I’ve posted a followup to this article that discusses ssh-agent.
For reasons best left to another post, I wanted to convert an SSH public key into a PKCS#1 PEM-encoded public key. That is, I wanted to go from this:
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQD7EZn/BzP26AWk/Ts2ymjpTXuXRiEWIWn
HFTilOTcuJ/P1HfOwiy4RHC1rv59Yh/E6jbTx623+OGySJWh1IS3dAEaHhcGKnJaikrBn3c
cdoNVkAAuL/YD7FMG1Z0SjtcZS6MoO8Lb9pkq6R+Ok6JQjwCEsB+OaVwP9RnVA+HSYeyCVE
0KakLCbBJcD1U2aHP4+IH4OaXhZacpb9Ueja6NNfGrv558xTgfZ+fLdJ7cpg6wU8UZnVM1B
JiUW5KFasc+2IuZR0+g/oJXaYwvW2T6XsMgipetCEtQoMAJ4zmugzHSQuFRYHw/7S6PUI2U
03glFmULvEV+qIxsVFT1ng3pj lars@tiamat.house
To this:
-----BEGIN RSA PUBLIC KEY-----
MIIBCgKCAQEA+xGZ/wcz9ugFpP07Nspo6U17l0YhFiFpxxU4pTk3Lifz9R3zsIsu
ERwta7+fWIfxOo208ett/jhskiVodSEt3QBGh4XBipyWopKwZ93HHaDVZAALi/2A
+xTBtWdEo7XGUujKDvC2/aZKukfjpOiUI8AhLAfjmlcD/UZ1QPh0mHsglRNCmpCw
mwSXA9VNmhz+PiB+Dml4WWnKW/VHo2ujTXxq7+efMU4H2fny3Se3KYOsFPFGZ1TN
QSYlFuShWrHPtiLmUdPoP6CV2mML1tk+l7DIIqXrQhLUKDACeM5roMx0kLhUWB8P
+0uj1CNlNN4JRZlC7xFfqiMbFRU9Z4N6YwIDAQAB
-----END RSA PUBLIC KEY-----
If you have a recent version of OpenSSH (where recent means 5.6 or later), you can just do this: