File encryption in emacs?

[Dr. Evil]

Has anyone created a package which allows emacs to access encrypted
files?  In other words, the file is stored on disk in encrypted format
(maybe with AES), and when I find it, emacs prompts for a decryption
password, decrypts it, and allows me to edit it.  Then, when I save
the file, it is saved in its encrypted format again.

Specificly, I would like to use this to encrypt my RMAIL file, if
that's possible.

(Note: Before I get a lot of responses aying, "that's useless, on a
multi-user machine, anyone with root can read your file by reading
from swap, etc", yes, I am aware of that, and this is not a multi-user
machine, and it is in a location which is not physically secure, so I
want to be able to save important data in an encrypted format.  Some
of you will also respond, "why don't you do it at the OS or FS layer",
and I am also aware of that, but very few OSes support FS encryption
in a useful way, and until they do, encryption at the application
layer is better than risking having no encryption.  Finally, some of
you may be tempted to respond, "use GPG and mailcrypt", which I
already do, but that addresses a different problem.)

Thanks