librsaref.so is a demonstration dynamic engine that does RSA operations using the old RSAref 2.0 implementation. To make proper use of this engine, you must download RSAref 2.0 (search the web for rsaref.tar.Z for example) and unpack it in this directory, so you'll end up having the subdirectories "install" and "source" among others. To build, do the following: make This will list a number of available targets to choose from. Most of them are architecture-specific. The exception is "gnu" which is to be used on systems where GNU ld and gcc have been installed in such a way that gcc uses GNU ld to link together programs and shared libraries. The make file assumes you use gcc. To change that, just reassign CC: make CC=cc The result is librsaref.so, which you can copy to any place you wish.