Newsgroups: comp.speech
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From: walter@mprgate.mpr.ca (Michael Walter)
Subject: Re: Speaker verification  (was: Simple speech recognition needed)
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References: <344uqf$bog@noc.tor.hookup.net> <347cfe$gf8@cherokee.advtech.uswest.com> <1994Sep4.081026.94@ark.franken.de>
Date: Tue, 6 Sep 1994 10:17:39

>From: ralf@ark.franken.de (Ralf W. Stephan)
>Curtis Knittle writes:
>> Greg...what you may really be after is a speaker verification 
>> system.  I don't think you want a system to just recognize the 
>> digits, because then anyone standing around would hear 
>> someone elses PIN, and therefore have access to the area.  

>But then, someone could record your voice --- and not only when
>you say the PIN.  Though this is less likely, it will be a problem.
>Now the question:  Is it possible to decide if a certain voice
>input comes from a recording, or is synthesized using parameters
>that mimick the original speaker?

>ralf

I've read in an article (I believe in CardTech/SecurTech Conference 
Proceedings 1994 from the Biometric Authentication Consortium, Ronald 
Benincasa, DoD) that an individual can NOT say a given word or sequence 
of words the exact same way twice so there is always some randomness involved 
and speaker recognition systems can take this into account. Therefore if 
the spoken PIN or password is exact to the stored voiceprint then it's 
possibly a recording. The system can request another try which if exact to the 
first one will definitely be a recording.
Additionally the system can ask the user to repeat a randomly selected word to 
repeat and check the characteristics of the voice for verification.

Michael Walter  (walter@mprgate.mpr.ca)
MPR Teltech Ltd.
Burnaby, BC  Canada
