Secure shell (SSH) was designed as an alternative to some of the insecure protocols and allows users to securely access resources on remote computers over an encrypted tunnel. The Secure Shell Protocol (SSH) is a protocol for secure remote login and other secure network services over an insecure network. The SSH authentication protocol runs on top of the SSH transport layer protocol and provides a single authenticated tunnel for the SSH connection protocol.
SSH’s services include remote log-on, file transfer, and command execution. It also supports port forwarding, which redirects other protocols through an encrypted SSH tunnel. Many users protect less secure traffic of protocols, such as X Windows and VNC (virtual network computing), by forwarding them through a SSH tunnel.
The SSH tunnel protects the integrity of communication, preventing session hijacking and other man-in-the-middle attacks. Another advantage of SSH over its predecessors is that it supports strong authentication. There are several alternatives for SSH clients to authenticate to a SSH server, including passwords and digital certificates.
Keep in mind that authenticating with a password is still a significant improvement over the other protocols because the password is transmitted encrypted.
There are two incompatible versions of the protocol, SSH-1 and SSH-2, though many servers support both. SSH-2 has improved integrity checks (SSH-1 is vulnerable to an insertion attack due to weak CRC-32 integrity checking) and supports local extensions and additional types of digital certificates such as Open PGP. SSH was originally designed for UNIX, but there are now implementations for other operating systems, including Windows, Macintosh, and OpenVMS.
Is SSH 3.0 the same as SSH3?
The short answer is: NO SSH 3.0 refers to version 3 of SSH Communications SSH2 protocol implementation and it could also refer to OpenSSH Version 3.0 of its SSH2 software. The "3" refers to the software release version not the protocol version. As of this writing (July 2013), there is no SSH3 protocol.
"Server authentication" is incorrect. Though many SSH clients allow pre-caching of server/host keys, this is a minimal form of server/host authentication.
"Host authentication" is incorrect. Though many SSH clients allow pre-caching of server/host keys, this is a minimal form of server/host authentication.
"Guest authentication" is incorrect. The general idea of "guest" is that it is unauthenticated access.
Reference(s) used for this question:
http://www.ietf.org/rfc/rfc4252.txt
Hernandez CISSP, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third Edition ((ISC)2 Press) (Kindle Locations 7080-7088). Auerbach Publications. Kindle Edition.
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