DE1762669A1 - Method and device for securing messages in telex connections against unlawful reception - Google Patents

Description

SIEMENS AKTIENGESELLSCHAFT Munich, the "XM. 1968

'ffittelsbacherplatz 2

^PA 68/2700

Method and device for securing messages in telex communications against unlawful receipt

The invention relates to a method and a device for securing messages in telex connections against unlawful reception, each message being one from a subscriber to a predetermined number of times nehmnr common center transferred subscriber ID goes ahead. .

To / Fdl

00983870619

BAD ORiGiNAL

ι / "79 - ² - 1762689

Particularly in the case of telex traffic with central units that are responsible for delivering any data stored in any way, etv / a a data processing system and serve to receive messages from a telex subscriber it is desirable to ensure the subscriber's call authorization.

For this purpose, the above is for a write connection mentioned type a method is provided in which according to the invention after sending one of at least one Teletype existing subscriber identification from a participant to the control center, this identification is geopcichert at the control center v / ird and a key unit with the basic key setting individually assigned to the subscriber in the Central unit is connected automatically so that by subsequently pressing a special triggering device (button) by the participant a Spruchschlüsscl both in the Key unit of the subscriber as well as - with simultaneous transmission to the control center - in the key unit the control center is entered so that the subscriber identification entered again at the subscriber is encrypted in this way becomes that one from an agreed basic key and from an automatically thrown saying key The key bit sequence formed is used for encryption and in the control center to decrypt the transmitted encrypted subscriber identifier is used and that this decrypted subscriber identifier with the as plain text transmitted and stored subscriber identification is compared. In this way it is with moderate effort on z. B. olcktronxchen tools both at the subscriber terminals as well as at the control center, a subscriber identification with high security against misuse and with largely to carry out automatic working method »A betrayal of key figures by the unqualified or careless

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BAD ORiGiNAL

Operating personnel is not possible.

Further details of the invention emerge from the

described below and shown in the drawing. Embodiments. It shows

1 shows a circuit arrangement with one of several subscriber terminals, via a dial-up network with a telex connection unit of a data processing system connected is,

Fig. 2 shows a variant of the arrangement of FIG. 1, with only the devices arranged at the subscriber station are shown.

In the arrangements according to FIGS. 1 and 2 v / jid a secret key number »the so-called basic key for an appointment Period, for example for a day, a week or a month, set in such a way that any bridges to a bridge switch BS to half adders / 'ückgeckkoppelter Shift register RS switched on or off »This Binary era. hl is in an encryption device either with switches that are not visible from the outside (buttons or plugsί set or is read in from a short strip of holes and saved electronically. During operation, the Participants for each '' saying "(in this case: request; a so-called "saying key", that is a second key number, which is automatically thrown by the encryption facility.

Both in the case of the subscriber end piece and in the case of the telex terminal unit the data processing system DVA is such an encryption device available that the subscriber identification number encrypted when entering and when entering data. Processing plant DVA decrypted. By comparison with the subscriber identification number previously sent as plain text

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recognizes the key device in the data processing system DVA that the subscriber's request is justified because the Kemi number was correctly encrypted ..

The following description of the mode of operation is the block diagram Pig. 1 is based. A subscriber terminal TE with a typewriter Ps and remote switching device PGT can Reach the connection unit PSK of the data processing system DVA via a Wählnotz V /. There sini. also a Remote switching device PGT and a chart recorder Ps provided for incoming and outgoing communication.

When a request is made, the subscriber selects the connection unit PSK of the data processing system DVA and assures itself by means of a "Y / er-da" query that it has reached the connection unit Has. Then he triggers his own name giver and then keys in his subscriber identification number (you can also Be part of the Naraengebers.) This is via a control valve ST stored in a subscriber identifier memory TKS and causes a subscriber key selector TSW to extract the key unit SE assigned to this subscriber from a to select the number of key units SE corresponding to the number of participants provided. The participant solves now his spell key by pressing a predetermined special key. He is from his key unit SE automatically generated and transmitted.

This key phrase is created by advancing the subscriber's own feedback shift register RS bis to release the mentioned special key and is fed back into the assigned feedback during the subsequent transfer

Shift register HS fed into the connection unit PSK. The basic key established by setting the bridge switch BS is with the subscriber and the data processing system

009838/0619

DVA identical, but different for each participant.

- The participant now gives his identification number again 'Keyboard off (or with name giver); it is clearly read along but issued in encrypted form. In doing so, the feedback generated Shift register RS the key bits that are in the mixer M through Half addition mod 2 with the information bits of the ternary characters "are mixed bit by bit and transmitted as encrypted characters.

Teletype characters arriving in the connection unit PSK of the data processing system DVA are now decrypted by means of the mixer M and the key bits from the feedback shift register RS. This results in the subscriber's identification number in plain text, which is compared with the one stored in the subscriber identification number memory TKS in a subscriber identification number comparator TKY.

If the comparison fails in the subscriber identification number comparator TKV positive, the participant was entitled to order; the following question is accepted. «Otherwise the connection is released; it can also be done beforehand by the Data processing system DVA a decision, for example an agreed abbreviation "INM" (identification not possible). This would take into account the fact that the participant is keying in his Kenn-Iiummer may have prescribed, or transfer was faulty.

For the aforementioned automatic key generation, the following details are given for the method of operation explained:

The binary information that circulates in the feedback shift register to generate the slogan key, as long as the '

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Special key ge, is pressed, comes from the previous operation with the connection unit or another participant. Only when starting operation for the first time after changing the doö basic key is it necessary to ^{enter any binary information 1 into} the empty shift register, which z. B. can be done by pressing the keyboard.

In order to be able to use the in the Transistors of the shift register to receive stored binary information, the key unit under Tension remains while the motor of the televoting machine Disconnected from the network via the remote switching device ο Single-_ borrowed when using toroidal cores as storage elements In the shift register, the key unit can be switched off with the telex typewriter.

The transmission of the generated key to the remote station takes place in the form of telex characters. It will the contents of the slide register in the teletype cycle into the mixer entered, which forwards it unchanged to the remote station with the addition of start-up and blocking steps. At the At the receiving station, the mixer hides the start-up and blocking steps and transfers the message key information to the shift register. Since at the sending point when the shift register is emptied, the information is fed back to the feedback Input is entered, it is retained. The end of the message key transmission is in the register of the receiving point the same information as long as the transmission went undisturbed.

The effect of the bridge switch is expediently y canceled during the process of transferring the slogan key. The teletypewriters write to transmission and Reception stollo with the transmitted key characters,

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so, if necessary, they provide help in locating the error. At the end of the slogan key transmission, the sending and receiving stations are automatically switched over on encrypted operation and the effect of the bridge switch is reactivated. ·

In the example discussed with a feedback shift register RS with 19 bit contains the key phrase four Telex character (1 bit unused). If you use irreducible primitive polynomials as basic conclusions (switch position in the bridge gate BS) for an optimal period of the key, so result j

27594 basic key options and 2 ⁿ -1 «2 ^ -5,2'1O ^{5 key words.} The period length of the key is also 5.2 "10. The probability that after 1000 sayings an in-phase, i.e. one started with the same key, is on average 1.9 * 1ο.

Individual sayings in the same phase lead to encryption security not, there is a break-in only when they occur more frequently possible in the key. You can add * \ var by adding further shift register positions or shift registers these Increase security at will. However, this does not seem appropriate here because of the effort involved and for safety reasons not mandatory.

Fig. 2 shows another arrangement of the subscriber station} die Execution of the counterpart in the connection unit FSK of the data processing system is accordingly. The basic one The mode of operation of this system differs from that described above according to FIG. 1 with regard to the encryption. Only plain text characters are used to generate a quasi-random η Bit sequence used with which the plain text is then encrypted will.

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In addition to the adjusted in the same way and changing basic key kpmmt for each telex a message key to the application of any by hitting keyboard keys generated at the transmitter site and is transmitted to the receiving point ι. After switching to encrypted operation, the shift register RS supplies a key bit for each information bit entered on the teleprinter, which is mixed with the plain text bit in the mixer M in order to generate the encrypted text to be transmitted.

In contrast to the method according to FIG. 1, however, over a half adder HA the encrypted bit sequence continuously mixed with the key bit sequence circulating in the shift register RS. Thus the key bit sequence also depends on the Clear text, since this is included as a component in the mixed pre-encrypted text.

Such a method is given a higher level of key security than that according to Fig. 1. Proverbs in the same phase, that is, started with the same key, also indicate Places where the plaintexts have the same characters, no matching encrypted characters. Conclusions on the plain text due to the frequency of letters cannot be drawn. This admixture of the encrypted. ton text (with plain text component) does the key bit sequence plain text dependent.

A receiving station can only decrypt correctly as long as it has received the encrypted characters correctly, because only then does the generation of your key bit sequence match that at the sending station. This is for the normal Teletype operation with long telex and on disturbed transmission routes is a disadvantage. For short inquiries to a Data processing system DVA on telex or dedicated lines

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ORIGINAL INSPECTED

PA 9/411/1179 -9- 176266

The small error ratio is enough for trouble-free operation the end. In any case, a data processing system DVA can only correctly answer a query that has been received completely undisturbed. The lagging error that occurs with plain text-dependent encryption due to a transmission fault ■ oinst.ellt, but leads to the fact that the data processing system DVA with the help of the formal check with incorrect inquiries with high security and immediately rejects it. So has this encryption method in cooperation with the system DVA the effect of an error-detecting system "

In summary, the following parameters are of which the encrypted text depends on, effective:. '

a) Basic key (consisting of the switch setting in

feedback shift register)

b) Any characters entered from the keyboard

follow at the beginning of the encrypted operation)

c) Encrypted telex characters used to form the Key must be consulted on an ongoing basis

d) plain text of the encrypted telex "

An exemplary embodiment is shown in FIG. 2 as a block diagram shown, on the left the teleprinter part with the usual teleprinter Fs and remote switching device FG-T and on the right the Key device.

The teleprinter modules Keypad Ta, tape reader Le, printer Dr with punch Lo _{0 are used for input and output} ■ LA

with key identifier iAu ^ vfiÄ-t »UQg - * _t SKA

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OBIQINAL

Transmit / receive switchover switch SEU

Stop-by-counter-write evaluator HGA

Key character counter SZ

Clock generator TG

A distinction must be made between the following 4 operating cases in operation:

CLEAR TEXT TRANSMISSION.

KEY SETTING

ENCRYPT

DECODING The mode of action is as follows:

KLARBETRIBB "

Local operation (without a line) can be carried out using a suitable remote switching device and is used for production of punched tapes using the keyboard and read-along text as well as for duplicating punched tapes and print texts. The operation Via the line Ltg is recorded with the help of the remote switching device. The participant communicates in clear operation nit the opposite station by means of keypad transmitter Ta and sheet printer Dr via control unit ST 1-2, line termination LA and ! Remote control device PGT. In this operating mode only the Speech key identifier evaluator SKA activated.

KEY SETTING

Certain initial conditions must be communicated to the key part for pre-encryption and decryption. It is zwisöien _n to distinguish the program, according to which the (or *) feedback shift register RS work and the initial position of the shift register. The shift register is programmed using the basic key, which is set by opening or closing certain switches in the bridge switch BS.

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All corresponding telex offices change the basic key at agreed times (daily, weekly or monthly). The starting position of the shift register Is defined by entering any telex characters using the keyboard before the encrypted operation begins

and changes with every telex.

TTiIi, a subscriber can switch from clear operation to key operation; so he first gives a sequence of characters that do not appear in the clear text (e.g. Zi page F), the so-called message key identifier. It is recognized in the key-key evaluator SKA, and this leads to a change in the controlled ST. Further characters sent by the keyboard run into the feedback shift register RS ala slogan key, both at the sending station and at the receiving station. Sending station: Ta, ST 1-3-4, RS, also ■■ -. * ■. ■ via ST 1-2, LA (SEU on

^ Send), FGT, Ltg zur

Opposite station. Receiving station: Ltg, FG5, IA (SEU on reception), ST 2-3-4tRS.

When entering this key phrase, the bits are the telex characters counted (slogan key counter SZ) and after the register RS is filled, the feedback circuit BS activated, the subscriber must have at least 3 telex characters . to fill the 19 digits of the register in the example. When using a larger register RS or more

accordingly more characters are required. The Circuit arrangement can also be made so that the input of the SchlÜssclbits in the ring shift register RS takes place via the Spruchkey counter SZ in such a way that the access and lock steps are not passed on | 4 slogan key times are then at least necessary.

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The sending participant makes after entering the slogan key pause and a green lamp lights up to inform you that the device is now on Key operation has switched. The same thing happens at the receiving station without the intervention of an operator.

LOCKED

When encrypting, plain text overflows from the telex Fs ST1-6 to the mixer circuit M. This on the other hand receives the Bit-wise output key text from the RS and transmits the encrypted text via ST 7-8, LA (SEIT to send), FGT on the line.

The half adder HA is coupled, on the one hand, to the output of the encrypted text, on the other hand, via ST 7-9 connected via ST 5-4 to the input side of the feedback shift register RS. The encrypted text is therefore added to the binary information circulating in RS. When sliding through the register RS changes This information is constantly updated depending on the setting of the bridge switch (basic key) and the mixed encrypted text that is dependent on the plaintext. Thus appears at the output of the shift register a quasi-random bit sequence that the mixer circuit M is fed.

The stations operate in encrypted mode until the end of the message; then is the exchange the namesake possible. Dudi release the 'close' button at the remote switching device FGT the connection is disconnected - Via the local line from the FGT to the cipher device is caused to be "encrypted" by the operating mode switches to "clear".

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■ MTSCHLÜSjäEIN

- After the connection from the remote station is in clear operation has been recorded, the switch to input of the Spruchschlüssol.s takes place automatically in that the key identifier evaluator SKA the final recognition (Sequence of characters "that does not appear in plain text, e.

'B. 4 x £ on the number side). The message key characters received run via Ltg, TGT, LA (SEU on reception) St 2-4 in the feedback shift register RS “You are counted from the key character counter SZ via ST 3-4.

During the pause that follows, the key device switches to "decrypt". By lighting up a green lamp this operating status is displayed. It serves as a warning now send characters if there is no request from the remote terminal this is available. In urgent cases, the sending of the remote station can be done by the "Hait-by-counter-letter evaluator" HGA) must be shut down. However, both stations switch back to clear operation, as explained later = ·

Incoming encrypted! Telex characters are translated ltg, PGT, LA (SEU on reception), ST 8-6 entered into the mixer circuit M. On the other hand, it receives the output binary Key bits from the shift register RS, that from the clock generator TG is controlled. The mixing circuit M now decrypts the teletype characters and sends them to the teletype via ST 7-1 Fs continue.

The encrypted text received is also transmitted via ST 8-9 fed to the half adder HA, which mixes it bit by bit via ST 5-4 into the bit sequence circulating in the shift register RS “So the information circulating in the shift register is constantly changed, but in the same way as that on the transmitting station “Die vom

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Shift register RS output to the mixer circuit M. Key bit sequence enables correct decryption as long as the transfer of the encrypted in- " formation takes place without errors.

The end of the encrypted operation is announced by the transmitting station caused by releasing the connection. Downshifting in clear mode on the receiving part in the same way as described for the sending point »

It can happen that one is in key operation receiving station wants to interrupt the transmission of the remote station, z. B. if the reception has become unclear. In normal It is common practice for television broadcasting to stop the remote transmitting station by writing back.

For this purpose, the key device has a "stop by counter-writing evaluator" HGA, which checks whether each blocking step is interrupted by a counter-letter when it is sent was. If that is the pail, the station is automatically switched to clear operation and the broadcast is interrupted » The receiving station then also switches to clear operation / un, either manually or with a receiving data processing system DVA by recognizing disturbed transmission with the help of the formal check.

2 Figures 8 claims

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Claims (7)

»9/411/1179 ^ -15- - .. Claims K Procedure for securing messages in telex connections against unlawful reception, with each message being transmitted by a subscriber to a central unit common to a number of predetermined subscribers Toilet identification precedes, characterized in that after sending a subscriber identifier consisting of at least one telex character from a subscriber to the control center this identifier is stored at the control center and a key unit with the subscriber individually assigned round key setting in the control center automatically is connected that by subsequent actuation of a special release device. (button) by the participant a saying key both in the participant's key unit , as well as - with simultaneous transmission to the "control center is entered into the key unit of the control center, that also the subscriber identification entered again at the subscriber It is encrypted in such a way that one is automatically diced from an agreed basic key and one Key bit sequence formed by the saying key is used for encryption and in the control center for decryption the transmitted encrypted subscriber identification is used and that this decrypted subscriber identifier with the part transmitted and stored as plain text ! luhmerkerung is compared. 2. The method according to claim 1, characterized by a quasi-random generation of the key phrase by switching on a subscriber's own feedback shift register (RS) for the duration of the actuation of the Spruchschlüsscltaste with subsequent transmission of the Spruchschlüsscls to the assigned key unit of the control center. 009838/0619 ORIGINAL INSPECTED 3. Device for performing the method according to claim 1 or 2, characterized by naming device-like means for the automatic output of subscriber characteristics. '> 4. Device for performing the method according to claim 1 or 2, characterized in that switching means for the key files are provided to enable the encrypted transmission of the messages. 5. The method according to claim 1 or 2, characterized in that the plain text in addition to the basic and the saying key influences the formation of the quasi-random key, that the encrypted text of the key information circulating in the feedback shift register is ongoing is admixed. 6. Device for performing the method according to the claims 2 and 5, characterized in that a mixing circuit sum mixing of plain text with the feedback Shift register (RS) output bits is provided. 7. The method according to claim 1, characterized by a qucsi-random generation of the saying key by Any number of characters is entered on the keyboard of the sending station and transmitted to the remote station, however, when entering the feedback shift registers of both stations, the start-up and blocking steps be hidden. S. The method according to claim 5, characterized in that the addition of the encrypted text to the key information circulating in the feedback shift register takes place with the suppression of start-up and locking steps. 009838/0619 Read 11 e