SSH Reference Manual

SSH Protocol Reference
The SSH Protocol
SSH is a protocol for encrypted network traffic and a set of associated programs which have its roots in the Unix domain.
The first version of SSH (SSH version 1 or SSH1) became popular in 1995 and was replaced by an improved version
(SSH version 2 or SSH) in 1997. In 2006, SSH version 2 became a proposed internet standard with the publication of a
group of RFCs by the Internet Engineering Task Force (IETF).
For more information on the SSH protocol we recommend the following reading:
• "Secure Shell" in Wikipedia: http://en.wikipedia.org/wiki/Secure_shell
• A popular commercial SSH implementation for PC and Unix systems comes from a company called SSH. Their
website is http://www.ssh.com
.
• A guide to the generation of SSH key pairs can be found at
http://apps.sourceforge.net/trac/sourceforge/wiki/SSH%20keys
• A comprehensive book on SSH is SSH, The Secure Shell, Daniel J. Barrett, published by O'Reilly
Implementation Overview
Supported Versions
The SSH2 software package only supports version 2 of the SSH implementation.
Cipher Suites
For a list of supported cipher suites and MACing algorithms, please see the parameters "CIPHERS" and "MACS" in
chapter "Configuring and Running SSH2".
Implementation of the SSH protocol
SSH is a complex security protocol involving many sophisticated algorithms, therefore implementing SSH on any
platform is not a trivial task. There are many intricacies in implementing SSH; just the fact that "it works" does not
guarantee the quality of an implementation.
The following code has been used as part of the SSH2 software package:
• a commercial SSH implementation (bitvise sshlib, see http://www.bitvise.com/products.html
) which is based on
the popular crypto library crypto++ (see http://sourceforge.net/projects/cryptopp/).
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