There is a perl 5 sha1.pl which you can rename to sha1 and put somewhere in
your path if you can't compile the C code for some reason.  Only short
strings are sha1'd by the eternity server, so it shouldn't affect
performance greatly.

Laszlo Vecsey <master@internexus.net> contributed a make file, so you should
be able to just type make; make install (check you like the INSTALLPATH in
the Makefile: /usr/bin).

If you don't get on with the make file, the compile script is still here
with "source compiling" or ". compiling" depending on your shell.

In either case (compiled or sha1.pl) put the full path to your sha1 in 
eternity.conf
