
                        Speak Freely for Unix
                Voice Communication Over Data Networks

                            by John Walker
                    Release 7.1  --  September MIM

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 workstations with digital audio capability, linked
by  a  fast  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 can currently be built for the following systems
(assuming they are equipped with suitable sound hardware):

          System                        Ported By
  =========================== =============================
  SunOS 4.1.x                 John Walker
  Silicon Graphics IRIX 5.3   John Walker
  Solaris 2.4 (SPARC and x86) Hans Werner Strube
  FreeBSD                     Andrey A. Chernov
  Linux                       A host of volunteers
  Hewlett-Packard             Marc Kilian

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 key supplied in a file, DES
Blowfish, and/or IDEA with given key(s).  The DES  implementation  was
developed  by  Phil Karn, KA9Q. The Blowfish encryption module and the
DES encryption library used for encrypting and decrypting VAT and  RTP
protocol packets were developed by Eric Young.  The Blowfish algorithm
was invented by Bruce Schneier and is in the public domain.  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.  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 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 Speak Freely  for  Unix  are  given  in  the
manual  pages.   You can view the manual pages on your screen with the
command:

    make manpage

To build the program, edit  the  Makefile  and  set  the  #defines  as
appropriate  for your system and preferences, then make.  If the build
is successful, the executables for all the Speak Freely programs  will
be in the build directory.

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
        http://www.fourmilab.ch/
