JPS6058737A - Ciphering device - Google Patents

Abstract

PURPOSE:To erase automatically confidential information stored in a memory of a main body section against an external incorrect access by providing a means detecting it when a part of an outer case is opened to output an internal access signal and a means outputting an incorrect access signal when the output of the internal access signal is detected. CONSTITUTION:An internal access detection circuit 22 is a circuit generating an internal access signal when a door is opened for access to the inside, a columnar projection 14 is detached, a spring 15 is released and contacts are opened. Further, a deciding circuit 23 is a circuit generating an incorrect access signal by discriminating it as the incorrect access if the internal access signal is generated regardless that no access start signal is given, and an erase signal generating circuit 12 is a circuit generating a signal in receiving the incorrect access signal to erase confidential information stored in a memory 25. Through the constitution above, upon the arrival of the incorrect access, the confidential information stored in the memory is erased and the security of information is maintained.

Description

[Detailed description of the invention] The present invention relates to a cryptographic device, and in particular, 1 It is related to the device.

Generally, electronic devices, especially so-called desktop devices placed on desks in offices, etc., have an external casing or chassis called an enclosure. It is wrapped so that it cannot be touched directly from the outside. In such ordinary general electronic devices, screws and the like are exposed to the outside for ease of assembly and maintenance.1 The main body inside the chassis can be easily exposed using a tool such as a screwdriver. Is possible.

However, in the case of a cryptographic device, information such as an electronic key that is not known to a third party is usually stored inside the device.
While maintaining ease of device assembly and maintenance, it is necessary to erase information stored inside the cryptographic device against unauthorized access. This point is also mentioned in the US Federal Standard 1027 regarding cryptographic devices. For normal access, a lid or door with a lock is usually attached to the top or front of the enclosure, and the interior is accessed by unlocking it using a key or electromagnetically.

Ideally, the structure of a cryptographic device would be such that no screws or the like appear on the outside to prevent unauthorized intrusion from the outside. It can be made without screws or without putting screws on the outside.

Difficult to assemble and maintain. In addition, since there is a limit to the mechanical strength of lids and doors, or their attachments, by mechanically destroying them, it is possible to completely prevent unauthorized access to the interior, even if the lock is unlocked properly. It is difficult to do so.

Therefore, an object of the present invention is to create a cryptographic system that can automatically erase confidential information stored in the memory of the main unit against unauthorized access from the outside, even if the structure is not perfect. It is intended to obtain equipment.

According to the present invention, there is provided a main body provided with an electronic circuit including a memory for storing secret information; an external casing that covers at least a main part of the main body; In a cryptographic device having an access means for accessing the inside of the device and an access operation initiation means for allowing operation of the access means for accessing the inside of the device, when the access operation initiation means operates, this is detected and the access is started. means for outputting a signal; means for detecting when a portion of the external casing is opened and outputting an internal access signal; and determining that the access start signal is not output and the internal access signal is output. There is obtained a cryptographic device characterized by comprising means for outputting an unauthorized access signal when detecting the unauthorized access signal, and means for erasing secret information stored in the memory using the unauthorized access signal.

Next, a detailed explanation will be given using the drawings.

FIG. 1 is a sectional view showing the configuration of an encryption device which is an embodiment of the present invention. Reference numeral 1 denotes an enclosure, and a door 3 equipped with a lock 2 for starting regular access is attached to the front surface of the enclosure so that it can be opened and closed by a hinge part 4, so that the inside can be accessed in the open state. Reference numeral 5 denotes a main body, on which electronic circuits and other parts 7 are mounted on four plates 6, and a rear plate 8 (which serves as part of the enclosure) facing the outside (left side). ) and a front plate 9 facing to the right in the figure is attached to the lowest plate 6'. The main body part 5 is screwed and fixed to the enclosure from the front side by means of a holder 10.9. The screws cannot be removed unless the door 3 is opened. By removing the screws, the main body 5 can be removed from the left opening of the enclosure 1 to the outside.

Both 11 and 12 are microswitches, and the black dots indicate the terminals that are individually connected to the two internal contacts (5). Or by opening it.

Among them, the first microswitch 11 is for detecting that there is an operation to start normal access to the lock 2, that is, an unlocking operation. For this reason, in addition to its normal functions, the lock 2 is equipped with a bar 12 with a rectangular cross section, indicated by a dotted line in the figure, that moves perpendicular to the plane of the paper. By pressing the spring plate of the microswitch 11, the contacts are switched from disconnected to connected. The purpose of the detection function will be explained later.

A second microswitch 12 provided on the front surface of the bottom of the main body 5 is for detecting opening/closing of the door 3 for accessing the inside. In the case of a device having the structure shown in FIG. 1, for example, as mentioned above, the main part of the door 3 is burnt off, or the hinge part 4 is burnt off to remove the door 3, and the main body part 5, especially the terminals on the front surface thereof, are removed. and access to the circuit adjustment structure.
Secret information can be stolen from the secret information input terminal.

(6) In order to prevent this, a columnar projection 14 is fixed on the door 3 at a position facing the microswitch I2, and when the door is closed, the columnar projection 14 presses the spring plate 15 of the microswitch 12 and the two For example, if the internal contacts are connected, and if the door is open, the spring plate 15 is opened and the two contacts are disconnected, and the change in connection or disconnection between these contacts is detected. If so, the door 3 can be opened, and therefore the secret information in the memory can be erased.

However, if the secret information in the memory is erased only by detecting the opening/closing of this door, it will become impossible to adjust the front surface of the main body 5 and write the secret information.
The above problem is solved with the help of the operation of the microswitch 12.

FIG. 2 is a diagram showing an example of the configuration of a part of a mechanism and an electric circuit for erasing secret information in memory in the event of unauthorized access from the above-mentioned connection/disconnection conversion of the two microswitches. In FIG. 2, the same components as in FIG. 1 are given the same reference numerals. It should be noted that the two microswitches 11 and 12 are schematically shown, and the relative position and orientation between the switch 11 and the lock 2 are different from those in FIG. 1 to make the operation easier to understand.

This figure 2 shows a state in which all the components are in their normal positions, with the first and second microswitches 11
and 12, the spring plate 15 or 15' is pressed and the contact points are in contact. And access start detection circuit 21
is a circuit that emits an access start signal a when the lock is unlocked to start accessing the interior, the rod 13 moves upwards in the figure, the leaf spring 15' is released, and the contacts are disconnected.

The internal access detection circuit 22 is a circuit that emits an internal access signal when the columnar projection 14 is separated and the spring plate 15 is opened when the door is opened to access the interior, and the contacts are disconnected. Further, the determination circuit 23 receives the access start signal a.
When it detects that the internal access signal S has been issued even though the internal access signal S has not been issued, it is assumed that there has been an unauthorized access, and the erasure signal generation circuit 24 issues the unauthorized access signal C. When received, this circuit issues a signal and erases the secret information stored in the memory 25.

With the above configuration, if there is unauthorized access, the confidential information stored in the memory will be erased, making it possible to maintain confidentiality; however, if there is legitimate access, the main unit will be deleted without erasing the confidential information. can be removed from the enclosure.

In the above embodiment, the key 2 mechanically operated with a key and the microswitch 13 are used as a means for starting the access operation, but the invention is not limited to this, and a device that electromagnetically controls one lock is used. It may be. Moreover, instead of the door 3 with the columnar projection 14 for accessing the inside, a lid screwed from the outside may be used. However, in either case, a switch portion that causes electrical disconnection is attached to the main body portion 5.

As explained above, according to the present invention, if there is unauthorized access, the confidential information stored in the memory will be deleted, making it possible to maintain confidentiality. Since the information (9) is not deleted, there is no need to take the extra effort to re-memorize it.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of a cryptographic device according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of a part of the mechanism and circuit configuration of the device shown in FIG. Explanation of symbols: 1 is the external casing (enclosure). 2 is the lock, 3 is the door, 5 is the main body, 6 and 6' are plates, 7 is parts such as electronic circuits, 8 is the rear panel, and 9 is the front panel. 10 is a holder, and 11 and 12 are microswitches. 13 is a rectangular bar, 14 is a columnar projection, and 15 is a spring plate. 16 is a metal support, and 21 is an access start detection circuit. 22 is an internal access detection circuit, and 23 is a determination circuit. 24 is an erase signal generating circuit, and 25 is a memory. Agent (7127) Patent attorney Yosuke Goto (10)

Claims (1)

[Claims] 1. A main body provided with an electronic circuit including a memory for storing secret information, an external casing that covers at least the main part of the main body, and a device for accessing the inside by opening a part of the external casing from the outside. In a cryptographic device having an access means to the inside and an access operation start means for allowing the operation of the access means to the inside of the device, means for detecting when the access operation start means operates and outputting an access start signal. and a means for detecting when a part of the external casing is opened and outputting an internal access signal, and detecting that the internal access signal is output while the access start signal is not output, prevents unauthorized access. An encryption device comprising: means for outputting a signal; and means for erasing secret information stored in the memory in response to the unauthorized access signal.