From: Jason Asbahr
I don't remember hearing this exact use of privacy-enhanced voice
communication discussed on the list before, but I might not have been
paying attention. :-)
I started asking about this recently and discovered that a lot of people
are interested in it and some of them are even doing something about it.
The most promising group is an Internet Engineering Task Force working
on a project called 'nevot' (network voice terminal) - I'll include the
readme after this post. It's only drawback is that it doesn't handle
completely-software low baud rates that'll work over the internet *on top
of* v32bis modems running slip or ppp. I'm working with some folks to
hack up a really low bandwidth scheme and when our experiments are
successful (if...) we'll feed them back to these folks so that everyone
can use it.
If anyone here is working on low bandwidth digital voice, there's a
mailing list on netphone{-request}@moink.nmsu.edu - its a low-volume
list and really only for reporting what people are working on; chatty
discussions would probably be better on comp.speech or sci.crypt.
Remember that before we get crypto voice, we need non-crypto voice, so
there's no real reason to discuss the basics in a crypto group.
What do you think about encrypting voice communication in a
non-real-time sense? Say I record a message (8-bit CODEC) on my NeXT
or on a friend's PC Soundblaster and then encrypt/scramble the file in
such a way that the resultant file is still audible. I can then leave
that message on the recipient's answering machine or voice mail box
for him to later record and decrypt on his computer. This method would
make private voice communication more accessable, as it doesn't require
real-time levels of performance.
This is baically what the multi-media extentions to email are about - check
up on MIME if you don't know about it. Email mechanisms are fine - the
concept of a 'software answering machine' is seductive, but we don't need
anything special when you can say 'mail -voice fred' and pick up a mike and
talk into it...
Graham.
---------------
See also gaia.cs.umass.edu:~ftp/pub/nevot/*
NEVOT - A network voice terminal (BETA RELEASE 1.3 03/25/93)
(c) Henning Schulzrinne
=============================================================
NOTE: The .nevotinit files from versions prior to 1.3 are incompatible
with the current command language and should be deleted.
DESCRIPTION:
The network voice terminal (NEVOT) allows audio-capable workstations to
participate in audio conferences across local and wide area networks.
Features:
- real-time protocols:
- NVP (network voice protocol), as used by 'vat' (LBL) and VT (isi)
- 'vat' native packet format and session protocol
- RTP draft
- versions for:
- Sun SPARCstation (SunOS 4.1.x and Solaris 5.x)
- SGI Indigo (4D Series) and
- Personal DECstations [as soon as we can get the DEC audio library to work]
- GUIs:
- XView
- Tk [in progress]
- curses
- dumb terminal
- fully controllable by Tcl-based command language
- can serve as gateway for protocol and encoding translation
- network transport protocols:
- TCP
- unicast/multicast UDP
- ST-II [currently inoperative]
- several independent concurrent conferences, each with different
encoding and compression
- DES-based voice encryption (U.S. only)
- audio encodings:
- 64 kb/s (mu-law PCM)
- 32 kb/s G.721 ADPCM (Sun only)
- 32 kb/s Intel DVI
- 24 kb/s G.723 APDCM (Sun only)
- 13 kb/s GSM
- 4.8 kb/s LPC codec
- each site can use different audio encodings
- playback and recording of AIFC and .snd audio files
- extensive statistics and tracing facilities
- arbitrary voice packet length, which may differ for each site
- lost packet and silence substitution
- setable audio buffer occupancy
- configurable adjustment mechanisms for playout delay, VU meter,
silence detector and automatic gain control
- redefinable session identifier string with variable substitution
DOCUMENTATION:
A compressed PostScript file describing Nevot is available for anonymous
ftp from gaia.cs.umass.edu, as file ~ftp/pub/nevot.ps.Z.
INSTALLATION:
The sources are available by anonymous ftp from gaia.cs.umass.edu, as
file ~ftp/pub/nevot/nevot.tar.Z (compressed tar file). The platform-
specific external libraries are contained in the directory
pub/nevot/lib.$ARCH. These typically change rarely. ARCH can be either
dec, sgi, or sun4.
Precompiled binaries are available as well:
nevot/bin.$ARCH/nevot.tar.Z
For the precompiled binaries, you also need to retrieve the
initialization file ~ftp/pub/nevot/nevotinit and rename it to .nevotinit
in the directory from which you plan to start Nevot.
Unpack the compressed tar files, then execute the shell script
compile
You may have to adjust parameters within the shell script to your
local needs, e.g., the compiler name. You also have to install the
tcl library (version 6.7 or later), either the binary version as
mentioned above, or from sources to be found in
sprite.berkeley.edu:tcl. In order to use the UDP multicast and/or
ST-II facilities, you have to install the appropriate kernel
modifications.
Due to export restrictions, the DES encryption code is available only by
e-mail from the author. If you do have the DES code, change the value of
the symbol DES in the Makefiles to 1.
To enable on-line help for the OpenWindows version, the environment
variable HELPPATH should be set to include the source directory where
the .info files are located (here, assumed to be
/usr/local/nevot/xview):
setenv HELPPATH ${HELPPATH}:/usr/local/nevot/xview
OPERATION WITH SD:
------------------
sd is a session directory written by Van Jacobson, LBL, available for
anonymous ftp at ftp.ee.lbl.gov.
The nevot/sd directory contains a replacement for the sd start_audio
procedure, which you can insert into your ~/.sd.tcl startup file. Make
sure that the directory containing the Nevot binary is in your path.
Use at your own risk (i.e., don't blame VJ if it doesn't work...).
DIFFICULTIES:
-------------
If you experience difficulties, check the problems.tex file in the
doc directory.
BUG REPORTS:
This is a beta release. Please send all bug reports and suggestions
to the author at hgschulz@cs.umass.edu. New releases will be
announced through the rem-conf mailing list (to join the list, send a
request to rem-conf-request@es.net). I would appreciate if you could
let me know how you are using the software.
[A version for the Personal DECstation and DECstations with the DEC audio
hardware is currently under development.]
COPYRIGHT:
All sources and documentation (except those listed in the
acknowledgements or otherwise identified) are (c) Henning Schulzrinne
1992, University of Massachusetts and AT&T Bell Laboratories. Do not
redistribute this software, or integrate with other software, without
preserving the copyright notice. All changes have to be clearly
marked. You may modify the code as long as you provide me with a
copy.
ACKNOWLEDGEMENTS:
The DES encryption module was developed by Steve Kent and John Linn of
BBN Communications Corporation, Cambridge, MA and provided by Karen Seo
of BBN. The audio library incorporating G.721 and G.723 audio
compression was provided by Daniel Steinberg of Sun Microsystems. It may
at some point be integrated into the regular Sun OS. The Intel/DVI ADPCM
codec was slightly modified from sources by Jack Kansen (CWI) and is
copyrighted 1992 by Stichting Mathematisch Centrum, Amsterdam, The
Netherlands (used by permission).
The ST-II API and kernel support was developed by Charlie Lynn at BBN.
The ST-II API (\C{st2_api.h}) is copyrighted (c) 1991 by BBN Systems and
Technologies, a division of Bolt Beranek and Newman, Inc. and used by
permission. The UDP multicast kernel support was written by Steve
Deering, Xerox Parc. Charlie Lynn (BBN) was helpful with some of the
fine points of the ST-II API.
The Tcl interpreter was developed by John Osterhout, University of
California at Berkeley. The sources are copyright University of
California and used by permission.
Advice on porting \nevot\ to the Silicon Graphics platform and
numerous bug fixes were provided by Andrew Cherenson (SGI). Michael
Halle (MIT) figured out how to get Xview applications to display fonts
at the design sizes. The VU meter is based on discussions with Gints
Klimanis (SGI).
The audio mixing (mix.c) and checksum code (checksum.c) was taken from
the ISI voice terminal (VT), copyright June 1991 by the University of
Southern California, by permission. The silence detector and the ST-II
code are modified versions of the respective parts of VT.
The \vat\ session and audio protocol were implemented based on
descriptions provided by Van Jacobsen.
The I/O flags interpreter (flags.c) is a modified version of software
contributed to Berkeley by Chris Torek. Copyright (c) 1990 by the
Regents of the University of California; used by permission.
