JPH0313139A - Security modem system - Google Patents

Abstract

PURPOSE:To secure safety even when a password is stolen by ciphering transmission data and transmitting the data according to a ciphering system designated by an index number corresponding to the password. CONSTITUTION:When the password is received, a control part 6 retrieves a table 7 for memory and investigates whether the received password is coincident with the password registered to this table 7 for memory or not. When both passwords are coincident, the control part 6 reads the index number corresponding to this password from the table 7 for memory and applies this index number as a code number, which designates the ciphering system, to a ciphering part 2. According to this code number, the data to be inputted from a terminal equipment T is ciphered by the ciphering part 2 and outputted to a modulation/ demodulation part 3. Thus, since the contents of communication are ciphered even when the password is stolen, the data are not illegally received.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a security modem system for performing secure data communication in a modem device that performs data communication via a switched line.

[Prior Art] Conventionally, in a modem device that performs data communication via a switched line, the following security modem methods have been used to ensure safe data communication by prohibiting access by only authorized users. Two methods are common as shown.

■The modem device on the terminal side calls the modem device on the center side and sends the password, and the modem device on the center side checks the received password and starts communication only if this password matches the password registered in advance. Permitted password check method: - The modem device on the terminal side calls the modem device on the center side, sends the password, and then disconnects the line. Then, the modem device on the center side is registered in advance in accordance with the password, and dials the station number of the modem device on the terminal side to call the modem device on the terminal side again.

[Problems to be Solved by the Invention] Among the conventional security modem systems described above, the former password check system has the disadvantage that security cannot be ensured if the password is stolen by a third party. In addition, in the latter callback method, the call is made by dialing the pre-registered area number of the modem device on the terminal side, so if the modem device on the terminal side is moved, the area number of the modem device on the terminal side will change. Therefore, there was a drawback that this callback method could not be used.

Additionally, these methods do not include encryption functions;
There was a problem in that the protection of the contents of data communication was weak.

[Means for Solving the Problems] In the security modem system of the present invention, a modem device is provided with a storage table that stores a plurality of passwords and index numbers corresponding to each password, and the index numbers are used to encrypt data. You can now specify the encryption method to encode or decrypt.

[Operation] When the password received from the transmitting terminal device matches the password registered in the storage table, the index number corresponding to this password is read from the storage table. Then, according to the encryption method specified by this index number, the transmitted data is encrypted and transmitted to the transmitting terminal device, and the received data from the transmitting terminal device is decrypted and received.

[Implementation! 4] Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a modem device in one embodiment of the security modem system of the present invention, and FIG. 2 is a sequence diagram showing the communication procedure of the modem device in the same embodiment.

In FIG. 1, a modem device 10 is connected to a terminal device T such as a personal computer via an input/output port 1. As shown in FIG. 2 encrypts data input from the terminal device T via the input/output port 1 according to a specified encryption method and outputs the encrypted data to the modem 3;
This is an encryption unit that decrypts encrypted data that is input from the input/output port 1 and outputs it to the terminal device T via the data input/output port 1. The modulation/demodulation section 3 is connected to the encryption section 2 and the network control device (hereinafter N
The NCU 4 is connected to the switching network N via the switching circuit connection terminal 5, and controls the connection with the switching network N. This is what we do. 6 is a control section, which includes an encryption section 2, a modulation/demodulation section 3.
The storage table 7, which controls the storage table 7 and performs the operations described later, stores a plurality of passwords and index numbers corresponding to the plurality of passwords, that is,
A number specifying the encryption method is stored.

It is assumed that a modem device and a terminal device similar to the modem device 10 and terminal device T described above are disposed opposite to each other via a switching network N, and communication is performed between them.

Next, the operation will be explained with reference to the sequence diagram shown in FIG.

A transmission side modem device (not shown) arranged opposite to this modem device ff1o connects to a switching network and a switching circuit connecting terminal 5. And when there is an incoming call via NCU4 (Figure 2 (a))
, the control unit 6 controls the modulation/demodulation unit 3 to perform handshake and establish communication (FIG. 2(b)).

Subsequently, upon receiving the password from the transmitting modem device (FIG. 2(c)), the control unit 6 searches the storage table 7 and finds that the received password is registered in this storage table 7. Check whether it matches the password.

If the received password matches the password registered in the storage table 7, the control unit 6 reads the index number corresponding to this password from the storage table 7, and converts this index number into a code number specifying the encryption method. The data is then sent to the encryption unit 2. According to this code number, the encryption unit 2 encrypts the data input from the terminal device T via the data boat 1 and outputs it to the modulation/demodulation unit 3, and also decodes the received data input from the modulation/demodulation unit 3 and decodes the data input from the data boat 1. It is output to the terminal device T via. In this way, online communication is performed (FIG. 2(d)).

In contrast, the received password is stored in the memory table 7.
If the password does not match the password registered in , the control unit 6 determines that the access from the modem device on the sending side is unauthorized access, disconnects the line, and rejects the communication.

As described above, when online communication is performed between both modem devices, encryption and decryption are performed by both modem devices based on the encryption method specified by the index number corresponding to the password. Therefore, unless the encryption methods specified by the index numbers match in both modem devices, normal communication cannot occur.

In other words, it is impossible to perform normal encryption and decryption unless the password stored in the storage table 7 and the encryption method corresponding to this password match in both modem devices 10 attempting to communicate. Become.

[Effects of the Invention] As explained above, in the security modem system of the present invention, when the password received from the transmitting terminal device matches the password registered in the storage table, the index number corresponding to this password is Read from storage table. Then, according to the encryption method specified by this index number, the transmitted data is encrypted and transmitted to the transmitting terminal device, and the received data from the transmitting terminal device is decrypted and received. Therefore, unless the passwords and the encryption methods corresponding to these passwords match between the terminal devices that are attempting to communicate, it is not possible to communicate between the terminal devices.

Therefore, unlike conventional password checking methods, even if your password is stolen by a third party, the communication content is encrypted according to a predetermined encryption method, so data can be obtained illegally. The effect is that it cannot be done. Furthermore, unlike the conventional callback method, there is an advantage that the terminal can communicate while moving because it is not restricted by the station number of the terminal device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a modem device according to an embodiment of the present invention, and FIG. 2 is a sequence diagram of the same embodiment. 2...-encryption unit, 6...-control unit, 7... storage table, 10... modem device.

Claims (1)

[Claims] A security modem system for a modem device that performs data communication via a switched line, comprising: providing the modem device with a storage table that stores a plurality of passwords and index numbers corresponding to the respective passwords; If the password received from the sending terminal device matches the password registered in the storage table, the index number corresponding to this password is read from the storage table, and transmission is performed according to the encryption method specified by this index number. A security modem system characterized in that data is encrypted and transmitted to a transmitting terminal device, and data received from the transmitting terminal device is decrypted and received.