JPS6115438A - Ciphering communication system - Google Patents

Abstract

PURPOSE:To simplify the operation of ciphering of an open key ciphering system by using a dial signal or a signal relating to the communication destination other than the dial signal to read a ciphering key of the communication destination from the stored open ciphering key, thereby ciphering information. CONSTITUTION:A signal representing a destination such as a dial pulse or a multi-frequency signal is transmitted from a dial signal generator 1 to a communication controller 2 and a line is set with the opposite party terminal device. A dial number detector 3 outputs an address signal corresponding to the opposite party. A key generating circuit 4 stores all open ciphering keys of subscriber terminals and outputs the open ciphering key of the opposite party to a ciphering device 6 based on an address from the detector 3. The ciphering device 6 ciphers the information from the information source 5 by using the given key and transmits the result to the opposite party terminal device through the controller 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a cryptographic communication system, and particularly to a cryptographic communication system in which communication information is encrypted and transmitted using a public key cryptosystem.

[Technical background of the invention and its problems]

Recently, financial institutions and the like have begun to recognize the importance of security issues, and the demand for encrypted communications is increasing. For example, in the United States, the encryption method is DES (Data Encryption).
It has been standardized by a standard called yption 3 standard. In this encryption method, the encryption key and decryption key are generally the same.

FIG. 3 shows the configuration of a communication system to which such an encryption method is applied, and is an example of encrypted communication between five terminals a to e. Each of the terminals a to e stores an encryption/decryption key Kij assigned to the other four terminals except for the own terminal. In this method, the encryption key and decryption key are common, so
If the key is known to a third party, it may be easily decrypted. Therefore, as the number of subscriber terminals increases, there is a drawback that key management becomes a heavy burden. Furthermore, even if each terminal manages its own keys reliably, there is always the fear that a third party could decrypt or eavesdrop on the key depending on how other terminals store the key. Under these circumstances, conventional methods have been used in which encryption keys and decryption keys are changed at short intervals (for example, every day), which is very complicated to operate.

In order to solve these problems, a cryptographic method called public key cryptography has recently attracted attention. This method uses the encryption key KEi (ia, b,
c, d, e) and the decryption key KO+ are made separate, and the encryption key is made public. That is, taking the case of sending information to terminal a as an example, the key KEa assigned to terminal a is used as the encryption key no matter which terminal sends the information. In this case, the key is set so that the decryption key cannot be found from the encryption key.

In this way, the number of encryption keys is equal to the number of subscriber terminals, and the only key to be stored is the decryption key of the terminal itself, making key management much easier. Therefore, it is believed that this public key cryptosystem will become extremely useful in the future as VLSIs develop further and terminal hardware becomes simpler.

However, this public key encryption method is different from the encryption method shown in Figure 3 in which the encryption key and decryption key are common, and even though the encryption key assigned to each terminal is constant, each time the other terminal is called, There is the complication of having to check the encryption key of the terminal and perform encryption.

(Objective of the Invention) An object of the present invention is to provide a cryptographic communication method that can simplify operations required when transmitting communication information after encrypting it using a public key cryptographic method.

[Summary of the invention]

The encrypted communication system of the present invention stores public encryption keys assigned to a plurality of communication terminals in advance, and uses a dial signal for calling a communication destination or a signal related to communication destinations other than this signal to make the stored public encryption keys The encryption key of the communication destination is selected from among the encryption keys, and a signal of that encryption key is automatically generated. Note that such a key generation means can be realized using, for example, a ROM.

〔Effect of the invention〕

'According to this invention, when a communication destination is called, an encryption key assigned to the communication partner is automatically generated and the communication information is encrypted. Therefore, when the calling operation and the key selection operation are performed separately, Operation is simplified compared to . Therefore, there is no inconvenience such as being unable to communicate due to the wrong selection of the encryption key applied to the communication destination terminal, and it is possible to communicate quickly and reliably.

[Embodiments of the invention]

FIG. 1 shows the configuration of a transmitting section of a cryptographic communication system according to an embodiment of the present invention. In this figure, a dial signal generator 1 is a circuit that generates a dial signal for calling a communication destination, and in the case of a normal dial type telephone, it generates a dial pulse, and in the case of a push button telephone, it generates a multifrequency signal. Occur. This dial signal is sent to the exchange network shown in FIG. 2 via the communication control device 2, and is also input to the dial number detection circuit 3. Note that the signal input to the dial number detection circuit 3 may be the dial signal itself, but it may also be a signal other than the dial signal as long as it indicates the destination of the communication. electrical signal (
(contact signal) may also be used. The dial signal dial number detection circuit 3 detects the communication destination (terminal) from the dial signal.

A signal indicating this is supplied to the key generation circuit 4. , key generation circuit 4
is the content of the public key list as shown in FIG. 4(b) in advance,
In other words, the public encryption key KEi assigned to the subscriber terminals other than the own terminal (of course, this may include the own terminal) is stored, for example, in a ROM.
Consisted of. When the key generation circuit 4 receives a signal indicating the communication destination from the dial number detection circuit 3, it reads out the public encryption key assigned to the communication destination terminal from the corresponding address in the ROM and outputs it.

This operation will be explained with reference to FIG. 2, which shows a communication network to which the present invention is applied. For example, consider a case where communication is performed from terminal a to terminal d. The dial number of terminal d is '2612'
Assuming that, the dial number detection circuit 3 is “”261
2° is detected, and a number specifying the address "°4" corresponding to this dial number is given to the key generation circuit 4. As a result, the key generation circuit 4 generates the public encryption key K assigned to the terminal d.
Generates an Ed signal, that is, a key code.

The key code from the key generation circuit 4 is supplied to the encoder 6.

The encoder 6 is supplied with information (digital data) to be communicated from the communication information source 5, encrypts this communication information using the key code from the key generation circuit 4, and sends it to the transmission circuit 7. The transmitting circuit 7 is, for example, a data modem, which converts the encrypted communication information from the encoder 6 into a predetermined signal form, and sends it to the switching network 8 through the communication control device 2 with a connection to the communication destination. .

As described above, according to the present invention, the public encryption key of the communication destination is automatically selected in conjunction with a dial operation for establishing a communication network, and communication information is encrypted and sent based on the public encryption key. Therefore, compared to a method in which the dialing operation and the encryption key search/selection operation ζ of the communication destination from the public key list are performed separately, the transmission operation is simplified, and there is an advantage that there is no possibility of entering the wrong encryption key.

According to the system of this invention, if the dialing operation is incorrect, the encryption key will be assigned to the wrong terminal, and a communication network will be established with the wrong terminal. This type of encrypted communication system sends an ident code after dialing and confirms the destination before starting communication, so there is actually no risk of information being inadvertently leaked to the wrong party. .

This invention is not limited to the above embodiments,
Various modifications can be made without departing from the gist of the invention.

[Brief explanation of the drawing]

'Figure 1 is a diagram for explaining the configuration of an encrypted communication system according to an embodiment of the present invention, Figure 2 is a schematic configuration diagram of a communication network to which the system of this invention is applied, and Figure 3 is a diagram for explaining the configuration of an encrypted communication system according to an embodiment of the present invention. Figures 4(a) and 4(b) are diagrams for explaining the configuration of a general cryptographic communication system that uses a common key for decryption and decryption, and show the configuration and public key list of a cryptographic communication system using public key cryptography It is a diagram. 1...Dial signal generator, 2...Communication control device,
3...Dial number detection circuit, 4...Key generation circuit,
5... Information signal source, 6 encoder, 7... Transmission circuit,
8... Exchange network. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] A dial signal generating means for generating a dial signal for calling a communication destination, and receiving a dial signal or a signal related to a communication destination other than this signal from the dial signal generation means, and communicating from public encryption keys of a plurality of communication destination terminals stored in advance. a key generation means for selecting a public encryption key and generating a signal of the public encryption key; and receiving a key signal from the key generation means;
A cryptographic communication system comprising means for encrypting and transmitting communication information based on a public cryptographic key given by the key signal.