System and method for encrypting a voice signal
First Claim
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1. A method of encrypting an input signal, comprising:
- filtering said input signal to provide a signal in a first path, having frequency components in a first band, and a signal in a second path having frequency components in a second band which is largely different from said first band;
shifting the frequency composition in at least one of said paths so that the frequency components in one of the paths lie in a band which substantially overlaps the band occupied by the frequency components of the other path, said shifting including inverting the frequency composition in at least one of said paths so that frequency components which were at higher frequencies before inversion are at lower frequencies after inversion, and components which were at lower frequencies are at higher frequencies; and
intermixing time segments of signals from said first and second paths, in a rearranged, randomized time sequence, including expanding the frequency composition of the intermixed time segments so that the collection of said intermixed segments exhibits greater bandwidth.
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Abstract
A system and method are disclosed for encrypting a voice signal. The input signal is filtered to provide a signal in a first path with components in a higher frequency band and a signal in a second path with components in a lower frequency band. Analog-to-digital conversion is carried out at a rate such that the frequency composition of the higher frequency path is inverted and shifted into the lower frequency band. Signals from the two paths are intermixed and converted to analog form at a rate greater than twice the rate of analog-to-digital conversion, so as to provide a randomized sequence of time segments of signals from the two paths, interspersed with gaps.
131 Citations
18 Claims
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1. A method of encrypting an input signal, comprising:
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filtering said input signal to provide a signal in a first path, having frequency components in a first band, and a signal in a second path having frequency components in a second band which is largely different from said first band; shifting the frequency composition in at least one of said paths so that the frequency components in one of the paths lie in a band which substantially overlaps the band occupied by the frequency components of the other path, said shifting including inverting the frequency composition in at least one of said paths so that frequency components which were at higher frequencies before inversion are at lower frequencies after inversion, and components which were at lower frequencies are at higher frequencies; and intermixing time segments of signals from said first and second paths, in a rearranged, randomized time sequence, including expanding the frequency composition of the intermixed time segments so that the collection of said intermixed segments exhibits greater bandwidth. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of encrypting an analog input signal, comprising:
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filtering said input signal to provide a signal in a first path, having frequency components in a higher frequency band, and a signal in a second path having frequency components in a lower frequency band; deriving digital samples from the signal in the first path at a first rate and from the signal in the second path at the same rate, to invert the frequency composition in said first path so that frequency components which were at higher frequencies before inversion are at lower frequencies after inversion and components which were at lower frequencies are at higher frequencies, and to shift the higher band frequency components in said first path to lie in said lower band; and intermixing segments of the samples on said first and second paths and converting to analog form at a rate greater than twice said first rate to provide a sequence of rearranged, randomized time segments of signals from said first and second paths, including interspersing said segments with gaps.
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9. A system for encrypting an input signal, comprising:
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means for filtering said input signal to provide a signal in a first path, having frequency components in a first band, and a signal in a second path having frequency components in a second band which is largely different from said first band; means for shifting the frequency composition in at least one of said paths so that the frequency components in one of the paths lie in a band which substantially overlaps the band occupied by the frequency components of the other path, said means for shifting including means for inverting the frequency composition in at least one of said paths so that frequency components which were at higher frequencies before inversion are at lower frequencies after inversion, and components which were at lower frequencies are at higher frequencies; and means for intermixing time segments of signals from said first and second paths, in a rearranged, randomized time sequence, including means for expanding the frequency composition of the intermixed time segments so that the collection of said intermixed segments exhibits greater bandwidth. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A system for encrypting an analog input signal, comprising:
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means for filtering said input signal to provide a signal in a first path, having frequency components in a higher frequency band, and a signal in a second path having frequency components in a lower frequency band; means for deriving digital samples from the signal in the first path at a first rate and from the signal in the second path at the same rate, and for inverting the frequency composition in said first path so that frequency components which were at higher frequencies before inversion are at lower frequencies after inversion and components which were at lower frequencies are at higher frequencies, and for shifting the higher band frequency components in said first path to lie in said lower band; and means for intermixing segments of the samples from said first and second paths and converting to analog form at a rate greater than twice said first rate to provide a sequence of rearranged, randomized time segments of signals from said first and second paths, including means for interspersing said segments with gaps.
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17. A method of encrypting an input signal, comprising:
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deriving signal segments in digital form, each segment having multiple digitized samples and containing information from said input signal, and intermixing said segments and providing a rearranged output time sequence of said segments in analog form, the rate of said converting being greater than the minimum rate necessary to intermix said segments and convert them to analog form, so that each segment in the output analog sequence retains the information thereof from the input signal, but is separated from the next segment in the sequence by a substantial gap containing no information from the input signal, thereby to reduce the susceptibility of the output time sequence to degradation in transmission.
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18. A system for encrypting an input signal, comprising:
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means for deriving signal segments in digital form, each segment having multiple digitized samples and containing information from said input signal, and means for intermixing said segments and providing a rearranged output time sequence of said segments in analog form, the rate of said converting being greater than the minimum rate necessary to intermix said segments and convert them to analog form, so that each segment in the output analog sequence retains the information thereof from the input signal, but is separated from the next segment in the sequence by a substantial gap containing no information from the input signal, thereby to reduce the susceptibility of the output time sequence to degradation by transmission.
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Specification