GtkEntry supports a "secure" mode via gtk_entry_set_visibility() in which the
input typed by the user is hidden. However, this mode is not appropriate for
entering highly sensitive data like a GnuPG key passphrase as the data might
still be leaked to swap space. I therefore suggest adding a "high security mode"
in which all data containing the input (e.g. passphrase) is stored in unpageable
memory (the application must of course be suid root for that).

I already suggested to add the necessary memory allocation methods to glib [1].

An example for an application needing this "high security mode" is pinentry
(part of the Aegypten project). I hacked a really (hopefully...) secure GtkEntry
widget for it, using the pinentry methods for memory allocation [2], but I think
it might be useful for others, too.

[1] http://bugzilla.gnome.org/show_bug.cgi?id=151999
[2]
http://cvs.gnupg.org/cgi-bin/viewcvs.cgi/pinentry/gtk%2B-2/?cvsroot=Project+Aegypten