EP0042587B1 - Verfahren zur Umformung von für die verschlüsselte Übertragung in Signalabschnitte unterteilten Sprachsignalen sowie Vorrichtung zur Ausführung des Verfahrens - Google Patents

Verfahren zur Umformung von für die verschlüsselte Übertragung in Signalabschnitte unterteilten Sprachsignalen sowie Vorrichtung zur Ausführung des Verfahrens 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
Authority
EP
European Patent Office
Prior art keywords
signal
storages
group
segments
switching means
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP81104666A
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German (de)
English (en)
French (fr)
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EP0042587A1 (de
Inventor
Caflisch Dr. Mengia
Richard Dr. Weber
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CRYPTO AG
Original Assignee
CRYPTO AG
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Filing date
Publication date
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Priority to AT81104666T priority Critical patent/ATE7993T1/de
Publication of EP0042587A1 publication Critical patent/EP0042587A1/de
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Publication of EP0042587B1 publication Critical patent/EP0042587B1/de
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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

Definitions

  • 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)
EP81104666A 1980-06-20 1981-06-17 Verfahren zur Umformung von für die verschlüsselte Übertragung in Signalabschnitte unterteilten Sprachsignalen sowie Vorrichtung zur Ausführung des Verfahrens Expired EP0042587B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT81104666T ATE7993T1 (de) 1980-06-20 1981-06-17 Verfahren zur umformung von fuer die verschluesselte uebertragung in signalabschnitte unterteilten sprachsignalen sowie vorrichtung zur ausfuehrung des verfahrens.

Applications Claiming Priority (2)

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

Publications (2)

Publication Number Publication Date
EP0042587A1 EP0042587A1 (de) 1981-12-30
EP0042587B1 true EP0042587B1 (de) 1984-06-13

Family

ID=4282095

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81104666A Expired EP0042587B1 (de) 1980-06-20 1981-06-17 Verfahren zur Umformung von für die verschlüsselte Übertragung in Signalabschnitte unterteilten Sprachsignalen sowie Vorrichtung zur Ausführung des Verfahrens

Country Status (10)

Country Link
EP (1) EP0042587B1 (no)
JP (1) JPS5729100A (no)
AR (1) AR228273A1 (no)
AT (1) ATE7993T1 (no)
BR (1) BR8103891A (no)
DE (1) DE3164136D1 (no)
DK (1) DK271481A (no)
ES (1) ES8303853A1 (no)
FI (1) FI811862L (no)
NO (1) NO812082L (no)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59111441A (ja) * 1982-12-17 1984-06-27 Sony Corp 音声信号の秘話方式
JPS59127442A (ja) * 1983-01-11 1984-07-23 Sony Corp 音声信号の秘話方式
FR2541060B1 (fr) * 1983-02-16 1989-02-03 Electroniques Et Const Procede de brouillage d'informations a transmettre d'un poste emetteur a un poste recepteur
EP0219559B1 (de) * 1985-10-17 1990-09-05 ANT Nachrichtentechnik GmbH Mobilfunksystem für die Übertragung sowohl digitaler als auch analoger Signale
FR2625391A1 (fr) * 1987-12-23 1989-06-30 Radiotechnique Ind & Comm Procede et systeme de brouillage/desembrouillage du son
JPH0314853U (no) * 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 (de) * 1978-08-04 1980-02-21 Siemens Ag Anordnung zur durchfuehrung einer verschleierten uebertragung von informationen

Also Published As

Publication number Publication date
DK271481A (da) 1981-12-21
JPS5729100A (en) 1982-02-16
BR8103891A (pt) 1982-03-09
NO812082L (no) 1981-12-21
ES503158A0 (es) 1983-02-01
FI811862L (fi) 1981-12-21
ES8303853A1 (es) 1983-02-01
AR228273A1 (es) 1983-02-15
EP0042587A1 (de) 1981-12-30
ATE7993T1 (de) 1984-06-15
DE3164136D1 (en) 1984-07-19

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