Eric go ahead; Cpunks start Cpunking again

Good grief! At >500 k, this is the longest 10% thread (SNR 1:10) I've seen 
in ages. Eric please go ahead and add the X-Bozo: header field, we can do
another in-depth study on its effects in 3 months, while Tim, you, and I 
figure out how to make digisigs convenient for ourselves.

(After all, Eric might not own the 'Cypherpunks list' whatever that is, but
he does own cypherpunks@toad.com; we could all move elsewhere, except that
despite a few crashes I've found this one especially reliable.)

In the meanwhile, could we get back to cryptography? There are so many 
interesting things happening out there - good earnest tough-on-crime
Congressmen waiting to sign HR 5199 (the Clipper Bill); the DigiCash trial;
the great voice-over-data protocols and products introduced by Intel, Rockwell,
ZyXEL and others at Comdex which will make Voice-PGP so much easier (ZyXEL
2864 does V.34 28.8kbps, voice, fax/data simultaneously, 230kbps DTE, parallel
port to print faxes on printer when computer is off, $350).

Now what _I_ want is some way to integrate PGP with Netscape... 

Rishab

ObEconomistPlug: British judges ruled against a Liberal Democrat Party request 
to re-run elections where the "Literal Democrats" won 10,000 votes. The new
Conversatives will target Tory seats next year. How about a good Cypherpunk
Senator ... from the Rebuplican party?

-----------------------------------------------------------------------------
Rishab Aiyer Ghosh             "Clean the air! clean the sky! wash the wind!
rishab@dxm.ernet.in                   take stone from stone and wash them..."
rishab@arbornet.org
Voice/Fax/Data +91 11 6853410  
Voicemail +91 11 3760335                 H 34C Saket, New Delhi 110017, INDIA

On Fri, 2 Dec 1994 rishab@dxm.ernet.in wrote:

> 
> In the meanwhile, could we get back to cryptography? There are so many 
> interesting things happening out there - good earnest tough-on-crime
> Congressmen waiting to sign HR 5199 (the Clipper Bill); the DigiCash trial;

DigiCash trial?  Tell me more!

> the great voice-over-data protocols and products introduced by Intel, Rockwell,
> ZyXEL and others at Comdex which will make Voice-PGP so much easier (ZyXEL
> 2864 does V.34 28.8kbps, voice, fax/data simultaneously, 230kbps DTE, parallel
> port to print faxes on printer when computer is off, $350).

Now THAT sounds cool!  :)  Wonder how long it will be before someone uses 
PGP in a phone :)  How much processing power would it take to do that on 
the fly anyway?

> 
> Now what _I_ want is some way to integrate PGP with Netscape... 

What's Netscape?

--------------------------------------------------------------------------
| Geoffrey@crl.com                The opinions expressed herein may or   |
| Geoffrey Faivre-Malloy          may not be the opinions of my employer.|
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the great voice-over-data protocols and products introduced by
   Intel, Rockwell, ZyXEL and others at Comdex which will make
   Voice-PGP so much easier

As I understand these voice-over-data products, the voice goes over
analog, added to the modem signal.  The modem signal is interpreted,
and then reconstructed and subtracted from the incoming signal,
leaving voice.  Very clever, but insufficient for secure phones.

Eric

> 
> 
>    the great voice-over-data protocols and products introduced by
>    Intel, Rockwell, ZyXEL and others at Comdex which will make
>    Voice-PGP so much easier
> 
> As I understand these voice-over-data products, the voice goes over
> analog, added to the modem signal.  The modem signal is interpreted,
> and then reconstructed and subtracted from the incoming signal,
> leaving voice.  Very clever, but insufficient for secure phones.
> 

	I can't quite see how this would work unless the voice was run
at a very low level relative to the data.  In order to subtract the
modulated version data coming from the other end you have to know
exactly what it is, and in order to do that you need sufficient signal
to noise of data over everthing else to reliably demodulate it or you
need some means of reliably predicting it.
	
	  Now I recognize that some of the time there is little or no
entropy in the information in one direction (it is completely
predictable - such as flags during LAPM idle intervals) and it is
possible that one could contruct a syllabic gizmo that would turn off
the entropy in the data when talkspurts happened by doing flow control
and stopping information transmission during periods that speech was
loud.  But all of this seems a bit much, and certainly would be subject
to lots of kinds of degradation depending on the speech content and
any nolinearity in the channel.

	In general the modulations used in modems require at least 12-15 db
of SNR for decent BERs - this would imply that if the line was not
timeshared with voice in talkspurts that the peak level of the voice
would have to be about 20 db below the modem tones.  I guess that this
would still result in intelligible speech even though it would effectively
be transmitted by only a couple of bits per 8 khz sample.

	And yes I guess that by using forward error correction on the
data at a variable coding rate one could allow the voice to creep
up on the data a bit more by using a heavier duty error correction
during talk spurts.

	I had assumed that these products digitized voice and multiplexed
it with the data stream however.   Certainly there are technologies to
do this including variable rate vocoding (ala Qualcomm) that would
allow almost the full bandwidth of the line to be used for data.


	[ And yes I'll bring up premail tommorow so I can sign things if
I can get around to it without interrupting serious work work - but I'm left
wondering who in the hell would want to forge posts from me ? ]

						Dave Emery N1PRE

From: "Dave Emery" <die@pig.die.com>

	   I can't quite see how this would work unless the voice was run
   at a very low level relative to the data.  

I believe there are also maximum rates on the data when used with
voice (4.8 kbps?) and the modulation doesn't use echo cancellation.

With the lower bit rate you can get away with a lot, particularly with
modern DSP's.

Eric