EP0042587B1 - Method of transforming speech signals subdivided into signal segments for enciphered transmission, and apparatus for realizing this method - Google Patents

Method of transforming speech signals subdivided into signal segments for enciphered transmission, and apparatus for realizing this method Download PDF

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Publication number
EP0042587B1
EP0042587B1 EP81104666A EP81104666A EP0042587B1 EP 0042587 B1 EP0042587 B1 EP 0042587B1 EP 81104666 A EP81104666 A EP 81104666A EP 81104666 A EP81104666 A EP 81104666A EP 0042587 B1 EP0042587 B1 EP 0042587B1
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signal
storages
group
segments
switching means
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German (de)
French (fr)
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EP0042587A1 (en
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Caflisch Dr. Mengia
Richard Dr. Weber
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CRYPTO AG
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CRYPTO AG
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00—Secret communication
    • H04K1/06—Secret communication by transmitting the information or elements thereof at unnatural speeds or in jumbled order or backwards

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  • the invention relates to a method for reshaping voice signals divided into signal sections for the encrypted transmission, the individual signal sections being compressed in time by reading in and reading out from memories with different reading and reading speeds, and a device for carrying out the method.
  • Such a method and a device for carrying out the method are known from DE-A1-2834280. There, the time gaps caused by the time compression are filled with additional information in order to increase the level of security of the encryption.
  • the input signal to be encrypted is divided into sections.
  • the division can take place in terms of frequency or time or in both axes at the same time.
  • the signal sections obtained are permuted depending on the key.
  • the cipher then consists of a changed sequence of signal sections, with discontinuities occurring at the interfaces. Due to the finite band limit of the transmission channel, dispersion takes place. The joint is thus blurred, which results in a crosstalk between two adjacent signal gaps. If, in addition to the band limitation, the transmission channel also has group delay differences, which is the case in practically all applications, this effect can be increased drastically, since the settling process of such a channel takes longer.
  • the dispersion can have a significant impact on speech quality after decryption. As a rule, this causes a strongly disturbing impulsive noise.
  • None of the methods mentioned is suitable for eliminating the effects caused in particular by jumps in amplitude at the joints of signal sections in the analog transmission of voice signals in encrypted form.
  • the object of the present invention is to remedy the disadvantages arising from the method mentioned at the outset and to avoid signal discontinuities in the ciphertext, so that the interfering effects can be eliminated by means of a suitable evaluation on the receiving side.
  • analogue encryption of voice signals succeeds in increasing the voice quality after decryption.
  • the disruptive influences of the band limitation of the transmission channel are combated.
  • the basic idea of the method is that the signal is compressed in time and the time period thus obtained is used for double transmission of the critical signal components in the area of the joints (cf. FIG. 1).
  • the temporal compression and the associated increase in bandwidth are obtained by reading the signal to be processed into a memory at a specific speed and reading it out of it at an increased speed.
  • the signal components repeated in the period obtained can be provided with a weight function (cf. FIG. 4). With your help, a soft fade in and fade out can be realized. Only those signal components that have not been weighted are evaluated on the receiving side. Assembled correctly and stretched to the original length of time, they return the original signal.
  • weight function is specifically selected, no signal components are repeated. In this technically particularly simple case, no increase in bandwidth is prevented. In contrast, crosstalk between adjacent signal sections is also reduced here.
  • Fig. La shows a possible format of the speech signal to be encrypted.
  • the signal sections here have a bandwidth B and a time length T.
  • This signal is read into a memory at a certain speed and in permuted form Order read out at 1 / s times the speed.
  • each signal section T experiences a temporal compression to the length sT, the bandwidth B increasing to Bis.
  • Part of the information is read out a second time in the time periods thus obtained, the switching intervals T u (see FIGS. 1a and b). In this way, it can be prevented that discontinuities occur at the edges of the signal sections with the length T or sT, since the original signal curve is continued at these points during T u / 2.
  • the actual point of impact then occurs within the switching interval T u .
  • the signal part transmitted in the interval T u is blanked out in the receiver, since the entire information is contained in the remaining sections. These sections are read into the receiver-side memory at a certain speed and read out in reverse order at s times the speed (see FIG. 1c). The signal thus again receives the original bandwidth B.
  • the redundant signal component that is not required in the receiver and is transmitted in the switchover interval T u can be provided with a weighting function for transmission, which allows a switchover that is as smooth as possible and thus shortens the transient processes on the transmission channel.
  • Fig. 2 shows schematic sections of a cipher s (t) at a joint.
  • the blanking function is missing
  • the cipher is weighted in a "soft switching function.
  • FIG. 2c A special case is shown in FIG. 2c.
  • the technical implementation is particularly simple here, but the desired properties are only partially achieved.
  • FIG. 3 shows the block diagram of a possible implementation of the exemplary embodiment described.
  • the speech signal to be encrypted is limited to bandwidth B.
  • the signal is read into a memory group 4 via an analog-digital converter 2 and a switch arrangement 3. This reading process takes place according to the scheme shown in FIG. 4.
  • the soft switchover shown in FIG. 2b is realized with the aid of the amplifier 7.
  • the ciphertext is subsequently fed into the transmission channel via a transmission filter 8.
  • the control of the switches 3, 5 and of the variable amplifier 7 and the addressing of the memories 4 is carried out by a control unit 9.
  • the control unit 9 of the transmitter is capable of individually addressing or controlling the three memory parts and the switches of the switch arrangement 3 . By repeating an address sequence when reading out, the relevant signal section can be read out and transmitted a second time, so that the situation shown in FIG. 1 arises.
  • the signal reaches a storage group 13 via a reception filter 10, an analog-digital converter 11 and a changeover switch 12.
  • Fig. 4 gives an overview of the reading and reading rhythm in the transmitter and receiver.
  • control units 9 and 17 require the corresponding information for a key-dependent permutation of the signal blocks. This is provided by a key stream generator, which is not explained in more detail here.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
  • Time-Division Multiplex Systems (AREA)
  • Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)
  • Reduction Or Emphasis Of Bandwidth Of Signals (AREA)
  • Communication Control (AREA)

Description

Die Erfindung betrifft ein Verfahren zur Umformung von für die verschlüsselte Uebertragung in Signalabschnitte unterteilten Sprachsignalen, wobei die einzelnen Signalabschnitte durch Ein-und Auslesen in bzw. aus Speichern mit unterschiedlichen Ein- und Auslesegeschwindigkeiten zeitlich gestaucht werden, sowie eine Vorrichtung zur Durchführung des Verfahrens.The invention relates to a method for reshaping voice signals divided into signal sections for the encrypted transmission, the individual signal sections being compressed in time by reading in and reading out from memories with different reading and reading speeds, and a device for carrying out the method.

Ein solches Verfahren sowie eine Vorrichtung zur Durchführung des Verfahrens ist aus der DE-A1-2834280 bekannt. Dort werden die durch die zeitliche Stauchung entstehenden Zeitlücken mit Zusatzinformationen aufgefüllt, um dadurch den Sicherheitsgrad der Verschlüsselung zu erhöhen.Such a method and a device for carrying out the method are known from DE-A1-2834280. There, the time gaps caused by the time compression are filled with additional information in order to increase the level of security of the encryption.

Bei der Mehrzahl von analogen Sprachschlüsselverfahren wird das zu verschlüsselnde Eingangssignal in Abschnitte unterteilt. Die Aufteilung kann frequenzmässig oder zeitlich oder in beiden Achsen zugleich erfolgen. Die erhaltenen Signalabschnitte werden schlüsselabhängig permutiert. Das Chiffrat besteht dann aus einer veränderten Folge von Signalabschnitten, wobei an den Nahtstellen Diskontinuitäten auftreten. Infolge der endlichen Bandgrenze des Uebertragungskanals findet eine Dispersion statt. Die Stoßstelle wird also verwischt, was ein Uebersprechen zwischen zwei zeitlich benachbarten Signalanschnitten zur Folge hat. Weist der Uebertragungskanal neben der Bandbegrenzung noch Gruppenlaufzeitunterschiede auf, was in praktisch allen Anwendungen der Fall ist, so kann dieser Effekt noch drastisch verstärkt werden, da der Einschwingvorgang eines solchen Kanals länger dauert.In the majority of analog voice key methods, the input signal to be encrypted is divided into sections. The division can take place in terms of frequency or time or in both axes at the same time. The signal sections obtained are permuted depending on the key. The cipher then consists of a changed sequence of signal sections, with discontinuities occurring at the interfaces. Due to the finite band limit of the transmission channel, dispersion takes place. The joint is thus blurred, which results in a crosstalk between two adjacent signal gaps. If, in addition to the band limitation, the transmission channel also has group delay differences, which is the case in practically all applications, this effect can be increased drastically, since the settling process of such a channel takes longer.

Die Dispersion kann eine erhebliche Beeinträchtigung der Sprachqualität nach der Entschlüsselung bewirken. In der Regel tritt dadurch ein stark störendes impulsartiges Geräusch auf.The dispersion can have a significant impact on speech quality after decryption. As a rule, this causes a strongly disturbing impulsive noise.

Im Zusammehang mit der Uebertragung von Audiosignalen in zeitkomprimierter Form über Videokanäle ist aus der US-A-3 819 852 bekannt geworden, an den Rändern der entstehenden Signallücken eine Zusatzübertragung vorzunehmen. Ferner ist es bei Multiplexverfahren mit Zeitkompression gemäss Proceedings of the IEE, Band 111, Nr. 4, Seite 647 bis 668, bekannt, Lücken zwischen Signalgruppen derart durch Füllsignale auszufüllen, dass bei der Uebertragung eine ausgeglichene Energieverteilung erreicht wird. Schliesslich wird gemäss GB-A-1 407 196 bei einem Verfahren zum Aendern der Tonlage von Audiosignalen vorgeschlagen, die entstehenden Signallücken mittels Interpolation auszufüllen.In connection with the transmission of audio signals in time-compressed form via video channels, it has become known from US-A-3 819 852 to carry out an additional transmission at the edges of the signal gaps which arise. Furthermore, in multiplex methods with time compression according to Proceedings of the IEE, Volume 111, No. 4, pages 647 to 668, it is known to fill gaps between signal groups with fill signals in such a way that a balanced energy distribution is achieved during the transmission. Finally, according to GB-A-1 407 196, it is proposed in a method for changing the pitch of audio signals to fill the resulting signal gaps by means of interpolation.

Keines der genannten Verfahren ist geeignet, die insbesonders durch Amplitudensprünge an den Stoßstellen von Signalabschnitten bei der analogen Uebertragung von Sprachsignalen in verschlüsselter Form verursachten Effekte zu beseitigen.None of the methods mentioned is suitable for eliminating the effects caused in particular by jumps in amplitude at the joints of signal sections in the analog transmission of voice signals in encrypted form.

Die vorliegende Erfindung hat die Aufgabe, diese beim eingangs erwähnten Verfahren entstehenden Nachteile zu beheben und die Signalunstetigkeiten im Chiffrat zu vermeiden, so dass mittels geeigneter Auswertung auf der Empfangsseite die störenden Auswirkungen ausgeschaltet werden können.The object of the present invention is to remedy the disadvantages arising from the method mentioned at the outset and to avoid signal discontinuities in the ciphertext, so that the interfering effects can be eliminated by means of a suitable evaluation on the receiving side.

Diese Aufgabe wird durch die Merkmale gemäss den Ansprüchen 1 und 5 gelöst.This object is achieved by the features according to claims 1 and 5.

Dadurch gelingt es bei der analogen Verschlüsselung von Sprachsignalen, die Sprachqualität nach der Entschlüsselung zu erhöhen. Insbesondere werden die störenden Einflüsse der Bandbegrenzung des Uebertragungskanals bekämpft.As a result, analogue encryption of voice signals succeeds in increasing the voice quality after decryption. In particular, the disruptive influences of the band limitation of the transmission channel are combated.

Nachfolgend werden anhand der Zeichnungen die der Erfindung zugrundeliegenden Prinzipien sowie ein Ausführungsbeispiel näher erläutert. Es zeigen :

  • Figur 1a bis 1c drei schematische Bandbreite-Zeit-Diagramme zur Erläuterung des erfindungsgemässen Verfahrens ;
  • Figur 2a bis 2c drei schematische Amplituden-Zeit-Diagramme im Umschaltbereich zwischen zwei Signalabschnitten ;
  • Figur 3 ein Blockschema eines möglichen Ausführungsbeispiels der Erfindung ; und
  • Figur 4 ein Ablaufdiagramm mit der Ein- und Auslesefolge in die sende- bzw. empfangsseitigen Speicher.
The principles on which the invention is based and an exemplary embodiment are explained in more detail below with reference to the drawings. Show it :
  • Figure 1a to 1c three schematic bandwidth-time diagrams to explain the inventive method;
  • 2a to 2c show three schematic amplitude-time diagrams in the switching range between two signal sections;
  • Figure 3 is a block diagram of a possible embodiment of the invention; and
  • Figure 4 is a flowchart with the reading and reading sequence in the transmit or receive memories.

Die Grundidee des Verfahrens besteht darin, dass das Signal zeitlich gestaucht wird und der so gewonnene Zeitraum zur doppelten Uebertragung der kritischen Signalanteile im Bereich der Stoßstellen benutzt wird (vgl. Fig. 1). Die zeitliche Stauchung und die damit verbundene Erhöhung der Bandbreite erhält man, indem das zu verarbeitende Signal mit einer bestimmten Geschwindigkeit in einen Speicher eingelesen und mit erhöhter Geschwindigkeit daraus ausgelesen wird. Die im gewonnenen Zeitraum wiederholten Signalanteile können mit einer Gewichtsfunktion versehen werden (vgl. Fig. 4). Mit Ihrer Hilfe kann ein weiches Ein- und Ausblenden realisiert werden. Auf der Empfangsseite werden nur jene Signalanteile ausgewertet, die keine Gewichtung erfahren haben. Richtig zusammengesetzt und auf die ursprüngliche zeitliche Länge gedehnt, ergeben sie wieder das ursprüngliche Signal.The basic idea of the method is that the signal is compressed in time and the time period thus obtained is used for double transmission of the critical signal components in the area of the joints (cf. FIG. 1). The temporal compression and the associated increase in bandwidth are obtained by reading the signal to be processed into a memory at a specific speed and reading it out of it at an increased speed. The signal components repeated in the period obtained can be provided with a weight function (cf. FIG. 4). With your help, a soft fade in and fade out can be realized. Only those signal components that have not been weighted are evaluated on the receiving side. Assembled correctly and stretched to the original length of time, they return the original signal.

Bei spezieller Wahl der Gewichtsfunktion werden keine Signalanteile wiederholt. In diesem technisch besonders einfachen Fall verhindert man zwar keine Bandbreitenerhöhung. Dagegen wird auch hier das Uebersprechen zwischen benachbarten Signalabschnitten vermindert.If the weight function is specifically selected, no signal components are repeated. In this technically particularly simple case, no increase in bandwidth is prevented. In contrast, crosstalk between adjacent signal sections is also reduced here.

Im folgenden wird das Verfahren anhand des Beispiels einer einfachen Zeitpaketvertauschung erläutert. Fig. la zeigt ein mögliches Format des zu verschlüsselnden Sprachsignals. Die Signalabschnitte weisen hier eine Bandbreite B und eine zeitliche Länge T auf. Dieses Signal wird mit einer bestimmten Geschwindigkeit in einen Speicher eingelesen und in permutierter Reihenfolge mit 1/s-facher Geschwindigkeit ausgelesen. Dadurch erfährt jeder Signalabschnitt T eine zeitliche Stauchung auf die Länge sT, wobei die Bandbreite B auf Bis anwächst. In den dadurch gewonnenen Zeitabschnitten, den Umschaltintervallen Tu, wird ein Teil der Information ein zweites Mal ausgelesen (siehe Fig. 1a und b). Auf diese Weise kann verhindert werden, dass an den Rändern der Signalabschnitte mit der Länge T bzw. sT Unstetigkeiten auftreten, da an diesen Stellen der ursprüngliche Signalverlauf noch während Tu/2 fortgesetzt wird. Die eigentliche Stoßstelle tritt dann innerhalb des Umschaltintervalls Tu auf.In the following the method is explained using the example of a simple time packet exchange. Fig. La shows a possible format of the speech signal to be encrypted. The signal sections here have a bandwidth B and a time length T. This signal is read into a memory at a certain speed and in permuted form Order read out at 1 / s times the speed. As a result, each signal section T experiences a temporal compression to the length sT, the bandwidth B increasing to Bis. Part of the information is read out a second time in the time periods thus obtained, the switching intervals T u (see FIGS. 1a and b). In this way, it can be prevented that discontinuities occur at the edges of the signal sections with the length T or sT, since the original signal curve is continued at these points during T u / 2. The actual point of impact then occurs within the switching interval T u .

Der im Intervall Tu übertragene Signalteil wird im Empfänger ausgetastet, da ja die gesamte Information in den übrigen Abschnitten enthalten ist. Diese Abschnitte werden mit einer bestimmten Geschwindigkeit in den empfangsseitigen Speicher eingelesen und in rückvertauschter Reihenfolge mit s-facher Geschwindigkeit ausgelesen (siehe Fig. 1c). Das Signal erhält dadurch wieder die ursprüngliche Bandbreite B. Der im Empfänger nicht benötigte redundante Signalanteil, der im Umschaltintervall Tu übertragen wird, kann zur Uebertragung mit einer Gewichtungsfunktion versehen werden, welche eine möglichst weiche Umschaltung erlaubt und damit die Einschwingvorgänge auf dem Uebertragungskanal verkürzt.The signal part transmitted in the interval T u is blanked out in the receiver, since the entire information is contained in the remaining sections. These sections are read into the receiver-side memory at a certain speed and read out in reverse order at s times the speed (see FIG. 1c). The signal thus again receives the original bandwidth B. The redundant signal component that is not required in the receiver and is transmitted in the switchover interval T u can be provided with a weighting function for transmission, which allows a switchover that is as smooth as possible and thus shortens the transient processes on the transmission channel.

Fig. 2 zeigt schematische Ausschnitte eines Chiffrats s(t) an einer Stoßstelle. In Fig. 2a fehlt die Austastfunktion, in Fig. 2b ist das Chiffrat in einer « weichen Umschaltfunktion gewichtet. In Fig. 2c ist ein Spezialfall dargestellt. Hier ist die technische Realisierung besonders einfach, die erwünschten Eigenschaften werden aber nur teilweise erreicht.Fig. 2 shows schematic sections of a cipher s (t) at a joint. In Fig. 2a the blanking function is missing, in Fig. 2b the cipher is weighted in a "soft switching function. A special case is shown in FIG. 2c. The technical implementation is particularly simple here, but the desired properties are only partially achieved.

Fig. 3 zeigt das Blockschema einer möglichen Realisierung des beschriebenen Ausführungsbeispiels.3 shows the block diagram of a possible implementation of the exemplary embodiment described.

In einem Eingangsfilter 1 wird das zu verschlüsselnde Sprachsignal auf die Bandbreite B begrenzt. Ueber einen Analog-Digital-Wandler 2 und eine Schalteranordnung 3 wird das Signal in eine Speichergruppe 4 eingelesen. Dieser Einlesevorgang findet nach dem in Fig. 4 gezeigten Schema statt. Mit erhöhter Auslesegeschwindigkeit und in innerhalb eines Signalrahmens TR permutierter Reihenfolge gelangen die Signalabschnitte mit der Länge T (TR = n - T ; n ganzzahlig) über einen Umschalter 5 und einen Digital-Analog-Wandler 6 auf eine steuerbare Verstärkerstufe 7. Durch diesen Auslesevorgang erfährt das Signal die in Fig. 1a und b dargestellte Umformung. Dank dem überlappenden Einlesen zu Beginn und am Ende jedes Signalrahmens (vgl. Fig. 4) kann man das doppelte Auslesen derselben Signalausschnitte im Gebiete der Stoßstellen nicht nur innerhalb eines Rahmens, sondern auch am Anfang und Ende jedes Rahmens verwirklichen. Die in Fig. 2b gezeigte weiche Umschaltung wird mit Hilfe des Verstärkers 7 realisiert. Ueber einen Sendefilter 8 wird das Chiffrat hernach in den Uebertragungskanal eingespeist. Die Steuerung der Schalter 3, 5 und des variablen Verstärkers 7 sowie die Adressierung der Speicher 4 übernimmt eine Steuereinheit 9. Die Steuereinheit 9 des Senders ist dabei in der Lage, die drei Speicherteile und die Schalter der Schalteranordnung 3 einzeln zu adressieren bzw. zu steuern. Durch die Wiederholung einer Adreßsequenz beim Auslesen kann der betreffende Signalausschnitt ein zweites Mal ausgelesen und übertragen werden, so dass die in Fig. 1 gezeigte Situation entsteht.In an input filter 1, the speech signal to be encrypted is limited to bandwidth B. The signal is read into a memory group 4 via an analog-digital converter 2 and a switch arrangement 3. This reading process takes place according to the scheme shown in FIG. 4. With increased readout speed and in a sequence permuted within a signal frame T R , the signal sections with the length T (T R = n - T; n integer) reach a controllable amplifier stage 7 via a changeover switch 5 and a digital-analog converter 6 Reading out the signal undergoes the transformation shown in Fig. 1a and b. Thanks to the overlapping reading in at the beginning and at the end of each signal frame (cf. FIG. 4), it is possible to read out the same signal sections twice in the region of the joints not only within a frame, but also at the beginning and end of each frame. The soft switchover shown in FIG. 2b is realized with the aid of the amplifier 7. The ciphertext is subsequently fed into the transmission channel via a transmission filter 8. The control of the switches 3, 5 and of the variable amplifier 7 and the addressing of the memories 4 is carried out by a control unit 9. The control unit 9 of the transmitter is capable of individually addressing or controlling the three memory parts and the switches of the switch arrangement 3 . By repeating an address sequence when reading out, the relevant signal section can be read out and transmitted a second time, so that the situation shown in FIG. 1 arises.

Im Empfänger gelangt das Signal über einen Empfangsfilter 10, einen Analog-Digital-Wandler 11 und einen Umschalter 12 in eine Speichergruppe 13.In the receiver, the signal reaches a storage group 13 via a reception filter 10, an analog-digital converter 11 and a changeover switch 12.

Im Gegensatz zum Sender, wo drei Speicher eingesetzt werden, um auf einfache Weise das überlappende Auslesen des Chiffrats an den Rändern des Rahmens T zu ermöglichen, genügen im Empfänger zwei Speicher. Mit verkleinerter Auslesegeschwindigkeit und in rückvertauschter Reihenfolge werden die Signalabschnitte über einen Umschalter 14 und einen Digital-Analog-Wandler 15 einem Ausgangsfilter 16 zugeführt. Auch im Empfänger werden die Umschalter 12, 14 und die Adressierung der Speicher 13 von einer Steuereinheit 17 kontrolliert. Fig. 4 gibt einen Ueberblick über den Ein- und Ausleserhythmus im Sender und Empfänger.In contrast to the transmitter, where three memories are used in order to enable the cipher to be read out overlapping at the edges of the frame T in a simple manner, two memories are sufficient in the receiver. The signal sections are fed to an output filter 16 via a changeover switch 14 and a digital-to-analog converter 15 at a reduced readout speed and in reverse order. The changeover switches 12, 14 and the addressing of the memories 13 are also controlled by a control unit 17 in the receiver. Fig. 4 gives an overview of the reading and reading rhythm in the transmitter and receiver.

Für eine schlüsselabhängige Permutation der Signalblöcke benötigen die Steuereinheiten 9 und 17 die entsprechende Information. Diese liefert ein hier nicht näher erläuterter Schlüsselstromgenerator.The control units 9 and 17 require the corresponding information for a key-dependent permutation of the signal blocks. This is provided by a key stream generator, which is not explained in more detail here.

Mit dem erfindungsgemässen Verfahren gelingt es, die Sprachqualität nach der Entschlüsselung zu erhöhen und störende Einflüsse der Bandbegrenzung des Uebertragungskanals zu mildern.With the method according to the invention, it is possible to increase the speech quality after decryption and to mitigate disruptive influences of the band limitation of the transmission channel.

Claims (6)

1. Method for modifying speech signals divided into segments for ciphered transmission, wherein the individual signal segments (T) are compressed in time by reading them into storages and out of them with different rates, characterized in that the time intervals (Tu) obtained by said compression are used for the repeated transmission of the edge portions of each signal segment, such that the original signal is continued at the intersection of each segment of the ciphered signals and characterized in that the ciphered signal is combined with a weighting function within the intervals (Tu) obtained by said compression, such that in said intervals a desired switching function is generated.
2. Method of claim 1, characterized in that the weighting function is a steady function having a value of 1 at the beginning of each interval (Tu), decreasing then to a value of zero at the moment of switching over and thereafter increasing again to the value of 1 at the end of the interval (Tu).
3. Method of claim 1, characterized in that on the receiver end the intervals (Tu) are blanked-out and the remaining segments are extended to their original lenght in time.
4. Method of claim 3, wherein on the transmitter end a plurality of segments (T) are combined to form a signal frame (TR) and the ciphering process is carried out by interchanging the segments (T) within said signal frame in accordance with a key information, characterized in that the repeated transmission at the intersections of the signal frames is obtained by overlappingly reading them into different storages followed by sequentially reading them out at a higher rate and in that the repeated transmission at the intersections of the signal segments (T) located within said frame (TR) is provided by a repeated read-out of edge portions of the segments (T) and by a respective higher rate of read-out.
5. Apparatus for carrying out the method of claim 4, having a transmitter end device comprising an analog-to-digital converter (2) connected to the input of a group of storages (4) by a first switching means (3), a digital-to-analog converter (6) connected to said group of storages (4) by a second switching means (5) and a control unit (9), which is connected to both switching means (3, 5) and to the group of storages (4) to control the process of interchanging the signal segments and of the read-out at a higher rate characterized in that the group of storages (4) comprises at least three storages, wherein the first switching means (3) and the group of storages (4) are controlled by the control unit (9) to read the signal from the analog-to-digital converter (2) as overlapping signal frames alternatingly into one of the storages of the group (4) and to read out part of the signal segments twice at their intersections and characterized in that the digital-to-analog converter (6) is connected at its output to a controllable amplifier (7), which is controlled by said control unit (9).
6. Apparatus of claim 5 having a receiver end device comprising an analog-to-digital converter (11) connected by a third switching means (12) to the input of a group of storages (13) including at least two storages, a digital-to-analog converter (15) connected to the output of said group of storages (13) by a forth switching means (14) and a control unit (17), which is connected to the third and forth switching means (12, 14) and to the group of storages (13) to provide for the rearrangement of the interchanged signal segments and to control the read-out at a reduced rate, characterized in that the group of storages (13) is controllable by the control unit (17) such as to blank out the signal portions which have been repeatedly transmitted.
EP81104666A 1980-06-20 1981-06-17 Method of transforming speech signals subdivided into signal segments for enciphered transmission, and apparatus for realizing this method Expired EP0042587B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT81104666T ATE7993T1 (en) 1980-06-20 1981-06-17 METHOD FOR TRANSFORMING SPEECH SIGNALS, WHICH ARE DIVIDED INTO SIGNAL SECTIONS FOR ENCRYPTED TRANSMISSION, AND DEVICE FOR CARRYING OUT THE METHOD.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH476380 1980-06-20
CH4763/80 1980-06-20

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EP0042587A1 EP0042587A1 (en) 1981-12-30
EP0042587B1 true EP0042587B1 (en) 1984-06-13

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP81104666A Expired EP0042587B1 (en) 1980-06-20 1981-06-17 Method of transforming speech signals subdivided into signal segments for enciphered transmission, and apparatus for realizing this method

Country Status (10)

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EP (1) EP0042587B1 (en)
JP (1) JPS5729100A (en)
AR (1) AR228273A1 (en)
AT (1) ATE7993T1 (en)
BR (1) BR8103891A (en)
DE (1) DE3164136D1 (en)
DK (1) DK271481A (en)
ES (1) ES503158A0 (en)
FI (1) FI811862L (en)
NO (1) NO812082L (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59111441A (en) * 1982-12-17 1984-06-27 Sony Corp Privacy telephone system of sound signal
JPS59127442A (en) * 1983-01-11 1984-07-23 Sony Corp Scrambling system for voice signal
FR2541060B1 (en) * 1983-02-16 1989-02-03 Electroniques Et Const METHOD OF INTERFERING INFORMATION TO BE TRANSMITTED FROM A TRANSMITTING STATION TO A RECEIVING STATION
EP0219559B1 (en) * 1985-10-17 1990-09-05 ANT Nachrichtentechnik GmbH Mobile radio system for the transmission of digital as well as analogous signals
FR2625391A1 (en) * 1987-12-23 1989-06-30 Radiotechnique Ind & Comm METHOD AND SYSTEM FOR INTERFERING / UNLOCKING SOUND
JPH0314853U (en) * 1989-06-28 1991-02-14

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1407196A (en) * 1971-11-16 1975-09-24 British Broadcasting Corp Apparatus for changing signal pitch
US3819852A (en) * 1972-08-29 1974-06-25 P Wolf Method of reducing the interference signals during the transmission of af signals in time-compressed form
DE2834280A1 (en) * 1978-08-04 1980-02-21 Siemens Ag Scrambled speech transmission system - divides signals into time elements which are rearranged and read out at higher speed and gaps filled with additional signals

Also Published As

Publication number Publication date
EP0042587A1 (en) 1981-12-30
NO812082L (en) 1981-12-21
ATE7993T1 (en) 1984-06-15
ES8303853A1 (en) 1983-02-01
ES503158A0 (en) 1983-02-01
DE3164136D1 (en) 1984-07-19
DK271481A (en) 1981-12-21
AR228273A1 (en) 1983-02-15
FI811862L (en) 1981-12-21
BR8103891A (en) 1982-03-09
JPS5729100A (en) 1982-02-16

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