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UBC Theses and Dissertations
An asynchronous telephone speech scrambler with a new key generation method Woo, Raymond W. M.
Abstract
The design of an asynchronous telephone speech scrambler is proposed and its performance experimentally studied. The scrambler transforms the speech signal into a scrambled form by permuting the frequency coefficients of the speech signal. These coefficients are permuted in pairs instead of individually. Subjective tests indicate that such an arrangement results in an improvement in descrambled speech quality but no increase in the residual intelligibility of the scrambled speech signal. A new criterion for selecting good scrambling permutations known as the derangement criterion is introduced. Subjective tests based on the number test confirm that keys satisfying this criterion are able to produce scrambled speech with virtually no residual intelligibility. A new derangement generation algorithm is introduced. This algorithm maps an integer g, in the range of 0 ≤ g < (n - 1)!, uniquely to a derangement of n elements.
Item Metadata
Title |
An asynchronous telephone speech scrambler with a new key generation method
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1993
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Description |
The design of an asynchronous telephone speech scrambler is proposed and its performance experimentally studied. The scrambler transforms the speech signal into a scrambled form by permuting the frequency coefficients of the speech signal. These coefficients are permuted in pairs instead of individually. Subjective tests indicate that such an arrangement results in an improvement in descrambled speech quality but no increase in the residual intelligibility of the scrambled speech signal. A new criterion for selecting good scrambling permutations known as the derangement criterion is introduced. Subjective tests based on the number test confirm that keys satisfying this criterion are able to produce scrambled speech with virtually no residual intelligibility. A new derangement generation algorithm is introduced. This algorithm maps an integer g, in the range of 0 ≤ g < (n - 1)!, uniquely to a derangement of n elements.
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Extent |
3911299 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2008-08-27
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0065101
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1993-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.