Inspect DSA/RSA private key

Based on <http://martin.kleppmann.com/2013/05/24/improving-security-of-ssh-private-keys.html>.
Create new RSA SSH key
Use strong RSA key length

Based on a reading of a 2003 article <https://www.rsa.com/rsalabs/node.asp?id=2004> recommending 3072 bits for protection until 2031 and beyond.
Create SSH-compatible encrypted key pair

Based on <http://martin.kleppmann.com/2013/05/24/improving-security-of-ssh-private-keys.html> and <http://pthree.org/2013/05/27/strengthen-your-private-encrypted-ssh-keys/>.