-----BEGIN OPENSSH PRIVATE KEY-----
...

##</code><code>##

$ openssl genrsa -out privatekey

-----BEGIN RSA PRIVATE KEY-----
...

$ chmod 600 privatekey
$ ssh-keygen -y -f privatekey > publickey

##</code><code>##

localhost: Trying pubkey authentication with key file 'privatekey'
localhost: Login completed, opening dummy shell channel.
localhost: channel 0: new [client-session]
localhost: Requesting channel_open for channel 0.