Changing the passphrase of a puttygen private key in Windows

Solution 1:

Check this out:

Putty does not store keys in an OpenSSH-compatible format. You need to use the "puttygen" tool to manipulate your private key.

(via this document, via Google):

To change or set a passphrase on an SSH key under PuTTY, do the following:

Run the puttygen.exe program. Click on the "Load" button. Select the private key file that you want to put a passphrase on. Enter the new desired passphrase in the "Key passphrase" and "Confirm Passphrase" fields. Click on the "Save private key" button. Overwrite the existing copy of your key.

From:

https://superuser.com/questions/522159/unable-to-change-password-for-private-ssh-key

Solution 2:

puttygen on Windows doesn't seem to accept any command line arguments that I can tell. That error is complaining about not being able to find the -P key I believe. If you run puttygen.exe key.ppk instead that should load the ppk into puttygen and allow you to give it a new passphrase and then re-save your key.