SSH FAQ

Q: What is ssh?
A: Ssh (Secure Shell) is a program to log into another computer over a network, to execute commands in a remote machine, and to move files from one machine to another. It provides strong authentication and secure communications over unsecured channels. It is intended as a replacement for rlogin, rsh, and rcp. Additionally, ssh provides secure X connections and secure forwarding of arbitrary TCP connections.

Q: Why should I use it?
A: The traditional BSD 'r' - commands (rsh, rlogin, rcp) are vulnerable to different kinds of attacks. Somebody who has root access to machines on the network, or physical access to the wire, can gain unauthorized access to systems in a variety of ways. It is also possible for such a person to log all the traffic to and from your system, including passwords (which ssh never sends in the clear).

Q: How does it work?
A: All communications are encrypted using IDEA or one of several other ciphers (three-key triple-DES, DES, RC4-128, TSS, Blowfish). Encryption keys are exchanged using RSA, and data used in the key exchange is destroyed every hour (keys are not saved anywhere). Every host has an RSA key which is used to authenticate the host when RSA host authentication is used. Encryption is used to protect against IP-spoofing; public key authentication is used to protect against DNS and routing spoofing.