Method for making an enciphered radio communication

Technical field

The invention relates to a method for performing an encrypted radio traffic between transceiver stations, particularly mobile transceiver stations, in which use all together a radio network forming transceiver stations the same day key and operate synchronously.

Underlying the art

For operation of radio networks, especially in radio networks for tactical use, it is important that on the one hand the information to be communicated to the only available to those authorized to do so and is furthermore also taken to ensure that no unauthorized transceiver station through targeted radio measures the radio traffic can interfere with or cause the transmission of misinformation confusion.

To achieve a high confidentiality of the information to be transmitted, it is, for example, the document DE-OS shows 21 6O 132, common to transfer the information in the digital domain and to encrypt the digital information in an appropriate way with a key signal sequence. In order to enable an orderly radio movement thereof, the individual transmitting-receiving stations need to use both the same days key and operate synchronously in time. Usually, as stating the mentioned reference, the key signal sequence derived in the transmission of information from a sending station to a receiving station in each of the time, a code number and the date key and transmit a time-dependent synchronization and identification information at the beginning of the encrypted transmission.

the allowable mutual time offset of a compound moving together desiring stations in sufficiently small limits, then sufficient instead of synchronizing a time signal information, for example in the form of a Barker code to produce the desired synchronism, which is prerequisite for a receiving station that their the of sending station sent identification information can take. The expenditure on equipment is very large in this case, because in this case the accuracy of the station clocks extremely high demands are made. In addition, the required, extremely precise initial synchronization of the station clocks of all transceiver stations of a wireless network under normal environmental conditions can only be achieved with considerable expenditure of time.

Is this high technical complexity undesirable and should manage the transceiver stations in terms of their station watches with inexpensive quartz crystals, then have to be overcome when establishing a connection sometimes considerable time differences between a compound desiring each other stations. To this end, then serves an extensive synchronization information that transmits the necessary time to the receiving station by the transmitting station. This synchronization information is transmitted unencrypted and is allgemeimen with regard to the transfer to demanding safety relatively long, resulting in unacceptably long build times, especially at low bit rates radio. Is also not made of a time-controlled real encryption use, the scope of the synchronizing information or by the special start information for the key generator of the receiving station is further increased.

Disclosure of the Invention

The invention is based on the object for a method for performing an encrypted radio traffic of the kind described in the introduction using a real time-controlled encryption provide another solution that allows a fast connection with high security against abusive intrusion of an interferer between two connect desiring transceiver stations taking into account considerable, in this case to be corrected time differences between the clocks of these two station transceiver stations.

This object is achieved according to the invention by the features specified in patent claim 1.

In real time controlled encryption is to ensure a high level of classified information to be transmitted, the amended inter alia by the station clock time certain time key in relatively short intervals. The invention is based on the insight that for the connection setup, while respecting the necessary security against abusive intrusion or the protection of this is done without information to be transmitted at a much lower key diversity than is required in the actual useful signal. This allows a two-stage process in which the validity of the time key in the construction phase of the connection is many times longer than in the Nutzinformationsübertragungsphase is. The longer validity period of time key during the construction phase of the compound now has the great advantage that the information transmitted from the calling station information on the called station can be detected in a much larger time tolerance range than in a much shorter period of validity of the time key, as they during the actual Nutzinformationsübertragung must be used, would be the case.

Expedient embodiments of the method according to the invention are given in the further claims 2 to. 6

Brief Description of Drawing

In the drawing, the detailed explanation of the invention serving figures mean<dl id="dl0001"><dt>Fig. 1</dt><dd>a the transmission function closer explanatory partial block diagram of a transmission-Empfangsstsation with real time controlled encryption,</dd><dt>FIG. 2</dt><dd>the function of the receiving side closer explanatory partial block diagram of a transmitter-receiver station with real time controlled encryption,</dd><dt>Fig. 3</dt><dd>Time diagrams for a more detailed explanation of the operation of establishing a connection between transmitter-receiver stations according to the figures 1 and 2. FIG.</dd></dl>

BEST MODE FOR CARRYING OUT THE INVENTION

The partial block diagram of a transmitter-receiver station of FIG. 1 has a Schlüsselsigsnalerzeuger SSG, which operates with a characteristic value transmitter KWG together. Furthermore, the partial block diagram of FIG. 1 a transmitter S on the input side is connected via a changeover switch U1 with an optional output of the key signal generator SSG and a further switch U2 across the output of the mixer MD2, the input side supplied the unencrypted digital useful signal SIG becomes. The key signal generator SSG, the characteristic value transmitter KWG, and the switch U1 and U2 are commonly controlled by the sequence controller AST in their functioning.

The key signal generator SSG has a basic key transmitter SG, in which the or days keys are stored. At the basic key donors SG the days key register R1 connects, in the days of the keys used in each case is taken and can be retrieved if necessary. Furthermore, the key signal generator SSG key computer SR on the input side via the mixer MD1, which may be for example, a modulo-2-adder as the mixer MD2, a mixed signal is fed from the daily key and the signal supplied from the characteristic value transmitter KWG. For this, the actual ZS time key signal representative of the key computer SR generates the key signal sequence that is supplied to the downstream of it keystream memory SF.

The characteristic value transmitter KWG has a central clock TK, on ​​the one hand the clock T for the various modules supplies and moreover has a station clock whose accuracy is determined by the oscillation of the quartz generator G. The central clock TK is connected for setting the station clock with a controlled by the sequence controller AST station clock adjusting EV. The respective time is delivered in digital form by the central clock TK respectively at their downstream characteristic memory R2. The characteristic value memory R2 is also connected to an adjustable code number encoder NE whose set code number is also stored in the parameter memory R2. The light emitted from the characteristic value transmitter KWG signal from the parameter memory R2 to mixer MD1 thus consists of the station clock time and a code number each. The code number here may be the subscriber number of a transmitting-receiving station or a hunt group number for multiple transceiver stations with which a connection is to be made.

In idle mode, all belonging to a radio network transceiver stations are ready to receive and all point to the same day key. The key sequence generated in the key signal generator SSG in the rhythm of the change period of time key ZS, which is respectively stored in the key sequence storage SF, takes place in a long time mode (Long Key Li) is provided here for a connection. The characteristic value memory R2 of characteristic encoder KWG receives it from the code number encoder NE own subscriber number or a hunt group number.

Now Wants a transceiver station a connection with a subscriber station or a compound having a plurality of subscriber stations via a collective call, then the code number encoder NE is first adjusted to the number of the subscriber or on hunting calls for multiple transceiver stations and the rhythm of the exchange period time key ZS in long time mode generates a corresponding time code at the output of the mixer MD1. This time key ZS, since it already contains the number of the participants, are directly emitted as an encrypted call address. The time key ZS is thereby supplied from the output of the mixer MD1 via the switch U1 in the switching position shown in broken line the transmitter S. Because of the long validity of the long-term key, the thus formed encrypted call address can still be detected on the called station in a relatively large time-tolerance range. Once the called station recognized the call address and he has become recognized depending their station clock in synchronism with the station clock of the calling station, then switch to the much shorter exchange period of time key ZS in the short time mode (short-time key Kiv) can be switched and using this temporary key, the actual useful signal transmission be performed.

Receiving and evaluating the encrypted call address will be explained in detail with reference to the part of the block diagram of FIG. 2. In partial block diagram of FIG. 2, the key signal generator SSG and the characteristic value transmitter KWG are only shown as simple blocks. The incoming encrypted call address is the recipient e supplied via the antenna AN and the duplexer W, which in turn is also controlled by the sequence control AST. The sequence control AST causes both the long-time key generated on this transmission-reception station and the received encrypted call address are supplied to the paging receiver RE. The call receiver RE comprises two key storing MR1 and MR2 in the form of registers and a related key storing comparator V, of which the key memory MR1, the local time key ZS in the long time mode and into the key memory MR2 which also a time key ZS in Time Exposure Performing received encrypted call address are stored. Depending on the Vergleicherergebnisses the local time key is as long as one bit displaced in the key memory MR1, to the comparator V of the flow control AST reports the temporal coincidence of MR1 and MR2 stored in the two key Save time keys on the sequencer AST. In response to this message, the scheduler AST the station clock the characteristic encoder KWG on the station clock adjusting EV so after that exists between the calling transceiver station and the called transceiver station synchronism. Can then be transmitted via a feedback information of gerufenenen transceiver station to the calling transceiver station information, such as a start information of the dependent then the scheduler AST switching can be carried out by the long-term key to the short-term key.

In the embodiment of FIG. 2, this can be done by this information generated by the characteristic value transmitter KWG and the transmitter S can be made to radiate from the antenna A via duplexer by switching the switch U2 in the dashed shift position from the characteristic value transmitter KWG. In the illustrated switch position of the change-over switch U2 of Figures 1 and 2, the upcoming digital useful signal SIG to be fed as an encrypted digital signal SIG 'the transmitter S via the mixer MD2 time.

To carry out a connection establishment of the encrypted call address Performing time key can be provided with a time information ZS with each repetition made during its validity time. When part of the block diagram according Fi. 1, this can be done in that short time, the switches are U1 and U2 brought into the broken switch position following the issue of a time key ZS to the input of the transmitter S, in which then the encrypted call address time information can be added by the central clock TK , If the exchange period for the short-term key is an integer multiple of the change period of the long-term key and is made of the time information and the encrypted call address page information i, A limited in time to a changing period of the short-term key, then the time information is expediently consist in which short-term key, the timing of the respective call information corresponds in the sequence of short-time keys within an alternating period of the long-term key.

This time information may, as in the partial block diagram of FIG. 2 is indicated, the receiver E are fed directly via the time information receiver ZE of flow control AST and also the sequence of the time information in the repetitive call information for deriving the start information are used, by using switching to be transferred to the short-term key from the long-term key to the transmission of the actual payload. If in the context of the transfer of the useful information to also time information to be transmitted from and these can be taken also on the time information receiver ZE at the recipient's e second output and fed through the time information receiver ZE of flow control AST.

That the recipient's e second output incoming encrypted digital useful signal SIG 'is in the mixer MD3, for example, may also be a modulo-2 adder, decrypted and the decrypted digital useful signal SIG at its output for its further processing provided.

As the partial block diagram of FIG. 2 can be further seen that the key sequence emitting output of the key signal generator SSG through the switch U3 selectively to the mixer MD2 and MD3 to the mixer is connectable. Depending on whether the relevant transmitting-receiving station is operating in the transmit or receive mode, the changeover switch U3 is converted into the broken or in the extended operating position of the flow control AST. If a real-duplex operation to be performed, and the switch U3 can enfallen and the mixer MD2 and MD3 are connected directly to the key sequence output supplying the key signal generator SSG.

With reference to the time charts shown in Fig. 3, the operation of a connection setup will now be explained in more detail in which it is assumed that the time difference between the station clock of the calling transmitting-receiving station and the station clock of the called transmitting-receiving station is greater than a change period of time key in long mode.

The top timing diagram shows E1L over time the long-term key generated in the rhythm of a change period of the called transceiver station LO, L1, L2 and L3. The exchange period of the long-term key extends over eight alternating periods of long-term key. The long-term keys LO, L1, L2 and L3 associated short-term key KO1 ... KO8, K1O ... K18, K28 ... K2O and K3O ... K38 are shown in the timing diagram E1K. In either by the period of a short-time key portion shown within the validity period of a long-term key, LO, L1, L2 and L3 an encrypted call address A is transmitted from the transmission side, the respective timing information 1, 2, 3, 4, 5, 6, 7 and 8 assigned. This time information are respectively at the timing of the just transmitted encrypted call address based on the exchange periods of short-term key within the validity period of a long-term key.

In the timing chart S1L which indicates the sequence of successive alternating periods of long-term keys L1, L2, L3, L4 and L5 of the calling transmitting-Empfangssstation, it is assumed that just in the time interval of validity of the long-term key L2 repeated paging information 1, A; 2, A; 3, A; 4, A; 5, A; 6, A; 7 A and 8 A is performed. Each page information is hereby limited to the duration of a change period of the short-term key. Because of the time difference of the station clocks between the calling and called transmitting-receiving station is generated by the station clock of the called transmitting-receiving station during the period in which on the transmitting station of the long-term key L2 is valid, the long-term key L1. To put this in the timing diagrams particularly expresses the timing chart E1L, the reference numeral L1 and edged reference numeral L2 in the time diagram S1L. The same applies to other time charts of FIG. 3.

The called transmitting-receiving station is now trying to detect the incoming call information, which, however, does not succeed by means of the long-term key L1. As the timing chart E2L shows it therefore remains for a predetermined program during the following change period that is actually associated with the long-term key L2, the long-term key L1. The calling transceiver station transmits the call information 1, A; 2, A; 3, A; ... 8, A now S2L as the diagram shows, using the long term key L3. Because even now no detection of the call information to the called transceiver station is possible, it tries the next change period with the long-term key L4, which is indicated in the diagram E3L. The calling station has, as the timing chart shows S3L, now also changed to long-term key, and transmits the paging information using the long term key L4. Now, a detection of the paging information 7, and A 8, A is possible. The called station can now correct their station clock and adjust to the station clock the calling transceiver station. This situation is shown for the called transmitting-receiving station in the timing chart for the E4LK and refende station by the time chart S4LK. Both transceiver stations are now working at the same time using the long-term key L5. Instead of the long-term key L5 but can be switched and started to transfer the actual useful information at the beginning of the long-term key L5 associated change period already equal also the short-term key.

In cases where such a serial search process takes an undesirably long time, the incoming call information for detecting on the receiving transceiver station also of this long-term key immediately preceding and subsequent long-term key can simultaneously be made available in addition to the current here long-term key. For this purpose it is only necessary to issue the long-term key input to the key store of MR2 Rufemfängers RE of FIG. 2 correspondingly faster for the handover to the comparator.

Of course, from a time key in long mode use can be made also in the transmission of the actual useful information if this is to short information and is thereby ensured that each new is another long-term key is available to be transmitted brief information.

Industrial applicability

The process may be operating with time encryption radio systems everywhere apply, where high security is to be added to the security against intrusion by an interferer also already during the phase of the connection and where also taking into account possible larger time tolerances between the station clocks of the transmitting receiving stations of such a radio system of the connection can be carried out as quickly and safely.

List of reference numerals used in the drawing figures

<dl id="dl0002"><dt>SSG</dt><dd>Key signal generator</dd><dt>KWG</dt><dd>Characteristic encoder</dd><dt>SG</dt><dd>Basic key donors</dd><dt>R1</dt><dd>Days key register</dd><dt>SR</dt><dd>key calculator</dd><dt>MD1,2,3</dt><dd>Mixer (modulo 2 adder)</dd><dt>SF</dt><dd>Key sequence memory</dd><dt>EV</dt><dd>Station clock-adjusting</dd><dt>G</dt><dd>quartz generator</dd><dt>TK</dt><dd>central clock</dd><dt>R2</dt><dd>Parameter storage (time, code number)</dd><dt>NE</dt><dd>Code number encoder</dd><dt>AST</dt><dd>flow control</dd><dt>U1,2,3</dt><dd>switch</dd><dt>S</dt><dd>transmitter</dd><dt>e</dt><dd>receiver</dd><dt>SIG</dt><dd>digital useful signal</dd><dt>SIG '</dt><dd>encrypted digital useful signal</dd><dt>T</dt><dd>clock</dd><dt>W</dt><dd>Duplexer</dd><dt>AT</dt><dd>antenna</dd><dt>ZE</dt><dd>Time information receiver</dd><dt>RE</dt><dd>pager</dd><dt>V</dt><dd>comparator</dd><dt>MR1,2</dt><dd>keystore</dd><dt>ZS</dt><dd>time key</dd><dt>i</dt><dd>time information</dd><dt>A</dt><dd>encrypted call address</dd><dt>i, A</dt><dd>call information</dd><dt>Kiv</dt><dd>Short-term key</dd><dt>Li</dt><dd>Long Key</dd></dl>