JPS5826864B2 - wireless telephone system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides that communication signals to be exchanged between two selectively interconnected subscribers are transmitted subscriber-selectively encrypted and for this purpose are transmitted at each subscriber. The present invention relates to a multi-subscriber radiotelephone system in which an encryption device with a keyword generator is provided.

In such wireless telephone systems mainly used for mobile stations, for example, public mobile land radio (ObL) or non-public mobile land radio (N5b:t,), eavesdropping must be prevented in some way, i.e. Signals transmitted over the wireless channel are encrypted in an appropriate manner.

Stations that communicate with each other therefore almost always have one or more identical keys, which are installed in the equipment to change the settings, and after making the Communication transmission can be performed according to this key.

For operational or other specialized communication networks, it is known to store such keys in a decentralized manner, for example using electronic components or punched cards.

For subscribers of a public terrestrial radio communication network, for example, in the above-mentioned terrestrial radio communication, such a method is not possible due to the following points.

That is, the number of subscribers is large even within the relatively restricted radio area of the relay station, so that eavesdropping-proof transmission is not possible, or when setting the keys of the relay station individually, the keywords of all subscribers must be specified. The keywords that must be known and are active in all other relay stations throughout the network must also be known and therefore stored.

Since the exchanges must take place between thousands of subscribers, usually in a geographically dispersed network containing multiple relay stations, not only can key word messages be intercepted, but calls may also result from incorrect numbers. , which causes charge miscalculation.

It is an object of the invention to provide a solution to the above-mentioned problem as simple as possible and to eliminate the above-mentioned disadvantages.

The communication signals to be exchanged between two selectively interconnected subscribers are transmitted subscriber-selectively encrypted, and for this purpose an encryption device is provided in each subscriber with a keyword generator. According to the present invention, this problem is solved in the following manner in a wireless telephone system for a large number of subscribers.

That is, in the encryption device of the subscriber, a keyword string is determined in each case by a predetermined predetermined keyword for configuring the keyword generator, and a unique subscriber number is used for each subscriber for further transmission. Alternatively, unique encoded information may be stored, and a functional relationship known only to the upper exchange may exist between the subscriber number or unique encoded information and the predetermined keyword. ,
Furthermore, in the exchange, an encryption device corresponding to the encryption device of the subscriber is used, and the encryption device has a keyword generator capable of setting a keyword string according to a keyword and a computer, in which case the computer At the beginning of the formation of a connection between two subscribers, from the received subscriber number or the encoded information of this subscriber number, set the keyword generator of the encryption device provided for the connection. calculate individual keywords for each subscriber in order to Encrypted transmission between
This is done by converting keywords of incoming (arriving) information into keywords of outgoing (sending) information each time.

In this case, it is advantageous if the keywords are individually detected by a computer in the switching center before the start of the respective communication transmission and are erased again after the end of the call.

Furthermore, in order to ensure the security of the exchanged data, it is advantageous if the transmission of the subscriber number or code is repeated several times before the start of each call.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a subscriber Tn 1 whose call signal NF is converted into digital plain text KT (A/
D), and then in the mixer M controlled by the keyword generator SG to generate the ciphertext G by the keyword ST.
It is encrypted to become T.

This ciphertext is then transmitted by the transceiver device S/E.

On the receiving side, the reverse process takes place.

To establish the connection, first the encryption device SG+M is disconnected.

At some point, the subscriber Tn 1 is connected to the radio relay station, ie, the radio exchange ■, at its home location.

The radio relay station asks the subscriber for his or her subscriber number and, if necessary, whether there is a connection request.

The encryption device can be activated during the answering call to check whether the subscriber has already indicated the correct calling number.

Encryption itself is based on the following basic idea.

As usual the exchange must know all the keywords of all subscribers.

However, in large communication networks with a large number of exchanges, and each exchange has a very large number of subscribers, all these keywords must be memorized and therefore many technical and Since the cost is high, the following method is adopted in the present invention.

There exists a functional relationship between the subscriber number and the keyword corresponding to each subscriber individually, according to a certain mathematical function, but this function is known only to the keyword detector SC in the exchange. Not yet.

This keyword detector is informed of the subscription number, and on the basis of this number it detects the individual keyword of the calling subscriber within a very short time by means of an arithmetic unit and stores the keyword for the duration of the connection. S-8
It can be stored in p/V.

At this time, the exchange has already sent an encrypted response to the subscriber, and if the subscriber Tnl declares correctly, even after inputting the keyword generator SG that receives the keyword from the keyword memory 5-8p/F. , it should ensure that all communication transmissions between the subscriber and the exchange can still be understood.

If this is not the case, the subscriber will not receive a response.

This is because this subscriber does not understand the call of exchange V because of the different keywords, and thus no communication transmission takes place via an erroneous calling number and therefore an erroneous accounting.

It is impossible for a subscriber to attempt to understand all subsequent communication transmissions by manipulating the keyword generator or memory.

This is because they do not know the functional relationship between the subscriber number, ie the subscriber's selective calling code, and the encryption device keyword.

This relationship is known only to exchange ■ and is stored there in a special computer.

During a connection request from subscriber Tni to subscriber Tn3, for example, the exchange tries to find subscriber Tn3, if this subscriber primarily resides or is reachable in the communication network of this location, and The called subscriber also starts the same operation using the keyword attached to subscriber Tn3.

At the latest when a correct communication transmission takes place between subscribers Tn1 and Tn3, a transcoding of the keyword takes place in the encryption device SC of the switching center, i.e. the information received by both subscribers is decrypted and Connections are made at the level of plain sentences.

In this way secure communication transmission can be guaranteed.

This is because individual keywords are known only to the subscribers to which they belong.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a subscriber and switching center of the wireless telephone system according to the present invention, and FIG. 2 is a diagram for explaining the operation of the system of the present invention. Tn...Subscriber, ■...Exchange, A/
D...Converter, M...Mixer, SG・
...Keyword generator, S/E... Transmitter/receiver, S-8p/F, 5-8p/V...
・Keyword memory, SC...Keyword detector, KT...Plain text, GT...Ciphertext, ST...Keyword.

Claims (1)

Claims: 1. Communication signals to be exchanged between two selectively interconnected subscribers are transmitted in a subscriber-selectively encrypted manner and for this purpose a keyword generator is installed in each subscriber. In a wireless telephone system for a large number of subscribers, in which an encryption device is provided with determine the column,
Further, in order to carry out transmission, a unique subscriber number or unique encoded information is stored in each subscriber, and between the subscriber number or unique encoded information and the predetermined keyword, , a functional relationship known only to the upper level exchange exists, and furthermore, an encryption device corresponding to the encryption device of the subscriber is used in the exchange, and the encryption device can set a keyword string by a keyword. a keyword generator as well as a computer, the computer determining the connection from the received subscriber number or the encoded information of the subscriber number at the beginning of the formation of the connection between two subscribers. Calculate the individual keywords for each subscriber in order to configure the keyword generator of the encryption device provided for and then set the encryption for the individual keywords for each subscriber in this way. The encrypted transmission between the two subscribers connected through the switching center uses the equipment to transmit the keywords of the incoming information to the outgoing
A wireless telephone system characterized by exchanging information keywords each time. 2. Claim 1, in which the transmission of the subscriber number or code is repeated multiple times before the start of each call.
Wireless telephone system described in section.