Supports IPSec (ESP) with Mode Configuration and Xauth.  Supports 
only shared-secret IPSec authentication with Xauth,
AES (256, 192, 128), 3DES, 1DES, MD5, SHA1,
DH1/2/5 and IP tunneling.

Homepage:  http://www.unix-ag.uni-kl.de/~massar/vpnc/

This packages requires libgpg-error and libgcrypt which can be
obtained at slackbuilds.org.  Make sure to install them
in the order listed above.  Libgcrypt won't compile without 
libgpg-error.