IPSEC

IPSec stands for IP Security, a set of protocols that supports IP layer secure packet exchange. IPsec is expected to be used widely to implement Virtual Private Networks (VPNs). IPsec supports the Transport and Tunnel encryption modes. Transport mode leaves the header untouched, but encrypts the data portion of each packet. Tunnel mode is the more secure encryption method, it encrypts both the header and the data portion. For IPsec to work, the sending and receiving devices must share a public key. This is accomplished through a protocol known as Internet Security Association and Key Management Protocol/Oakley (ISAKMP/Oakley), which allows the receiver to obtain a public key and authenticate the sender using digital certificates.