Fourier masking analog signal secure communication system
US4393276A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 19, 1981 |
| Grant date | Jul 12, 1983 |
| Priority date | — |
| Expiry date | Mar 19, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04K1/04
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
The present invention relates to a secure communication system for analog signals which preserves the bandwidth of the original message signal by employing scrambling, or masking, techniques in the frequency domain instead of the time domain. At the transmitting end, the message signal x.sub.a (t) is sequentially passed through a Fourier transform processor (12) and a scrambling arrangement (14) before being masked to form a secure Fourier transform sequence X.sub.s (n). The secure message signal x.sub.s (t) is formed by passing the secure sequence X.sub.s (n) through an inverse Fourier transform processor (16) which produces a secure signal x.sub.s (t) comprising the same bandwidth as the original message signal x.sub.a (t). At the receiving end, the secure signal x.sub.s (t) is passed through a Fourier transform processor (22) and a descrambling arrangement (24) which performs the conjugate operation of the above-described scrambling arrangement, and "un-masks" the secure Fourier transform to reform the original Fourier transform X.sub.a (n). The original message signal x.sub.a (t) is recovered by passing the Fourier transform X.sub.a (n) through an inverse Fourier transform proc…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.