From: David Neal <dneal@usis.com>
Date: Fri, 11 Aug 95 15:09:17 PDT
To: "Vladimir Z. Nuri" <vznuri@netcom.com>
Subject: Re: PRZ encrypted voice software release imminent
In-Reply-To: <199508111759.KAA05515@netcom8.netcom.com>
Message-ID: <Pine.BSI.3.91.950811164809.28774C-100000@usis.com>
MIME-Version: 1.0
Content-Type: text/plain


On Fri, 11 Aug 1995, Vladimir Z. Nuri wrote:

> 
> when someone invents cheap hardware that you can just plug
> on top of any existing phone, i.e. "the phone adaptor", TPA?,
> *that's* when the world is going to go crazy with crypto.

It's closer than you think.  I've been messing with TI's 
Digital Signal Processing DSK.  For $99 you get a DSP
with audio in, audio out and 10k of memory.  Reference
implementations of : DTMF encoders/decoders; 300, 1200, 2400 baud
modem programs; and voice processing software already exist.

The TI Linear Products Transmission, Switching, Subscriber,
and Transient Suppressors Data Book is sitting on my desk
along with the Data Transmission and Control Circuits (etc)
Data Book.  Combined with the pinouts and software that
came with DSP DSK I've been painfully trying to piece
together how one might glue up a telephone interface.

Unfortunately, I'm a software guy and am still learning.

In any case, assuming Joe STUD Hardware Guy was willing
to make a daughterboard with a 64k memory module (10k is
just not enough) with an FCC approved telephone interface
(available from parts suppliers).  You could have a 25 MIPS
based personal STU.  I'm envisioning a 'black box' with
two RJ-11 jacks which daisy chained in with your phone
like a modern modem.  Triggering key exchange could be
a simple DTMF sequence.  

Ultimately, the device could be combined into a single
board eliminating parts, reducing space, and lowering
power supply requirments.  The DSP DSK currently needs
~14 Volts AC.   I'd like to see that black box
portable and able to use some nine volt or AA batteries.



> all this stuff that requires lots of hardware can be used,
> but the thing that will cause *everyone* to use it is when
> someone invents a TPA. I'm very, very surprised that no 
> one has tried to do this yet.
> 

In any case, I'm trying to do it, but my efforts will never
realise a commericial result.  I just don't have the money
to buy parts in bulk, and without doing that units would be
$200-$500 each.