An asynchronous telephone speech scrambler with a new key generation method

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.

Name thesis:degree_name

Master of Applied Science - MASc

Level thesis:degree_level

master's

Discipline thesis:degree_discipline

Electrical and Computer Engineering

Grantor dc:publisher

University of British Columbia

Year dc:date

1993

Author dc:creator

• Woo, Raymond W. M.

Statement dc: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.

Language dc:language

eng

Handle dc:identifier

http://hdl.handle.net/2429/1544

OAI identifier oai:identifier

oai:circle.library.ubc.ca:2429/1544