| 6570988 |
Simple technique for implementing a cryptographic primitive using elementary register operations |
| May-27-2003 |
A technique which implements a primitive for computing, e.g., a checksum. Specifically, this primitive replaces a mod(M) operation with a series of simple elementary register operations. These operations... |
| 5991416 |
Scrambling and descrambling circuit for a cordless telephone |
| Nov-23-1999 |
A scrambling and a descrambling circuit for cordless telephone provides a higher security level than current phone scrambling circuitry. The higher security level is accomplished by separating an audio... |
| 5796838 |
Method and apparatus for performing frequency spectrum inversion |
| Aug-18-1998 |
An apparatus and method for creating voice privacy by performing frequency spectrum inversion in electronic voice transmission systems includes the steps of digitizing an analog signal and inverting the... |
| 5471531 |
Method and apparatus for low cost audio scrambling and descrambling |
| Nov-28-1995 |
Audio signals are descrambled by double sideband modulating the scrambled audio signal with a modulation carrier having a carrier frequency slightly above the highest audio signal present in the scrambled... |
| 5446795 |
Universal decoder for television signal scramble systems |
| Aug-29-1995 |
A universal decoder for scrambled television signals in which the signals are processed in a circuit by converting them to other frequencies and then removing the scrambling signal. One method uses one... |
| 5235640 |
Master decoder for television signal scramble systems |
| Aug-10-1993 |
A master decoder for scrambled television signals in which the signals are processed in a circuit by converting them to other frequencies and then removing the scrambling signal. One method uses one or... |
| 5150401 |
Retrofittable encryption/decryption apparatus using modified frequency modulation |
| Sep-22-1992 |
A communication system for providing secured communication over a communication channel. The system includes a DES encryption device and a DES decryption device retrofittable into or within a conventional... |
| 5065430 |
Voice band splitting scrambler |
| Nov-12-1991 |
Disclosed is a voice band splitting scrambler. To simplify the hardware thereof, the apparatus comprises a band splitting unit (11) for splitting an input voice signal into a plurality of band channels,... |
| 5018198 |
Speech privacy processing method and apparatus therefor |
| May-21-1991 |
A speech privacy processing apparatus is disclosed including: a unit for obtaining the number of coefficients commonly included in a set of coefficients obtained by Fourier transformation and corresponding... |
| 4984219 |
Method and apparatus for decoding of frequency inversion based scramblers |
| Jan-8-1991 |
A method and apparatus for decoding of frequency inversion based scramblers is disclosed. A quadrature amplitude modulation detector determines the frequency of the tone used for inverting the scrambled... |
| 4949378 |
Toy helmet for scrambled communications |
| Aug-14-1990 |
A toy helmet that permits the wearer to speak as to generate unintelligible noise so far as bystanders are concerned but which can be understood by another child wearing an identical helmet. Each helmet... |
| 4924512 |
Method and apparatus for preventing recognition of a telephone dialing signal |
| May-8-1990 |
A method and apparatus for preventing recognition by a telephone system of a telephone dialing signal which inverts at least a portion of the telephone dialing signal in response to receiving the telephone... |
| 4817141 |
Confidential communication system |
| Mar-28-1989 |
The respective feature parameters extracted from a speech signal is converted into the corresponding line spectrum data in a first frequency band obtained by dividing the speech signal frequency band.... |
| 4802219 |
Method and apparatus for distorting a speech signal |
| Jan-31-1989 |
Method of distorting a speech signal by rearranging and/or reversing frequency bands in this signal. The speech signal is divided into a plurality of sub-bands by filtering, and the sub-bands are individually... |
| 4799257 |
Wireless transmission system for PM modulation signal |
| Jan-17-1989 |
A wireless transmitter for PM (phase modulation) signal with a spectrum scrambler for relocation of input spectrum for privacy purposes is comprised of a differential circuit coupled with an input terminal,... |
| 4790009 |
Scrambler system |
| Dec-6-1988 |
A scrambler system comprises in a transmitter part thereof as oscillator circuit for generating a local oscillation signal, a frequency dividing circuit for obtaining a frequency divided signal by frequency-dividing... |
| 4773092 |
Speech scramblers |
| Sep-20-1988 |
A band scrambler which processes only time domain samples is described. The band scrambler has the effect of dividing the input signal spectrum into N sub-bands. The N sub-bands are permuted such that... |
| 4652699 |
Voice scrambler using frequency-inversion and band-splitting technique |
| Mar-24-1987 |
A spectrum inversion type voice scrambler for secret speech communication comprises a first spectrum inversion section, a second inversion section and an adder for summing the outputs of the first and... |
| 4623980 |
Method of processing electrical signals by means of Fourier transformations |
| Nov-18-1986 |
In order to upgrade input signals for further processing, one or more of the input signals is split up by a decimating technique into spectral component signals which are processed according to the desired... |
| 4232194 |
Voice encryption system |
| Nov-4-1980 |
An apparatus and method of voice encryption uses segment swapping. Features of the invention include weighting the input time-function segments by a Hamming or Hanning Window function, before converting... |
| 4195202 |
Voice privacy system with amplitude masking |
| Mar-25-1980 |
A voice privacy system enhances the privacy of a transmission by disguising the amplitude characteristics and cadence content of transmitted voice signals. Encoding apparatus first divides a voice signal... |
| 4188506 |
Method and installation for masked speech transmission over a telephone channel |
| Feb-12-1980 |
A method and an installation for masked or scrambled speech transmission utilize a time-scrambling unit for dividing the speech band into at least two sub-bands, for delaying the one sub-band with respect... |
| 4160875 |
Security system |
| Jul-10-1979 |
A security system for use in homes, hotels, businesses, schools, streets, and other locations requiring a high degree of security but where it is important to insure the privacy of the protected individual. |
| 4107470 |
Digital SSB-FDM communication system derived from a complex band-pass digital filter bank and by a filter breakdown process |
| Aug-15-1978 |
An SSB-FDM modulator derived from a complex band-pass digital filter bank and by a filter breakdown process comprises a discrete Fourier transform (DFT) processor capable of giving phase offsets to complex... |
| 4068094 |
Method and apparatus for the scrambled transmission of spoken information via a telephony channel |
| Jan-10-1978 |
A method of scrambling and unscrambling speech transmissions by first dividing the speech frequencies into two frequency bands and reversing their order by modulating the speech information, the width... |
| 4020285 |
Voice security method and system |
| Apr-26-1977 |
The specification discloses a voice scrambler technique wherein a voice signal is split into a plurality of discrete frequency sub-bands. A random code generator generates a randomized sequence of digital... |
| 4013837 |
Voice security method and system |
| Mar-22-1977 |
The specification discloses a voice scrambler technique wherein a voice signal is split into a plurality of discrete frequency sub-bands. A random code generator generates a randomized sequence of digital... |
| 3995115 |
Speech privacy system |
| Nov-30-1976 |
The communication of confidential information is generally accomplished by transforming applied message waves into an unintelligible form prior to transmission. Such a transformation may be accomplished... |
