x11-ssh-askpass is an X11-based passphrase dialog for use with OpenSSH.

To utilize this service, you will need a private SSH key in ~/.ssh/
If you log on using kdm, then just create a ~/.xprofile with the
contents of /usr/doc/x11-ssh-askpass-1.2.4.1/xprofile.sample

If you are launching X from console (with startx), then you can edit your
~/.xinitrc to source ~/.xprofile or just add the contents of ~/.xprofile
to ~/.xinitrc to it. Of course, there are other acceptable ways to do
the same thing - gurus can roll their own.