virtual private network (VPN) based on the internet instead of leased lines offer organizations of all sizes the promise of low-cost, secure electronic network. By explaining how VPNs actually work, networking expert Jon Snader shows software engineers and network administrators how to use tunneling, authentication, and encryption to create safe, effective VPNs for the environment. Special topics covered include: Block and stream symmetric ciphers such as AES and RC4, and asymmetric, such as RSA and password authentication code EIGamalMessage, including HMACsTunneling gtunnelSSL technology based protocol for building network-to-network protocol VPNsSSH as drop-in replacement for telnet, ftp, and the BSD r- commandsLightweight VPN, including VTun, CIPE, tinc, and OpenVPNIPsec, including its protocols Authentication Header (AH), Encapsulating Security Payload (ESP), and IKE (the key management protocol) Packed with details, the text can be used as a handbook explaining the function of the protocol and message format they use.