
			Speak Freely for Unix
		Voice Communication Over Data Networks

			    by John Walker
		   Release 6.1b  --  August 1996

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

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
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.   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
	WWW:	http://www.fourmilab.ch/
