If you want to use GnuTLS (below) for TLS and SSL support, you will first need to install libgcrypt. If you cannot load libgcrypt and its development package from RPMs via your OS package installer (or if the version of libgcrypt that it installs is not new enough for GnuTLS liking), download the tar file from ftp://ftp.gnupg.org/gcrypt/libgcrypt and untar it in the top level source directory (e.g. /rpm/Apache):
tar -xvzf libgcrypt-a.b.yy.tar.gz
It will create a new directory for that version of libgcrypt. Switch to that directory and build libgcrypt:
cd libgcrypt-a.b.yy
./configure --prefix=/usr/local
make
Since it is likely that the package manager of your OS will have installed a version of libgcrypt that is being used by other stuff in the system, we have chosen to install the new version that we build in /usr/local (hence the need for "--prefix"). However, in many versions of the libgcrypt configure script, the default installation location is /usr/local so you may not need to specify this parameter.
Switch to super-duper user and install libgcrypt:
su
make install