JPS6161740B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secret communication device that prevents a third party from knowing an encryption code.

2. Description of the Related Art Conventionally, a secret communication device as shown in FIG. 1 has been used as a secret communication device for carrying out phone calls secretly. First, a digital audio signal encoded by an audio encoding device or the like (not shown) is inputted via an input line 2 to an addressing circuit 1 (for example, consisting of a shift register). On the other hand, the random access memory (RAM) 3, which is supplied with power from a normal power source via a line 4 or from a backup power source 5 for RAM, is supplied with a digital audio signal that is previously encoded and input via a line 6. A code (cipher code) is input and stored at an address (storage location) corresponding to the digital audio signal. Each secret code is read out by the address corresponding to each secret code from the addressing circuit 1. That is, the digital audio signal is encrypted into a secret code stored in the memory 3. The secret code read from the memory 3 is outputted via the secret code circuit 7 in synchronization with the input timing of the digital audio signal from the input line 2. On the receiving side, the received signal is subjected to operations opposite to those on the transmitting side to obtain the transmitted digital audio signal, and necessary communication between the transmitter and the receiver is performed without the knowledge of a third party.

However, the confidential code stored in the memory 3 can be relatively easily known to a third party if the code is placed in a state where the memory 3 can be accessed. Therefore, a third party who has obtained the secret code in this way can intercept the contents of the conversation being sent and received within the above-mentioned secret communication device. A secret communication device that has reached such a state effectively turns into a useless piece of equipment with no reputation, and the purpose of the secret communication cannot be achieved.

The present invention was devised to solve the inconvenience caused by the occurrence of the above-mentioned situation, and its purpose is to prevent a third party from accessing the memory that stores the encryption code for secret communication. To provide a secret communication device which automatically erases an encryption code in a memory so that the encryption code is not known to a third party.

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 2 shows an embodiment of the invention. In FIG. 2, reference numeral 10 denotes a conventional addressing circuit that outputs a read address of the RAM 12 determined according to input data (for example, a digital audio signal) sent via a line 11, and the address output from this circuit. Erasable memory, such as random access memory (RAM) 12, is accessed by. Memory 12 has RAM backup current 1
3, and the contents of the memory 12 are retained even if the power supply from the main power supply via the line 14 is interrupted. In other words, this RAM backup battery 13
is housed within the casing of the covert communication device, and when the device is removed from its designated installation location, the line 14
Even if the power supply via the power supply is stopped, the contents of the memory 12 are retained.

A secret code is previously stored in the memory 12 via a line 15 in the same way as in the conventional secret communication device, and the stored contents read from there are determined by the read address from the address designating circuit 10.
In other words, similarly to the circuit shown in FIG. 1, the digital audio signal input via the line 11 is read out from the memory 12 with its corresponding stored content, i.e., the secret code, and output via the secret code circuit 16, i.e., the encrypted code. coded.

In order to erase the stored contents of the memory 12 of such a confidential communication device, an erasing circuit 17 and a detection circuit 18 for operating the erasing circuit 17 are provided.

The erase circuit 17 is a power supply circuit including a micro switch 19 provided between the RAM 12 and the RAM backup battery 13.

The detection circuit 18 also includes a micro switch 19.
(See Fig. 3), this switch 19 has an actuator 22 that appears and retracts through a window 21 formed in the housing wall of a housing (for example, an in-vehicle radio) 20 that houses each of the above-mentioned components. , this actuator operates when the housing 20 is inserted into the fitting 23.

Next, the operation of the apparatus of the present invention having the above configuration will be explained.

When the confidential communication device of the present invention is under the control of the party handling it, the confidential code is maintained, so even if the output signal of the confidential communication circuit 16 is intercepted, the confidential code will remain confidential. An eavesdropper cannot tell what kind of audio signal is contained in the signal, and the original purpose of secret communication is achieved.

In addition, the RAM housed in the housing 20 described above
12 is placed in a state where a third party can access it,
That is, if the housing 20 is stolen, its RAM 12
When the housing 20 is pulled out from the mounting bracket 23 in order to read out the contents of the RAM 12, the actuator 22 of the switch 19 protrudes through the window 21, causing the micro switch 19 to open, thereby retaining the contents of the RAM 12. The power supply from the battery 13 to the RAM 12 is cut off (prior to this, the power supply from the main power source is cut off). Therefore, the contents of RAM 12 will be partially or completely erased,
Even if the lid of the removed casing 20 is opened and the contents of the RAM 12 are read, the read contents are not secret codes. Therefore, the secret code is not known to a third party, and the function of the secret communication device is maintained.

In the above embodiment, the transmitting side has been described, but the same applies to the receiving side. Furthermore, instead of operating the erasing circuit 17 when the housing 20 is pulled out from the mounting bracket 23,
The erasing circuit 17 may be operated when the lid of 0 is opened. Furthermore, although the explanation has been given using an audio signal as an example, the present invention can also be applied when the input data is image data, and the memory 12 stores an encryption code for the image data.

As is clear from the above description, according to the present invention, when a party or a third party engaged in operating a secret communication device attempts to access a memory storing an encryption code, the casing housing the encryption code is placed at a predetermined installation position. When an attempt is made to remove or open the lid, the encryption code in the memory is automatically erased and the code is preserved. Therefore, the confidentiality of the secret communication device is maintained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional device, FIG. 2 is a diagram showing the device of the present invention, and FIG. 3 is a diagram showing a casing to which a microswitch is attached and a state in which the casing is inserted into a mounting bracket. In the figure, 12 is an erasable memory, 17 is an erasing circuit, and 18 is a detection circuit.

Claims (1)

[Claims] 1. In a secret communication device in which an erasable memory that outputs a code that converts input data into encrypted data or decrypted data is housed in at least a housing, an operation for the purpose of stealing the memory code in the housing is prohibited from occurring in the housing. A detection circuit for detecting an effect on the body and an erasing circuit for the memory are provided, and the erasing circuit is operated in response to the output of the detection circuit to erase the code in the memory. A secret communication device.