One of the things I like most about PEM, as compared to say X.400,
is that although it is mail-oriented, it does not require a mail-based
system. I can, if I wish, walk down the hall with a PEM-encrypted
and digitally signed "message" that can contain anything at all,
even a spreadsheet or a video file, and I can verify the contents.
I would hope that the much desired integration of PEM and MIME
would maintain that very useful feature. Syntactical conventions
can be established that delineate various body parts, but I
would hope that a way can be found to ship that entire
conglomerated "thing" around the world using any means that
I wish.