Manual Putty

PuTTY
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PuTTY is a free (MIT-licensed) Win32 Telnet and SSH client. This manual documents PuTTY, and its companion utilities PSCP, PSFTP, Plink, Pageant and PuTTYgen.

_Note to Unix users:_ this manual currently primarily documents the Windows versions of the PuTTY utilities. Some options are therefore mentioned that are absent from the Unix version; the Unix version hasfeatures not described here; and the pterm and command-line puttygen utilities are not described at all. The only Unix-specific documentation that currently exists is the man pages.

Chapter 1: Introduction to PuTTY
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PuTTY is a free SSH, Telnet and Rlogin client for 32-bit Windows systems.

1.1 ¿What are SSH, Telnet and Rlogin?;If you already know what SSH, Telnet and Rlogin are, you can safely skip on to the next section.
SSH, Telnet and Rlogin are three ways of doing the same thing:
logging in to a multi-user computer from another computer, over a network.

Multi-user operating systems, such as Unix and VMS, usually present a command-line interface to the user, much like the `Command Prompt' or`MS-DOS Prompt' in Windows. The system prints a prompt, and you type commands which the system will obey.

Using this type of interface, there is no need for you to be sitting at the same machine you are typing commands to. The commands, and responses, can be sent over a network, so you can sit at one computer and give commands to another one, or even to more than one.

SSH,Telnet and Rlogin are _network protocols_ that allow you to do this. On the computer you sit at, you run a _client_, which makes a network connection to the other computer (the _server_). The network connection carries your keystrokes and commands from the client to the server, and carries the server's responses back to you.
These protocols can also be used for other types ofkeyboard-based interactive session. In particular, there are a lot of bulletin boards, talker systems and MUDs (Multi-User Dungeons) which support access using Telnet. There are even a few that support SSH.
You might want to use SSH, Telnet or Rlogin if:
- you have an account on a Unix or VMS system which you want to be able to access from somewhere else.
- your Internet ServiceProvider provides you with a login account on a web server. (This might also be known as a _shell account_. A _shell_ is the program that runs on the server and interprets your commands for you).
- you want to use a bulletin board system, talker or MUD which can be accessed using Telnet.

You probably do _not_ want to use SSH, Telnet or Rlogin if:
- you only useWindows. Windows computers have their own ways of networking between themselves, and unless you are doing something fairly unusual, you will not need to use any of these remote login protocols.

1.2 ¿How do SSH, Telnet and Rlogin differ?.
This list summarises some of the differences between SSH, Telnet and Rlogin.
- SSH (which stands for `secure shell') is a recently designed,high-security protocol. It uses strong cryptography to protect your connection against eavesdropping, hijacking and other attacks. Telnet and Rlogin are both older protocols offering minimal security.
- SSH and Rlogin both allow you to log in to the server without having to type a password. (Rlogin's method of doing this is insecure, and can allow an attacker to access youraccount on the server. SSH's method is much more secure, and typically breaking the security requires the attacker to have gained access to your actual client machine).
- SSH allows you to connect to the server and automatically send a command, so that the server will run that command and then disconnect. So you can use it in automated processing.
The Internet is a...