• Internet Protocol Security (IPSec): IPSec is used for authenticity of two communicating hosts not users. Mostly used for building VPN and connecting a remote machine.
  • Secure Socket Layer/Transport Layer Security (SSL/TLS): SSL/TLS works over TCP and tunnels other protocols using TCP, adding encryption and authentication of the server and optional authentication of client. SSL is in the process to be taken over by TLS.
  • OpenPGP and S/MIME: Two competing incompatible standards for securing email.
  • SSH: Used for securing remote terminals over internet
  • Kerboes: Used for single sign-on and authenticates users against a central authentication and key distribution server