Convert a .ppk private key (Putty) to a base64/pem private key for OpenSSH or OpenSSL
How to SSH to AWS EC2 Instance from PuTTY using PEM Key Pair
OpenSSL – How to renew an expired SSL Certificate, so that the new SSL Certificate has the same Public Key as the old Certificate | University of South Wales: Cyber University of
How to install and use puttygen to create new key pairs and change passphrases. Installing keys on server, managing SSH keys.