From: "Dave Emery" <die@pig.die.com>
Date: Wed, 16 Aug 95 10:39:46 PDT
To: stewarts@ix.netcom.com (Bill Stewart)
Subject: Re: Purple Boxes
In-Reply-To: <199508160843.BAA25109@ix9.ix.netcom.com>
Message-ID: <9508161739.AA02917@pig.die.com>
MIME-Version: 1.0
Content-Type: text/plain


> 
> At 10:30 PM 8/15/95 -0400, Dave Emery wrote:
> >	I reiterate my suggestion of a few months ago that
> >one could quite easily adapt the firmware on one of the new simultanious
> >data and digital voice on the same phone line modems to incorperate
> >encryption, and quite possibly encryption/key exhange interoperable
> >with some mode of PGPphone.

> Most modems I've seen only have one set of audio interfaces,
> and a bump-in-the-cord phone needs two (one for the voice side,
> one for the modem line side.)  (Having two jacks doesn't count.)
> So you'd need at least two modems, one straight and one re-educated,
> and you'd probably need lots more flash ROM than the average modem has.

	The kind of modem I was refering to is designed to supply a
digital voice connection interleaved with 28.8 kb V.34 high speed data
over a common modem connection.  As such it has an extra audio A/D and
D/A and line interface; in fact some of these modems actually have a
full telco CO type phone line interface so one can plug in a regular
vanilla phone and talk full duplex over the digital path just as on an
analog phone line.  They are already trully bump-in-the-cord devices. 

	These modems are a new product, just being introduced, and are
apparently aimed at the service desk/tech support market where they
supply the capability for someone diagnosing a problem to have the
customer's screen display on their system and access their keyboard
while talking to the customer about what is wrong.   (As a historical
note, I was involved in the development of this technology at
Data General in the late 70's using fdm data over voice analog signalling
- the reason it didn't catch on was that the modem connection was
very slow (300 baud)).

	There is an effort in the modem industry to standardize the
voice compression used and the protocol so such modems will interoperate
with those made by other manufacturers  - I don't think anybody has
addressed encryrption in this protocal (after all, the NSA has kept
encryption out of the data side of modems where it would be trivial
to implement).

	As for the ROM size issue - I'm sure if one was expecting to
be able to drop in PGPphone code relatively unmodified it would
be a problem, but actually implmenting the core encryption and crypto sync
stuff would only be a few tens of kb of code at most in a ROM that
may well be 512 kb or more now with significant space reserved for
expansion and bug fixes and support of older modem protocols.

							Dave Emery
							die@die.com