tcpcrypt - Definition from the Hotspot Shield Glossary
This is an encryption protocol that is used to encrypt data in a network. Tcpcrypt is a stand-alone product that requires no application changes or configuration - It can simply be implemented and used in conjunction with your network.
This protocol uses opportunistic encryption - If the other device in the transmission can understand Tcpcrypt then the data will be encrypted, if not, the data will be sent as clear text as normal. Tcpcrypt removes the need for obtaining PKI’s and means you can encrypt your data in a much easier and quicker manner, furthermore it has high performances up to 25x faster than SSL and is more suited for deployment on a wider scale.