Making it easier to work with PuTTY keys and OpenSSL PEM keys

I have a load of Linux logins, which I access using PuTTY from Windows. Exporting a PuTTY public/private key as an OpenSSH PEM is familiar territory.

Here's a recipe I used for getting an SSH-style public key from a PEM format private key, which I export from PuTTY:

http://webjob.sourceforge.net/Files/R...

It looks healthy enough, but doesn't generate a comment and that seems to choke SftpDrive, causing it to complain about the public key format. I manually added a comment, which SftpDrive approved of, but it then reckoned that the public key did not match my PEM private key.

When would make life easier, if if SftpDrive accepted the PEM public and private keys, and we could take ssh-keygen out of the mix.

So far the only key pair I've managed to use with SftpDrive so far is the pair generated by SftpDrive itself, but I want to avoid having to add another public key to ~/.ssh/authorized_keys2 if I can avoid it.