From: wcs@anchor.ho.att.com (Bill_Stewart(HOY002)1305)
Date: Tue, 9 Feb 93 17:10:58 PST
To: cypherpunks
Subject: Re: CELP speech compression code at cygnus.com:/pub/celp.speech.tar.Z
Message-ID: <9302100110.AA09266@toad.com>
MIME-Version: 1.0
Content-Type: text/plain


Forwarded for Bill Stewart, who I assume wanted it posted.

Eric
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John, Perry, and others have been commenting on the use of CELP voice compression
and crypto with V.32 or better modems to give end-to-end encrypted speech.
Perry says:
> Fast enough software compression of voice would mean any PC 
> with a DSP card and a V.32 modem could become an unbreakable scrambler.
> The chief problem is that the DSP needed to do decent compression is
> very crunchy, and encryption also tends to be crunchy, so there aren't
> typically enough cycles on your average PC. Of course, were someone to
> commercially market a board that did all this in hardware...

(Please excuse any shameless references to my employer's fine hardware products :-);
I do science fiction, er, um, systems engineering, not hardware...
and it's been a while since our chip people were in my building.)

It may not all be packaged on a single board, but it shouldn't be real tough.
PC and Mac Boards with AT&T DSP32C chips were out several years ago,
which provided something like 25 MFLOPS, which was more than enough
to do voice compression and have leftover guts for crypto
(or use your 386; DES at 9600 baud shouldn't cause much heartburn.)
I assume that by now there are reasonably-priced floating-point DSP boards
from several different vendors out, and AT&T makes modem chipsets and
supporting A/D and fixed-point DSP integer-crunchers.
If CELP can be done in integers, I'd guess you could chain together a
couple DSPs and put together a board for ~$100-150 parts-cost.

Also, how much can you do with the various SoundBlaster-related boards?

			Bill