From: Bill Sommerfeld <sommerfeld@orchard.medford.ma.us>
Date: Mon, 19 Apr 93 06:37:00 PDT
To: psionic@wam.umd.edu
Subject: Amiga Crypto
In-Reply-To: <199304190250.AA12313@rac3.wam.umd.edu>
Message-ID: <9304191229.AA00116@orchard.medford.ma.us>
MIME-Version: 1.0
Content-Type: text/plain


I think you're off by a factor of 8..

8K samples/sec is 8K bytes/second, not 8Kbits/sec

If we had universal ISDN at 56kb/s or 64kb/s, encrypted voice using
PC-class machines would be trivial.  Instead, we have to compress down
to a data rate comparable to ~1800 8-bit samples/second (V.32bis
speed; modem compression won't do very much -- unless nobody's talking
-- as voice samples do *not* compress effectively using compression
algorithms optimized for ASCII text).  While fiddling with my
SoundBlaster and some dialogue sampled from a T.V.  program last
night, it became clear to me that cutting back to ~4K 4-bit
samples/second isn't quite good enough, and the compression in either
UNIX compress or PGP isn't really tuned for audio samples.

It's not the crypto that's the limiting factor, it's the compression.

That's why the CELP technology that Phil Karn and John Gilmore are
talking about is so important..

					- Bill