Method and system for secure telecommunications

Details Method and system for secure telecommunications Method and system for secure telecommunications

1991-05-24

1993-01-05

Tarcza, Thomas H.

Cryptography

Cryptanalysis

380 41, 380 49, H04K 100

Patent

active

051777851

ABSTRACT:
There is disclosed a method and system for injecting a number of different signal patterns onto a tone encoded telecommunications line for the purpose of preventing unauthorized eavesdropping. The system relies upon the use of an unused column frequency of the DTMF signals and a notched filter to remove that frequency from received transmission. The second technique is the insertion of precise levels of three valid tones. A third method is the modulation of all of the tones yielding side tones which are also in the valid range, and a fourth method is by sending random signature tones on the line, thereby preventing tape recording and playback of the coded tone communcation.

REFERENCES:
patent: 4214126 (1980-07-01), Wipff
patent: 4972469 (1990-11-01), Saltwick et al.

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