The PEM guys seem to be going ahead with Base64 every time they need
a binary transfer of something.
This is a lousy method for human consumption, but one might think
of doing the "filename" stuff as
filename ::= <"> ascii-text <"> /
"64x" Base64Stuff
At least this minimizes the chance of hitting an existing file if the
client "forgets" to undo the encoding :-)
Harald A