Open Source Windows SSH Client Delivers Security Boost

Monday Sep 13th 2010 by Juliet Kemp

The Windows SSH client, PuTTY, is incredibly useful and becomes even more so when set up with a private/public keypair.

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The Windows SSH client PuTTY is incredibly useful; even more useful is setting it up with a private/public keypair.

First, use PuTTYgen (available from the download page) to generate a new keypair. Specify a password, and save both parts of the keypair. Paste the public part (shown in the Puttygen window) into the ~/.ssh/authorized_keys file on your remote host, and save the file.

Now, open the PuTTY configuration window; load the config for your remote host (create and save it if necessary). Go to the Auth submenu (under Connection-SSH), and specify the private key in the box at the bottom. When you connect, you should now be challenged for your key passphrase rather than for your regular password.

You can also use Pageant to manage the key. Launch Pageant, and an icon will appear in the system tray. Right-click on this to add a new key, then provide the location for your private key, followed by your passphrase. You can now log in to your remote host via PuTTY (and, perhaps more usefully, PSCP and other PuTTY-related programs) without having to give the key again.

To make this even easier, set Pageant to run at startup. On Windows 7, locate the Startup folder by clicking the Start menu and clicking All Programs. Right-click the Startup menu, and choose Explore (to launch for this user only). Create a shortcut for Pageant, then dump it in the Startup menu. To specify which key you want to load, right-click the shortcut and choose Properties, then add the location of the key to the end of the Target field:

C:pageant.exe C:Usersjulietkeysthathost_key.ppk

(A note: I found Pageant couldn't locate a key stored on a network drive; the key must be on a local drive.) Next time you log on, you'll be challenged for your remote host key. Thereafter, you can log in password-free.

Juliet Kemp has been messing around with Linux systems, for financial reward and otherwise, for about a decade. She is also the author of "Linux System Administration Recipes: A Problem-Solution Approach" (Apress, 2009).

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