JPH03169135A - Method and apparatus for maintaining cryptographic data - Google Patents

Abstract

PURPOSE:To prevent leakage of a cryptographic program by disconnecting a power line feeding power to a RAM when a 3rd party opens an enclosure covering a cryphtographic device and a central processing unit for a communication equipment illicitly to stop the power supply to the RAM and destroying the content of the RAM. CONSTITUTION:A relay 8 is operated via CPU 1 and a contact 81 of the relay 8 is closed by taking the normal procedure under maintenance that, e.g. a ten- key is operated to enter a password or the like. In such a case, the door of a cryptographic device is opened to activate a fault discriminator 71 and even when the contact of a switch 72 is opened, the RAM 2 is energized for its required operation through a power supply device 3, a diode 6 and the relay contact 81 of the relay 8, then secret data stored in the RAM 2 is not destroyed. However, if the door is opened illicitly, the fault discriminator 71 is operated, the contact of the switch 72 is opened, the power supply to the RAM 2 is stopped and the secret data stored in the RAM 2 is destroyed. Thus, the interception of the cryptographic program by the 3rd party is prevented.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method and device for preserving encrypted data in a communication device including an encryption device for maintaining communication secrecy in the field of facsimile and data communication. It is.

(Prior Art) In recent years, some communication devices in the field of facsimile and data communication have built-in secret data for encrypted communication.

When it is necessary to access such confidential data for maintenance and inspection purposes, the user must operate the numeric keypad to enter a password, etc., and go through formal procedures.

(Problem to be solved by the invention) However, when a third party illegally opens the encryption device and reads the contents of the memory that stores the secret data via the central processing unit, the encrypted data cannot be encrypted as secret data. There was a fear that the programs that were created would be leaked.

The problem to be solved by the present invention is to eliminate the above-mentioned problems, and at least solve the problem when an encryption device covering a central processing unit is illegally opened and an attempt is made to access secret data via the central processing unit. It is an object of the present invention to provide an encrypted data preservation method and a relatively inexpensive encrypted data preservation device for easily preserving encrypted data by automatically destroying the encrypted program.

(Means for Solving the Problems) In order to solve the above problems, an encrypted data preservation method according to the present invention uses an encryption device that performs encryption under program control of a central processing unit that cooperates with a RAM. A method for preserving encrypted data in a communication device including at least the central processing unit, which determines that an encryption device covering the central processing unit has been illegally opened, and disconnects a power line feeding power to the RAM;
This method is characterized in that the program in the RAM is destroyed by stopping power supply to the RAM.

The encrypted data security device is an encrypted data security device in a communication device that includes an encryption device that performs encryption under program control of a central processing unit that cooperates with the RAM, and is a power source that supplies power to the RAM. The apparatus includes an abnormality determination device that determines whether an encryption device that covers at least the central processing unit is abnormally opened, and a switch that connects the power supply device and the RAM and opens when the abnormality determination device determines that there is an abnormality. This is a characteristic feature.

(Function) In the encrypted data preservation method according to the present invention, it is determined that at least the encryption device covering the central processing unit is illegally opened without following a normal procedure. Based on this determination, the power supply line feeding the RAM is disconnected. By disconnecting the power line, the power supply to the RAM is stopped, which destroys the program in the RAM, and prevents the encrypted program as secret data from being passed on to a third party.

Further, as an apparatus for implementing the above method, an abnormality determination device determines whether an encryption device covering at least a central processing unit has been abnormally opened. Based on this determination, the switch is operated to open the circuit and the power supply line of the RAM is disconnected, thereby destroying the program stored in the RAM.

(Example) An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a CPU (central processing unit) that controls the entire device;
2 is a RAM (random access memory) that contains secret data for encryption, 3 is a power supply, 4 is a battery to back up the power of the RAM, 5 and 6 are diodes to prevent backflow, and 71 is an unauthorized An abnormality determining device 72 that determines when the door of the encryption device is opened is a switch whose contact is normally closed and operates in response to the abnormality determining device 71. For example, a displacement sensor that detects a mechanical change in the door is used as the abnormality determination device 71, and a contact that is driven to open by the sensor output is used as the switch 72. Or
As the abnormality determination device 71, the actuator of a microphone port switch is used in contact with the door, and as the switch 72, the contact mechanism of the microswitch is used. In this way, the abnormality determination device 71 and the switch 72 may be separate or integrated. 8 is C during maintenance
This is a relay that is turned on and off via the PUI, and 81 is a contact of the relay 8, which is normally open.

In normal times, the power supply unit 3 supplies the power required by the encrypted data security devices such as CPLI1, RAM2, and relay 8. In normal times, the RAM2 is connected to the power supply unit 3, the rediode 6, and the normally closed contact. Power necessary for the operation of the RAM 2 is supplied via the switch 72 of the abnormality determination device 71.

In addition, when the power is not supplied to the power supply unit 3 such as during a power outage, the RAM 2 uses the battery 4 for backing up the power supply to detect the diode 5 and the normally closed contact abnormality determination device 71.
Only the power necessary to maintain the contents stored in the RAM 2 is supplied via the switch 72.

If the door of the encryption device is opened illegally, the abnormality determination device 71 is activated and the switch 72 contacts open, causing the RAM 2
The secret data held in RAM2 is destroyed.

Also, during maintenance, by using regular procedures such as operating a numeric keypad and entering a PIN number, etc.
Relay 8 is activated via PLI1, and contact 8 of relay 8
1 closed.

In this case, even if the door of the encryption device is opened and the abnormality determination device 71 is activated, and the contact of the switch 72 is opened, the RAM 2 will be activated via the power supply device 3, the diode 6, and the contact 81 of the relay 8. Because it can supply the necessary power to the RA
The secret data held in M2 will not be destroyed.

After maintenance, the door of the encryption device is closed and the switch 72 of the abnormality determination device 71 is closed, and then the relay 8 is restored via CPtJ1 and the contact 81 of the relay 8 is opened.

In addition, in order to illegally leak confidential data in RAM, it is necessary to remove the CPU and install an in-circuit emulator, so the abnormality detection device is designed to detect abnormal opening of the casing that covers the CPU itself. You can also do this.

Further, the present invention is not limited to the above embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, when a third party illegally opens the casing that covers the encryption device and central processing unit of a communication device, power is supplied to the RAM. By disconnecting the power supply line, stopping power supply to the RAM, and destroying the contents of the RAM, leakage of the encrypted program can be prevented at a relatively low cost.

Therefore, according to the present invention, communication secrecy can be maintained, and reliability of the device can be enhanced by data security.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of an encrypted data security device according to the present invention. 1...CPU, 2...RAM, 3...Power supply device,
4... Battery, 5, 6... Diode, 71... Abnormality determination device, 72... Switch, 8... Relay, 8
1... Contact. Patent application Megumi Yamamoto, a human judge, Figure 1

Claims (2)

[Claims] (1) A method for preserving encrypted data in a communication device including an encryption device that performs encryption under program control of a central processing unit that cooperates with a RAM, the encryption device covering at least the central processing unit. The system determines that the RAM has been opened illegally, disconnects the power supply line that supplies power to the RAM, and stops power supply to the RAM.
An encrypted data preservation method characterized by destroying a program in M. (2) An encrypted data security device for a communication device that includes an encryption device that performs encryption under program control of a central processing unit that cooperates with the RAM, the power supply device that supplies power to the RAM, and at least the central processing unit. Encrypted data characterized by having an abnormality determination device that determines whether an encryption device that covers the device is abnormally open, and a switch that connects a power supply device and a RAM and is opened when the abnormality determination device determines that the error is open. Maintenance device.