory area as the telephone number (step 230), and it is detected that the fourth function key 8 is pressed (step 240), and the number information input by the dial key 9 is detected. In the memory area as destination sub-address information (step 25
0), and finally by pressing the second function key 6.

Next, the operation of the digital communication apparatus of the first embodiment shown in FIG. 1 when making a call will be described with reference to the flow chart shown in FIG.

When making a call by inputting the telephone number of the called party and the called sub-address from the digital communication device using the dial keys 9 and the fourth function key 8 (step 310), the control circuit 10 inputs the called call. The code string information that matches the sub-address information is read from the memory 11, and it is compared whether there is the matching code string information (step 34).
0,350). If there is matching code string information, the encryption key registered corresponding to this code string information is stored in the memory 11
From the memory 11 (step 360), and the encryption key read from the memory 11 to the network interface circuit 1 is written to the encryption / decryption circuit 2 (step 370). Then, a calling signal is sent out, and the destination digital communication device as a communication partner responds (steps 380 and 390). When communication is started, the sending signal input from the sending device 13 is transmitted to the communication circuit 4. Is amplified by the codec 3, converted into a digital signal by the codec 3, encrypted by the encryption / decryption circuit 2 using the encryption key written from the control circuit 10, and transmitted to the communication line through the network interface circuit 1. On the other hand, the received information received from the communication line through the network interface circuit 1 is transmitted to the control circuit 10 in the encryption / decryption circuit 2.
The data is decrypted using the encryption key written in the above, converted into an analog signal by the codec 3, amplified by the communication circuit 4, and output as a reception signal from the handset 12 (step 400).

When the telephone number and the destination sub-address information registered in the third function key group 7 are read out to make a call, one of the third function key group 7 is depressed. , The telephone number and the destination subaddress information are designated (step 320), and the telephone number and the destination subaddress information stored in the memory 11 are read (step 330). The read destination sub-address information and the code string information stored in the memory 11 are read and it is compared whether or not there is matching code string information (step 340). The subsequent processing is the same as the above-described processing of steps 350 to 400 and subsequent steps.

If there is no matching code string information in the check in step 350, a calling signal is sent (step 410), the other party's response is awaited, and normal general communication is performed (step 420, 430).

Next, the operation of the digital communication apparatus of the first embodiment shown in FIG. 1 when receiving an incoming call will be described with reference to the flow chart shown in FIG.

When an incoming call is received from the communication line (step 51)
0), the control circuit 10 receives the destination sub-address information notified from the communication line at the time of the incoming call through the network interface circuit 1 (step 520), and searches the memory 11 for the code string information matching the destination sub-address information (step 530, 540) If there is matching code string information, the encryption key stored corresponding to the code string information is read (step 550), and the encryption key read from the memory 11 is sent to the encryption / decryption circuit 2. Write (step 560). Then, the incoming call is answered (step 57).
0), after the communication is started, the same encrypted communication as in step 400 of FIG. 5 is performed (step 580).

If there is no destination sub-address information in the check in step 520, and
If there is no matching code string information in the check of 40, the incoming call is answered (step 590) and normal general communication is performed (step 600).

Cryptographic communication in the digital communication apparatus of the second embodiment shown in FIG. 2 is performed in the same manner as in the first embodiment. The difference between the second embodiment and the first embodiment is that the means for storing the code string information and the encryption key to be registered corresponding to the code string information is the memory 11 to the IC card 15. .. Moreover, a dedicated circuit is required for reading and writing a normal IC card, and this circuit is provided as the IC card interface circuit 14. In the first embodiment, for example, it is necessary to register the encryption key in the digital communication device after the parties performing the encrypted communication directly face each other and exchange the encryption key. There is a risk that the encryption key will be leaked to. On the other hand, in the second embodiment, I
The C card 15 can be carried away from the main body of the digital communication device, and when the parties performing the encrypted communication carry the IC card 15 and face each other, the I
Writing the encryption key to the C card 15 can be realized by using an appropriate IC card writing device. IC
The card enhances the confidentiality of the information stored in the card by the function of the CPU built in the card, and the method of using the IC card not only simplifies the exchange of the encryption key, but also uses the encryption key. It has the advantage of reducing the risk of leakage after replacement. When a memory card is used instead of the IC card, the confidentiality of information is inferior, but the same effect can be obtained in that the encryption key can be easily exchanged.

[0025]

As described above, according to the present invention,
A plurality of code string information is stored, an encryption key is stored corresponding to the code string information, the called sub-address information at the time of call origination and reception is compared with the code string information, and both match. If there is one, the encryption key information corresponding to the matched code string information is used to encrypt the transmission information and decrypt the reception information, so that the encryption key is changed for each communication partner to perform the encrypted communication. Even if one encryption key is known to a third party, it is possible to prevent eavesdropping on encrypted communication with other registered communication partners, greatly improving communication security. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a digital communication device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a digital communication device according to a second embodiment of the present invention.

FIG. 3 is a flowchart showing code string information in the digital communication device shown in FIGS. 1 and 2 and a process of registering an encryption key corresponding to the code string information.

4 is a flowchart showing a process of registering a telephone number and called subaddress information in the digital communication device shown in FIGS. 1 and 2. FIG.

FIG. 5 is a flowchart showing processing at the time of making a call by the digital communication device shown in FIGS. 1 and 2.

FIG. 6 is a flowchart showing a process when the digital communication device shown in FIGS. 1 and 2 receives an incoming call.

[Explanation of symbols]

 1 Network Interface Circuit 2 Encryption / Decryption Circuit 5 First Function Key 6 Second Function Key 7 Third Function Key Group 8 Fourth Function Key 9 Dial Key 10 Control Circuit 11 Memory 15 IC Card

Claims (2)

[Claims] 1. A digital communication device connected to a communication line to which destination sub-address information is transmitted when an incoming call arrives, the code string information storing means storing a plurality of code string information, and corresponding to the code string information. Encryption key storage means for storing an encryption key, transmission time comparing means for comparing destination subaddress information corresponding to a telephone number with code string information stored in the code string information storage means at the time of calling, and communication at the time of incoming call Incoming call comparing means for comparing the incoming subaddress information transmitted via the line with the code string information stored in the code string information storing means, and the result of the comparison in the outgoing call comparing means and the incoming call comparing means, If there is a match, the encryption key information stored in the encryption key storage means corresponding to the matched code string information is used to send the transmission information. A digital communication apparatus comprising: an encryption / decryption means for performing encryption and decryption of received information. 2. The digital communication apparatus according to claim 1, wherein the code string information storage means and the encryption key information storage means are storage means that can be attached to and detached from a main body of the digital communication apparatus.