SSH Permission denied (publickey,gssapi-keyex,gssapi-with-mic) when using PuTTYGEN key files.

Using PuTTYgen ssh keys with the OpenSSH ssh command on a linux system fails with Permission denied errors because it uses a different format than OpenSSH keys.

Attempting to use .ppk keys generated using Puttygen to login interactively to a Linux instance via ssh fails with the following errors:

$ ssh -i deployment_key.txt opc@<IP_ADDRESS>

Enter passphrase for key 'deployment_key.txt':

Permission denied (publickey,gssapi-keyex,gssapi-with-mic).

This occurs because Puttygen generated key files use a different format to what the ssh command on a linux system uses.

To fix this issue do the following steps:

1. Download PuTTYgen from