How to use SSH keys with PuTTY

This article describes how to use PuTTY for passwordless SSH access via public/private key pairs.

Click on Generate to start generating a public/private key pair
You are asked to generate some randomness by moving the mouse on the area below the progress bar:

Optionally you can enter a passphrase to protect your private key, please do so!
Click on "Save private key":

Enter a name and select a destination folder, then click "Save". IMPORTANT: This file MUST reside on your computer and it cannot leave it or be sent over any network.
Do likewise for the public key (click on "Save public key").
Now go back to the PuTTYgen main screen and select the public key with the mouse, right click on the selection and copy it.
Open a new PuTTY session to the Linux machine you want to connect via those SSH keys.
At prompt, cd to .ssh/ folder:

With a text editor of your choice, open the authorized_keys file. If not existing, an empty one will be created:

Go to the end of file and paste the public key as a new line (middle or right mouse buttons click when in text editing mode):

Save, exit and close the PuTTY session. Now you need to tell PuTTY to use the new key pair.
Go back to the PuTTY main window, load your saved session settings from the Session tab.
Go to Connection -> SSH -> Auth and click on "Browse":

Select the private key file you saved previously and click "OK".
Go back to the Session screen, and save the new session settings for future use.
You are done! Try to connect: you should go straight to the shell prompt with no password request.

Possible issues

If you are still prompted for a password, try the following:

Make sure you did not miss any character in the copy/paste of the public key. If not sure, copy it again from the saved public key file and re-do the paste.
Check the authorized_keys permissions if creating a new file. They must be 644 (see the chmod man page).
Make sure your private key is loaded into the PuTTY session.

Topic attachments
I	Attachment	History	Action	Size	Date	Who
png	PuTTYgen1.png	r1	manage	29.9 K	2014-07-11 - 11:41	FedericoMelaccio
png	PuTTYgen2.png	r1	manage	33.5 K	2014-07-11 - 11:42	FedericoMelaccio
png	PuTTYgen3.png	r1	manage	40.1 K	2014-07-11 - 11:42	FedericoMelaccio
png	PuTTYgen4.png	r1	manage	41.9 K	2014-07-11 - 11:42	FedericoMelaccio
png	PuTTYgen5.png	r1	manage	100.8 K	2014-07-11 - 11:42	FedericoMelaccio
png	PuTTYgen6.png	r1	manage	35.6 K	2014-07-11 - 11:42	FedericoMelaccio
png	authkey1.png	r1	manage	45.9 K	2014-07-11 - 11:42	FedericoMelaccio
png	authkey2.png	r1	manage	49.6 K	2014-07-11 - 11:42	FedericoMelaccio
png	authkey3.png	r1	manage	40.3 K	2014-07-11 - 11:42	FedericoMelaccio

Topic revision: r3 - 2016-04-19 - ChrisBrew