JPH02295322A - Private communication system - Google Patents

Abstract

PURPOSE:To make it difficult to decipher a cipher only by wiretapping one channel by dividing one communication into two signals of 32kbps, mixing them with two divided signals of another channel, and outputting signals of 64kbps. CONSTITUTION:Voice signal sent from a telephone terminal(TR) 11 and 12 are converted into digital signals of 64Kbps by subscriber circuits(LC) 21 and 22 respectively, and sent out to a secret communication device(PCS) 40 through a digital exchange(TDSW) 30. The PCS 40 divides a digital signal of 64kbps of each channel into two digital signals of 32kbps, a digital signal of 32kbps of one channel is mixed with the digital signal of 32kbps of the other channel, and the resulting signal is sent out to a digital communication line through digital trunk interfaces(DIF) 51 and 52. Consequently, the cipher is not deciphered by wiretapping only one channel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to V: a secret communication system, and particularly relates to a secret communication system in a digital exchange.

[Conventional technology]

Traditionally, this type of secret communication method encrypted digital signals at the terminal or transmission path. [Problem to be solved by the invention] The conventional secret communication method described above encrypts the communication content, so a person who illegally obtains the encryption key can easily retrieve the original communication content. Since it can be restored, it has the disadvantage that it is not confidential communication. [Means for Solving the Problems] The secret communication system of the present invention is implemented in a digital exchange having a digital communication path for transmitting a 64 Kbps signal.
A means for dividing communication of one channel into two communications of a signal of 32 Kbps each, and one of the two divided communications.
The present invention is characterized by comprising means for combining two 32 Kbps signals with one 32 Kbps signal of a communication divided into two on another channel and outputting the resultant signal to the digital communication channel as a 64 Kbps signal. [Example] Next, the present invention will be described with reference to the drawings.

FIG. 1 is a system block diagram of a digital exchange showing an embodiment of the secret communication method of the present invention, and FIG. 2 is a circuit block diagram showing an example of the secret communication device in FIG. 1.

In Figure 1, voice signals emitted from telephone terminals (hereinafter referred to as T) 11 and 12 are respectively subscriber circuits (hereinafter referred to as LC) 2.
1.22 into a 64 Kbps digital signal, and sent to a secret communication device (hereinafter referred to as PCS) 40 via a digital switch (hereinafter referred to as TDSW) 2. PCS40
divides the 64 Kbps digital signal of communication on each channel into two 32 Kbps digital signals, combines the 32 Kbps digital signal of one channel with the 32 Kbps digital signal of another channel, and creates a digital trunk interface (hereinafter referred to as I IF). As shown in FIG. 2, the PCS 40 sent to the digital communication path via the signal switching unit (hereinafter referred to as SW) 41a, 4lb and the signal dividing unit (hereinafter referred to as DV)
) 42a, 42b, and a signal synthesis unit (hereinafter referred to as SN) 43a,
43b, and pattern recognition units (hereinafter referred to as DT) 44a, 44b
, a decoding section (hereinafter referred to as DC>45a, 45b), and a pattern generation section (hereinafter referred to as PG) 46.

Next, the operation of this embodiment will be explained.

When SW41a and SW4lb receive the unencrypted 64kbps digital signal from LC21 and LC22, respectively, they switch the signal from PG46 to recognize the delay time difference between the two divided communication channels prior to communication. DV42a, 4 sent to a42b
2b is 64Kbps from SW41a and 4lb respectively
After dividing the digital signal into two 32 Kbps digital signals, these are sent to the SNs 43a and 43b. For SN43a, one 32Kbps from DV42a
digital signal and one 32Kbp from DV42b
s digital signal is combined and sent to the IE) IF 51 side as a 64 Kbps digital signal. Also SN
43b is the other 32 from DV42a and 42b.
Kbps digital. The digital signals are combined and sent to the DIF 52 side as a 64 Kbps digital signal.

When the PCS 40 of the other station receives the above-mentioned combined digital signal from the digital communication channel via the DIFs 51 and 52, the SNs 43a and 43b each receive two 32K signals.
After dividing into bps digital signal, this is converted into DT44
a, 44b. DT44a and DT44b each perform pattern recognition and generate two digital signals (32Kb).
pS) is detected and sent to DCs 45a and 45b. DC45a,. 45b is DT44a respectively
, 44b, the signal is decoded into a 64 Kbps digital signal and sent to the LCs 21 and 22.

〔Effect of the invention〕

As explained above, the present invention can transmit one communication to two 32
By dividing the signal into Kbps signals, combining it with the two-divided signal of another channel and outputting it at 64Kbps,
Eavesdropping on just one channel has the effect of making decryption difficult. In addition, by transmitting two digital signals over two channels, encryption can be performed without increasing the number of invalid uses of the communication path.Furthermore, the secret communication device can be used as a common device for digital exchanges, and the exchange can decide whether to encrypt or not. This control has the effect of making it possible to effectively utilize the secret communication device.

[Brief explanation of the drawing]

FIG. 1 is a system block diagram of a digital exchange showing an embodiment of the secret communication method of the present invention, and FIG. 2 is a circuit block diagram showing an example of the secret communication device in FIG. 1. 11.12...Telephone terminal (T), 21.22...Subscriber circuit <LC) 30...Digital exchange (T)
DSW), 40...Secret communication device (PCS), 41
a, 4lb...Signal switching unit (SW), 42a, 4 2
b...Signal dividing unit (DV), 4 3 a. 4
3b-signal synthesis unit (SN), 44a, 44b-.
-Pattern recognition unit (DT), 4 5 a, 4 5
b--Decoding section (DC), 46... Pattern generation section (
PG), 51.52...Digital trunk interface (DIF).

Claims (1)

[Claims] In a digital exchange having a digital communication path that transmits a 64 Kbps signal, there is a means for dividing the communication of one channel into two communications of a 32 Kbps signal each, and a means for dividing one 32 Kbps signal of the divided communication into another channel. A secret communication system comprising means for combining one 32 Kbps signal of the communication divided into two and outputting the signal to the digital communication channel as a 64 Kbps signal.