“Linux FreeS/WAN is an implementation of IPSEC & IKE for
Linux.”
“IPSEC is Internet Protocol SECurity. It uses strong
cryptography to provide both authentication and encryption
services. Authentication ensures that packets are from the right
sender and have not been altered in transit. Encryption prevents
unauthorised reading of packet contents.
“These services allow you to build secure tunnels through
untrusted networks.”