JPS6051341A - Cipher control method of communication terminal - Google Patents

Abstract

PURPOSE:To prevent the leak of a cipher by updating the cipher at every communication call for every communication destination. CONSTITUTION:When a communication is terminated, a cipher number generating circuit 26 of a terminal 2 is started, and a cipher is generated by, for example, rangom numbers and is sent to a terminal number cipher storage circuit 24. This circuit 24 updates contents of a memory corresponding to a destination terminal 1, with which a terminal 2 comunicates just before the communication is terminated, to said generated cipher. This new cipher is sent to the destination terminal 1 through a cipher transmitting circuit 27. Consequently, the new cipher is used for the next communication between terminals 1 and 2. Thus, even if the cipher used in the preceding communication is deciphered, communication contents are not leaked because another new cipher is used for communication.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication terminal encryption control method applied to a terminal device connected to a general public communication network.

In recent years, in data communications, facsimile communications, and the like, an increasing number of terminals are connected within a general public communication network and communicate with each other without human intervention. If it is necessary to protect the confidentiality of the communication contents in such communication, a method such as determining a code and confirming it at the start of communication is taken. However, with this method, if the encryption is leaked by some means, it is necessary to update all the encryption memory in the terminal, and if the leak is not noticed, the communication contents will also be leaked and you will suffer a big loss. There was a drawback.

Therefore, an object of the present invention is to provide a communication terminal encryption control method that prevents encryption from being easily leaked to others.

In order to achieve the above object, the invention provides a communication terminal with a functional circuit that sends its own terminal number and a functional circuit that receives the other party's terminal number. It is designed to store the code until the next communication with the same terminal, and to check the terminal number sent by the other party at the start of communication with the code stored in the other party's terminal. be. Hereinafter, the present invention will be described in detail using drawings showing embodiments.

The figure is a block diagram showing an embodiment of a terminal device constructed by applying the method of the present invention. 1 and 2 are terminal devices, which are connected via a general public communication network.

Now, when the terminal 1 performs a calling operation, the network control circuit 11 is activated. Since the network control circuit 11 activates the general public communication network, the general public communication network connects the terminals 1 and 2. Terminal 2
When the terminals 1 and 2 are connected, the network control circuit 21 is activated and the terminals 1 and 2 are able to communicate. The terminal number sending circuit 12 of the terminal 1 sends out the terminal number of the terminal 1, and the terminal number receiving circuit 22 of the terminal 2 receives this number. Next, the cipher sending circuit 13 of the terminal 1 extracts the cipher corresponding to the terminal 2 from the terminal number-based cipher storage circuit 14 and sends it to the terminal 2, so that the cipher is received by the cipher receiving circuit 23. On the other hand, the terminal number receiving circuit 22 sends the receiving terminal number (in this case, the number of terminal 1) to the terminal number-specific code storage circuit 24 and extracts the code number corresponding to the terminal 1. Thereafter, the code check circuit 25 compares the code received from the terminal 1 with the code extracted by the terminal number storage circuit 24, and if they match, normal communication is started.

When the communication ends, the code number generation circuit 26 is activated, generates a code using, for example, random numbers, and sends the code to the code storage circuit 24 for each terminal number.

Then, the terminal number-specific code storage circuit 24 updates the memory corresponding to the terminal 1 with the new code generated by the code number generation circuit 26. This code number generation circuit 26 is the code sending circuit 2.
7 to send the new cipher to terminal 1. Encryption receiving circuit 1
5 receives a new code and stores the code by terminal number circuit 14;
The memory corresponding to terminal 2 is updated to the new code. Thereafter, the connection between terminal 1 and terminal 2 is released.

In terminal 1, 16 is a terminal number receiving circuit, 1T is a code check circuit, 18 is a code number generation circuit, and in terminal 2, 2B is a terminal number sending circuit.
, 2 enable mutual transmission and reception of codes and terminal numbers.

As explained above, this invention has the effect of updating the encryption code for each communication call to the communication partner, thereby preventing leakage of the encryption code and maintaining the confidentiality of communication.

[Brief explanation of drawings]

The figure is a block diagram showing an embodiment of a terminal device configured to apply the present invention. 1.2... e terminal device, 11, 12 @ -- network control circuit, 12, 28... terminal number sending circuit, 13, 27
...Cipher sending circuit, 14, 24...Cipher storage circuit for each terminal number, 15.23...Cipher receiving circuit, 16
．． 22-...terminal number receiving circuit, 17,25・e...
Encryption check circuit, 18, 26... Encryption number generation circuit.

Claims (1)

[Claims] At the end of communication, a new code is generated on one side of the terminal station, and the code and the terminal station number with which the communication was made are memorized by both the local station and the other station, so that the terminal number and code of the other station match at the next communication. A communication terminal cryptographic control method that allows communication to occur when an error is detected.