Openswan is a free implementation of IPSEC & IKE for Linux, a fork of the
FreeS/WAN project.

IPSEC is Internet Protocol Security and uses strong cryptography to
provide both authentication and encryption services. These services
allow you to build secure tunnels through untrusted networks.
Everything passing through the untrusted net is encrypted by the ipsec
gateway machine and decrypted by the gateway at the other end of the
tunnel. The resulting tunnel is a virtual private network or VPN.

This package contains the daemons and userland tools for setting up
Openswan on a kernel with either the 2.6 native IPsec code, or
FreeS/WAN's KLIPS.