JPH0151106B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention controls a data communication encryption device installed between a data line terminating device (DCE) and a terminal device (DTE) provided at each end of a data line. Regarding the method.

Background of the Technology In order to protect data on communication lines, an encryption device is inserted between data line terminating equipment (hereinafter referred to as DCE) such as a modem or home line terminating equipment and terminal equipment (hereinafter referred to as DTE). , Techniques for encrypting and transmitting data are well known.

The most well-known cryptosystems of this type are conventional cryptosystems that use the DES algorithm and public key cryptosystems that use one-way functions. However, conventional cryptosystems have problems with key management, and public-key cryptosystems have problems in that high-speed encryption processing is difficult. For this reason, a mixed method of using a conventional cryptosystem for encryption and a public key cryptosystem for key management has recently been attracting attention.

Prior Art and Problems According to the mixed method of conventional cryptography and public key cryptography as described above, key distribution is performed by public key cryptography, and keys for the conventional cryptography are created thereby. . The problem with this mixed method is how to determine the key distribution time. That is, in DTE, normally, the waiting time from transmitting a data terminal equipment ready (hereinafter referred to as ER) signal ON until receiving a data set ready (hereinafter referred to as DR) signal ON, or a transmission request (hereinafter referred to as RS) ) There is a fixed waiting time from when the signal is sent to when the clear to send (hereinafter referred to as CS) signal is received, and if the key distribution is not completed within this waiting time, the DR signal is turned on or the CS signal is sent. If it does not receive an on signal, the DTE assumes that the DCE is faulty and disconnects the line. This is because the DTE side cannot see the encryption device, only the DEC.

OBJECT OF THE INVENTION Therefore, the present invention solves the above-mentioned conventional problems, and an object of the present invention is to enable normal encrypted communication even if key distribution communication between encryption devices is not completed within a predetermined time. The object of the present invention is to provide a cryptographic device control method that can perform the following functions.

Structure of the Invention A feature of the present invention that achieves the above-mentioned object is that, in a signal control method of an encryption device provided between a data circuit terminating device (DCE) and a terminal device (DTE), the present invention is characterized in that a signal control system for an encryption device provided between a data circuit terminating equipment (DCE) and a terminal equipment (DTE), When a data terminal equipment ready (ER) signal or a transmission request (RS) signal is sent from the terminal equipment (DTE) side, a timer with a predetermined length of time is started, and the timer counts the predetermined time during the key distribution communication. If the clock is finished, send a data set ready (DR) signal or clear to send (CS) signal to the terminal equipment (DTE) at the end of the time measurement.
The reason is that it was sent to the side.

Examples of the invention The present invention will be explained in detail below using the drawings.

FIG. 1 schematically represents the entire communication system in one embodiment of the present invention. DTE10,1
2 are connected to DCEs 18 and 20, which are a modem and a home line termination device, via encryption devices 14 and 16, respectively. The DCEs 18 and 20 are connected by a communication line 22.

FIG. 2 shows an example of the configuration of the cryptographic device 14 shown in FIG. However, in this case, it is represented as an encryption device on the sending side. In FIG. 2, 24 is a cryptographic calculator that converts transmission data (hereinafter referred to as SD) from plaintext to ciphertext, and 26 is a DTE1
0-related control signal control unit, 28 is DCE18
This is a control unit for controlling control signals related to. Further, 30 is a control section for controlling communication between the present encryption device 14 and the receiving side encryption device 16, 32 is a timer circuit, and 34 is a switch means for switching transmission data. Timer circuit 32 is DTE10
When the ER signal is turned on, it starts a timing operation (timer start), and when a predetermined time period ends (timeout), it sends a DR signal on to the DTE side.

FIG. 3 is a time flow chart in the configuration example of FIG. 2, and the operation of this embodiment will be explained below using this diagram.

First, the cryptographic device 14 sends and receives control signals such as ER signals, DR signals, RS signals, and CS signals to and from the DCE 18, connects the line with the cryptographic device 16 on the receiving side, and then starts key distribution. . In this case, the switch means 34 is switched to the control section 28 side, and the inter-encryption device communication control section 30 performs communication control and generates a key. When the ER signal ON is sent from the DTE 10 side, the timer circuit 32 starts timing operation. When the timer circuit 32 finishes counting the predetermined time during key distribution, the timer circuit 32 transmits DTE.
Since the DR signal ON is sent to the 10 side and the switch means 34 is switched to the cryptographic calculator 34 side, key distribution is forcibly stopped. then
When receiving the RS signal ON from the DTE 10 side, the encryption device 14 transmits the RS signal ON to the DCE 18, and the DCE 20 on the receiving side turns on the carrier detection (hereinafter referred to as CD) signal due to the carrier sent by the DEC 18. do. Thereafter, the cryptographic device 16 on the receiving side learns that key distribution has been forcibly stopped by an initialization vector (hereinafter referred to as IV) signal sent from the sending side, and starts encryption using the previously used key. . Therefore, from now on, DTE
The SD sent from 10 is encrypted using the previous key and sent to the other party, and the encryption device on the other party also decrypts it using the old key. Note that the cryptographic device 16 on the receiving side can learn of forced suspension of key distribution by analyzing the distribution procedure in addition to the IV signal, or can know by some other means.

If the key distribution is completed before the timer circuit 32 finishes counting, the DR signal ON is sent from the three communication control units to the DTE 10 at the time of completion, and the switching means 34 is also switched at the same time.
Thereafter, the same operations as in the above case are performed. However, in this case, encryption is performed using a new key.

FIG. 4 shows another example of the configuration of the cryptographic device 14 shown in FIG. In the configuration example shown in Figure 4, DTE10
A switch means 36 is provided between the SD signal terminal of the cryptographic calculator 24 and the cryptographic calculator 24. The switch means 36 and the switch means 34 are controlled only from the inter-cipher communication control section 30 side, and not from the timer circuit 32 side. The rest of the configuration of this configuration example is exactly the same as that of FIG. 3.

FIG. 5 is a time flow chart in the configuration example of FIG. 4, and the operation of this embodiment will be explained below using this diagram.

The operation until the ER signal ON is sent from the DTE 10 during key distribution and the timer circuit 32 starts timing is exactly the same as in the case of FIG. 2.
However, in this embodiment, even if the timer circuit 32 finishes counting, the key distribution is not forcibly stopped. In other words, when the timer circuit 32 times out, the DR signal ON is sent to the DTE 10 from the timer circuit 32. However, the switch means 34 remains connected to the control section 28 side, and the switch means 36 also remains open. Therefore, the SD from the DTE10 side until the key distribution is completed.
All signals are ignored. When the key distribution is completed, the switch means 34 is switched to the cryptographic calculator 24 side by a signal from the communication control section 30, and the switch means 36 is closed, so that from now on, encryption is performed using the newly created key. The other party also performs decoding.

The operation when the key distribution is finished before the timer circuit 32 finishes counting time is clear from the above description, and will therefore be omitted.

Note that although the above-mentioned embodiment relates to the ER signal and the DR signal, the present invention also applies to the same thing.
It is clear that the same procedure may be applied to the RS signal and the CS signal.

Effects of the Invention As explained in detail above, according to the present invention, a timer is started when the ER signal or RS signal is turned on during key distribution, and when the timer finishes counting a predetermined time, the DR signal on or
Since the CS signal ON is sent to the DT side,
Even if key distribution communication between cryptographic devices does not end within a predetermined time due to terminal characteristics or the like, it is possible to perform cryptographic communication normally.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically representing an entire embodiment of the present invention, FIG. 2 is a block diagram of an example of the configuration of an encryption device, and FIG. 3 is a time flow chart of signals in the device of FIG. FIG. 4 is a block diagram of another example of the configuration of the cryptographic device, and FIG. 5 is a time flow chart of signals in the device of FIG. 10,12...DTE, 14,16...Encryption device, 18,20...DCE, 22...Communication line,
24... Encryption calculator, 26... DTE control signal controller, 28... DCE control signal controller, 30...
Communication control unit between cryptographic devices, 32...timer circuit, 3
4, 36...Switch means.

Claims (1)

[Claims] 1. In a signal control system for an encryption device provided between a data line termination device and a terminal device, a data terminal device ready signal or a transmission request signal is sent from the terminal device side during key distribution communication between the encryption devices. is sent, a timer of a predetermined length of time is started, and if the timer finishes counting the predetermined time during the key distribution communication, a data set ready signal or a send ready signal is sent to the terminal device side at the time when the timing ends. A control method for a cryptographic device, characterized in that: 2. The control method according to claim 1, wherein the key distribution communication is stopped when the timer ends. 3. The control method according to claim 2, wherein if a new key has not been created, the previously created key is used. 4. The control method according to claim 1, wherein the key distribution communication is continued even after the timer finishes counting, and transmitted data is ignored during the key distribution communication. 5. If the key distribution communication ends before the timer ends, a data set ready signal or a send ready signal is sent to the terminal device at the time the communication ends. Control method described in section.