[9fans] unix rsa-key with passphrase vs. p9(p)

[Rudolf Sykora <rudolf.sykora@gmail.com>]

On 8 March 2013 17:08, Rudolf Sykora <rudolf.sykora@gmail.com> wrote
> I now see that 9 ssh-agent is really only to deal with passphrases of
> the dsa/rsa keys.

Well, I seem to be wrong again. And have more questions...

In linux, ssh-agent takes care about an (optional) passphrase which
was used to cypher
the public (and perhaps also private, I believe) keys (so that eg the
admin can't abuse these)
generated by ssh-keygen; these keys are usually stored under $HOME/.ssh.

What do I have to do in order to use "9 ssh-agent" (which uses
factotum) when I have
the keys already generated (and their public parts distributed) by
linux's ssh-keygen?
(Ie I have id_rsa and id_rsa.pub in .ssh; and I use a passphrase.)

Particularly, there is some information given in p9p's rsa(1):
----------------
 Convert existing Unix SSH version 2 keys instead of generat-
          ing new ones:

               cd $HOME/.ssh
               pemdecode 'DSA PRIVATE KEY' id_dsa | asn12dsa >dsa2
               pemdecode 'RSA PRIVATE KEY' id_rsa | asn12rsa >rsa2

          Load those keys into factotum:

               cat rsa1 rsa2 dsa2 | 9p write -l factotum/ctl
----------------

but my keys are protected with a passphrase, so these commands do not
directly work. What must I do?

Finally, is there any reason to prefer the factotum way rather than the linux's
way just with ssh-keygen (with a passphrase) + ssh-copy-id + (linux's)
ssh-agent?

Thanks!
Ruda