EP0156428A1 - System zur geheimen Sprachübertragung für Schmalbandverbindungen - Google Patents

System zur geheimen Sprachübertragung für Schmalbandverbindungen Download PDF

Info

Publication number
EP0156428A1
EP0156428A1 EP85200353A EP85200353A EP0156428A1 EP 0156428 A1 EP0156428 A1 EP 0156428A1 EP 85200353 A EP85200353 A EP 85200353A EP 85200353 A EP85200353 A EP 85200353A EP 0156428 A1 EP0156428 A1 EP 0156428A1
Authority
EP
European Patent Office
Prior art keywords
bits
packets
pseudo
random code
spectrum
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.)
Withdrawn
Application number
EP85200353A
Other languages
English (en)
French (fr)
Inventor
Hervé Hillion
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.)
Telecommunications Radioelectriques et Telephoniques SA TRT
Koninklijke Philips NV
Original Assignee
Telecommunications Radioelectriques et Telephoniques SA TRT
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Telecommunications Radioelectriques et Telephoniques SA TRT, Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Telecommunications Radioelectriques et Telephoniques SA TRT
Publication of EP0156428A1 publication Critical patent/EP0156428A1/de
Withdrawn legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00—Secret communication

Definitions

  • the present invention relates to a cryptographic system for narrowband speech signals and, more particularly, to a pseudo-random cryptophonic system applying to analog speech signals having a bandwidth of 0.3 to 3.3 kHz approximately.
  • Pseudo-random digital cryptographic systems have already been proposed.
  • unencrypted or "clear” digital data is applied to an encryption unit.
  • a pseudo-random bit stream called "keyword” is produced by a first pseudo-random code generator and it is also applied to the encryption unit.
  • the encryption unit encrypts the clear text data in response to the keyword, for example by adding modulo 2 the bits of the same rank of the clear sequence and the keyword to generate an encrypted and unintelligible digital stream.
  • This encrypted digital stream is transmitted by cable or radio link to a decryption unit.
  • a second pseudo-random code generator produces a reception key word identical to the transmission key word. This reception key word is used for decryption of the encrypted data transmitted.
  • the decrypted data are then available for normal use.
  • the first and second pseudo-random code generators at each end of the link must be identical and synchronous, i.e. start at the same operating point in their cycle so that identical key words are produced at each station and at all times.
  • the speech signal is processed digitally in the transmitting and receiving stations, but it is transmitted analogically on the transmission channel.
  • the encryption and decryption devices can therefore be inserted online on non-encrypted preexisting links without modification of the latter.
  • Radiotelephone links for example can be made secret without modification other than the online insertion of the devices of the invention.
  • the transmitting and receiving stations each comprise a pseudo-random code generator and an audio frequency synchronization signal is transmitted from the transmitting station to the receiving station to synchronize the two generators. pseudo-random code.
  • the speech signal is digitized by an analog to digital converter and the digital signal obtained is divided into frames each comprising a certain number of bit packets. These packets are put in memory, then under the command of the generator of pseudo-random code of emission, the ranks of the packets in the frame are swapped. Still under the control of the pseudo-random code generator, the permuted packets are read in one direction or in the opposite direction, then, after being made analog by a digital analog converter, they are subject or not subject to a spectrum inversion.
  • the frequency of the carrier signal with respect to which the spectrum inversion is carried out is the same as that of the signal used for the synchronization of the pseudo-random code generators.
  • the analog signals are digitized by an analog-to-digital converter, then the data obtained are stored in packets.
  • the pseudo-random code generator Under the control of the pseudo-random code generator, the inverse permutation of that is carried out; used for transmission, then the bits of the packets are written in memory, either in the normal order of scanning, or in reverse order, depending on whether the transmission was made in the direct direction or in the opposite direction. Finally, a spectrum inversion is made or not on the data which have again become analog according to whether or not a spectrum inversion had taken place on transmission.
  • the number of encryption combinations is:
  • the speech signal having a bandwidth of approximately 300-3,300 Hz is picked up by a microphone 1 and digitized in an analog-to-digital converter such as, for example, a modulator A, 2, followed by a suitable filter 3.
  • the digital speech stream is divided into 53.3 ms frames composed of eight 213 bit packets with a duration of 6.66 ms, and the packets are stored in the primary memory 5 via a microprocessor 6 .
  • the packets stored in memory 5 are swapped under the control of the pseudo-random code generator 7 via the microprocessor 6.
  • the swapped packets are stored in secondary memory 10, then they are converted into analog signals by a digital analog converter 11, for example a demodulator A, followed by a low-pass filter 12.
  • the pseudo-random code generator 7 is a suitably looped five-bit shift register 71.
  • Pseudo-random code generators are well known in the art and are for example described in the work "Theory and Application of Digital Signal Processing" by Lawrence R. RABINER and Bernard GOLD, pages 565-567.
  • Bits 1, 2 and 3 are used for swapping packets in the frame.
  • Bit 4 is used to control the inversion of spectrum and bit 5 is used to control the inversion of reading of the packets in the memory 10.
  • the register 71 advances at the frame frequency of 18.75 Hz.
  • the encrypted analog speech signals and the carrier f 0 are added to the AND analog gate, 14.
  • the resulting signal is applied to the spectrum inverter 15.
  • the latter therefore reverses the spectrum 300 - 3 300 Hz with respect to the frequency 3600 Hz, i.e. the components at frequencies 300 Hz and 3,300 Hz become the components at frequencies 3,300 Hz and 300 Hz respectively.
  • the spectrum inverter 15 is connected to the output terminal of the transmission encryption device. This terminal 16 is connected either to a subscriber line or to a radio frequency channel.
  • the analog signal emitted by the encryption device of FIG. 1 is applied to the input terminal 46 of the decryption device and from there, via a spectrum inverter 45, to an analog-to-digital converter 32 followed by a low-pass filter 33 and to a modem 43
  • the analog to digital converter 32 can be a modulator A.
  • the modem output signal at frequency f 0 is applied to a voltage controlled oscillator, VCO 47 set to f H and to spectrum invertor 45.
  • VCO 47 drives the analog to digital converter at frequency f E 32 via a frequency divider 39.
  • the filter 33, the voltage-controlled oscillator 47, the pseudo-random code generator 37 and the primary memory 35 are connected to a microprocessor 36.
  • the latter is connected to a secondary memory 40, to a digital analog converter 41, for example, to the demodulator ⁇ -1 and to the spectrum inverter 45.
  • the latter receives from the microprocessor 36 the inversion or non-inversion commands and from the modem 43 the carrier at the frequency f 0 .
  • the decryption device Under the control of the five flip-flops of the shift register 371 mounted as a pseudo-random code generator, the decryption device performs a permutation of the packets, inverse to the permutation which took place on transmission, stores the bits of the packets in in the forward or reverse direction and controls the spectrum inversion.
  • the output of the decryption device is connected to a listener 31.
  • Fig. 3 shows a circuit which can be used as a spectrum invertor. It includes a differential amplifier consisting of transistors 151 and 152 whose emitters are interconnected across a constant current source 153. Such a circuit is known in the art and is for example described in the work "Differential Amplifiers" by LJ GIACOLETTO, Ed. WILEY -INTERSCIENCE, page 71, Fig. 5.2.
  • the emitter of transistor 151 is connected to the output of the gate AND 14 t and the emitter of transistor 153 is connected to the modem 13.
  • the inversion control or noninverting spectrum is made through the transistor 154 which courcircuite or not transistor 153.
  • the spectrum inverter is connected to a low-pass filter 155 whose output 16 is the output of the encryption device.
  • the pseudo-random code generator comprises three bits for the permutation of the packets in the frame. We could of course devote 4 or more than 4 bits to packet permutation, which would increase the number of possible combinations.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
EP85200353A 1984-03-13 1985-03-11 System zur geheimen Sprachübertragung für Schmalbandverbindungen Withdrawn EP0156428A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8403812A FR2561473A1 (fr) 1984-03-13 1984-03-13 Systeme de cryptophonie pour des liaisons a largeur de bande etroite
FR8403812 1984-03-13

Publications (1)

Publication Number Publication Date
EP0156428A1 true EP0156428A1 (de) 1985-10-02

Family

ID=9301962

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85200353A Withdrawn EP0156428A1 (de) 1984-03-13 1985-03-11 System zur geheimen Sprachübertragung für Schmalbandverbindungen

Country Status (5)

Country Link
EP (1) EP0156428A1 (de)
JP (1) JPS60208132A (de)
AU (1) AU3971385A (de)
DK (1) DK106985A (de)
FR (1) FR2561473A1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0250661A1 (de) * 1986-06-25 1988-01-07 FREDERIKSEN & SHU LABORATORIES, INC. Fernsehübertragungssystem mit Zeitverzerrungsverschlüsselung
FR2606237A1 (fr) * 1986-10-31 1988-05-06 Trt Telecom Radio Electr Dispositif de cryptophonie analogique a permutations dynamiques de bande
EP0356200A1 (de) * 1988-08-24 1990-02-28 Screen Electronics Limited Videoverschlüsselungssystem

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1983001717A1 (en) * 1981-11-04 1983-05-11 Mccalmont, Arnold, M. Privacy communication system employing time/frequency transformation
FR2530101A1 (fr) * 1982-07-06 1984-01-13 Thomson Brandt Procede et systeme de transmission cryptee d'un signal, notamment audio-frequence

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1983001717A1 (en) * 1981-11-04 1983-05-11 Mccalmont, Arnold, M. Privacy communication system employing time/frequency transformation
FR2530101A1 (fr) * 1982-07-06 1984-01-13 Thomson Brandt Procede et systeme de transmission cryptee d'un signal, notamment audio-frequence

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
INTERNATIONAL CONFERENCE ON COMMUNICATIONS, ICC '80, CONFERENCE RECORD, 8-12 juin 1980, Seattle, WA., vol. 1, pages 16.6.1 - 16.6.5, IEEE, New York, US; N.S. JAYANT et al.: "A comparison of four methods for analog speech encryption" *
PROCEEDINGS OF THE 1980 CARNAHAN CONFERENCE ON CRIME COUNTERMEASURES, 14-16 mai 1980, Lexington, Kentucky, pages 27-37; S. UDALOV: "Analog voice privacy with a microprocessor" *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0250661A1 (de) * 1986-06-25 1988-01-07 FREDERIKSEN & SHU LABORATORIES, INC. Fernsehübertragungssystem mit Zeitverzerrungsverschlüsselung
FR2606237A1 (fr) * 1986-10-31 1988-05-06 Trt Telecom Radio Electr Dispositif de cryptophonie analogique a permutations dynamiques de bande
EP0270147A1 (de) * 1986-10-31 1988-06-08 Thomson-Trt Defense Analoge Verschlüsselungseinrichtung mit dynamischer Bandvertauschung
EP0356200A1 (de) * 1988-08-24 1990-02-28 Screen Electronics Limited Videoverschlüsselungssystem

Also Published As

Publication number Publication date
DK106985D0 (da) 1985-03-08
JPS60208132A (ja) 1985-10-19
DK106985A (da) 1985-09-14
AU3971385A (en) 1985-09-19
FR2561473A1 (fr) 1985-09-20

Similar Documents

Publication Publication Date Title
KR960008610B1 (ko) 통신 보안용 아날로그 오디오 주파수 대역 스크램블러 및 그 방법
US3610828A (en) Privacy communication system
JPH09501291A (ja) 音声伝送における音声スクランブリングおよびアンスクランブリングのためのプロセスおよび装置
US4188506A (en) Method and installation for masked speech transmission over a telephone channel
KR100757715B1 (ko) 코드분할 다중 접속 채널을 이용한 고속 데이터 송수신을위한 방법 및 장치
JPH07245597A (ja) スペクトラム拡散通信方法及び送受信装置
EP0641096B1 (de) Verfahren mit mehrfachem Zugang durch Einteilung in orthogonale Frequenzen, entsprechende zentrale Station, entfernte Station, System und deren Verwendung
GB2132857A (en) Voice encryption and decryption system
US4636854A (en) Transmission system
EP0156428A1 (de) System zur geheimen Sprachübertragung für Schmalbandverbindungen
EP0188030A2 (de) Verfahren zur Kodierung und Dekodierung von Audioinformationen und Vorrichtung zur Durchführung des Verfahrens
EP0018869A1 (de) Anlage zur Verschleierung und Entschleierung eines Analogsignals durch zeitliche Kompressionen und Expansionen
US5598471A (en) Method and apparatus for encoding and decoding of audio transmission signals
EP0305261B1 (de) Verfahren zur schnellen Synchronisation von Vocodern, welche mittels Verschlüsselungs- und Entschlüsselungseinrichtungen verbunden sind
FR2530101A1 (fr) Procede et systeme de transmission cryptee d'un signal, notamment audio-frequence
EP0725544B1 (de) Verfahren zum Versetzen eines Verschlüsselers für Fernsehsignale
EP0216595A2 (de) Datenverschlüsselung
JPS6039941A (ja) 音声秘話装置及び方法
EP0129299A2 (de) Sicheres Fernsehübertragungssystem
EP0105906A1 (de) Audioverschlüssler mit einem hilfskanal zum synchronisieren des entschlüsslers
EP0228455A1 (de) Verwürfelungsvorrichtung
JPH0256188A (ja) スクランブル方法及び伝送装置
JPS6037585A (ja) デ−タ帰還型暗号装置
JPS63121335A (ja) 秘密通信方式
JPH055209B2 (de)

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): BE CH DE FR GB IT LI NL SE

17P Request for examination filed

Effective date: 19860310

17Q First examination report despatched

Effective date: 19870821

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19880319

RIN1 Information on inventor provided before grant (corrected)

Inventor name: HILLION, HERVE