
                        Speak Freely for Unix
                Voice Communication Over Data Networks

                            by John Walker
                 Release 5.2  --  20th September 1995

The  phone  company  never gives you a break!  You pay a fortune for a
leased line connection to the Internet, and you *still*  have  to  pay
every  time  you  want  to chat with somebody, even though you're both
sitting in front of Sun SPARCStations  or  Silicon  Graphics  machines
with  digital  audio  capability,  linked by a high-bandwidth network.
Speak Freely for Unix  can  intercommunicate  with  Speak  Freely  for
Windows, available from my Web site listed at the end.

Speak Freely for Unix uses the workstation audio hardware and  network
to   allow   bidirectional   conversations  right  over  the  network.
Workstations on local area networks  can  generally  communicate  with
excellent  audio  quality  and  response.   A  software implementation
(developed  by  Jutta  Degener   and   Carsten   Bormann,   Technische
Universitaet  Berlin) of the compression algorithm used in GSM digital
cellular telephones allows operation over  Internet  links  of  modest
bandwidth.   By  using  GSM  compression  in  conjunction  with sample
interpolation, the data rate can be reduced to about 9600 baud.  Users
with  CPUs  too  slow or two heavily loaded to perform GSM compression
and decompression in real time may select less compact but quicker  to
execute ADPCM coding, using an implementation developed by Jack Jansen
of the Centre for Mathematics and  Computer  Science,  Amsterdam,  The
Netherlands.

Sound  can be encrypted either with a one-time pad supplied in a file,
DES and/or  IDEA  with  given  key(s).   The  DES  implementation  was
developed  by  Phil  Karn,  KA9Q.  The IDEA algorithm was developed by
Xuejia Lai and James L. Massey, of  ETH  Zurich.   The  implementation
used in Speak Freely for Unix was modified and derived from original C
code developed by Xuejia Lai and optimized for speed  by  Colin  Plumb
<colin@nsq.gts.org>.    The  IDEA[tm]  block  cipher  is  patented  by
Ascom-Tech AG. The Swiss patent number is PCT/CH91/00117, the European
patent  number  is  EP  0  482  154  B1, and the U.S. patent number is
US005214703.  IDEA[tm] is a trademark of Ascom-Tech AG.  There  is  no
license  fee  required  for  noncommercial  use.  Commercial users may
obtain licensing details  from  Dr.   Dieter  Profos,  Ascom-Tech  AG,
Solothurn  Lab,  Postfach 151, CH-4502 Solothurn, Switzerland, Tel +41
65 242 885, Fax +41 65 235 761.

The  Silicon  Graphics  audio drivers are based on the stand-alone SGI
Netfone  developed  by  Paul  Schurman  (schurman@frs.fi)  of   Espoo,
Finland.

Key generation for IDEA and DES encryption uses an  implementation  of
MD5  message-digest algorithm based on a public domain version written
by Colin Plumb in 1993.  The algorithm is due to Ron Rivest.

Complete instructions for building, installing, and using Speak Freely
for  Unix are given in the manual page, speakfree.1.  You can view the
manual page on your screen with the command:

    make manpage

All files in the speakfree root directory are in  the  public  domain:
"Do  what  thou  wilt  shall be the whole of the law".  I'd appreciate
receiving any bug fixes and/or enhancements, which I'll incorporate in
future versions of the program.  Please leave the original attribution
information  intact  so  that  credit  and  blame  may   be   properly
apportioned.

Please see the readme and/or copyright files in the adpcm,  des,  gsm,
and idea subdirectories for information regarding the distribution and
conditions of use of those components.

AUTHOR
        John Walker
        E-mail: kelvin@fourmilab.ch
        WWW:    http://www.fourmilab.ch/
