Does GnuPG implement MIME support?

Thomas Roessler roessler at
Sat Jul 15 10:18:17 CEST 2000

On 2000-07-14 20:43:47 -0700, Nathan Thompson-Amato wrote:

> I'm wondering if GnuPG implements MIME support, as in
> RFC 2015 (, or if
> this is left to the MUA.

As far as I know, it's left to the MUA, and that's
actually a good thing: As soon as you have a MUA whith
reasonably decent MIME support, you don't want the crypto
back-end to get into your way, MIME-wise.

Just write the complete MIME-formatted body (including
MIME headers!) out to the back-end, and let the back-end
create the signature or encrypted data.

When doing PGP/MIME signing, just encapsulate the
MIME-formatted body and the signature in a

When doing encryption, just encapsulate PGP's output in a
multipart/encrypted body part.

It's not that hard.

Note, BTW, that forwarding messages as message/rfc822 body
parts can get kind of tough when you are signing: With
PGP/MIME, you have to make sure that you stick with
_strict_ MIME, and avoid _any_ 8bit encodings.

Additionally, you MUST NOT (really, the RFCs are quite
strict about it, and it's making things greatly less
complex for MUA code) use base64 or quoted-printable for
any composite body parts (message/rfc822, multipart/*).
This means that you may have to redo the forwarded
message's innermost attachments' MIME encoding.

An additional gotcha: Please make sure you generate "text"
signatures, as opposed to "binary" signatures (with PGP 2,
that's "pgp -st").  This is important for some issues
concerning trailing whitespace and one-pass verification.
The standard doesn't say anything about it, yet, but this
is an issue which will have to be resolved before RFC
2015bis comes out.  Since current implementations
generally generate text signatures, you'll be on the safe
side that way.

> I ask because I'm going to try my hand at implementing
> transparent GnuPG/PGP support in Evolution
> (, and I'd
> like to clarify just how much work I should expect
> GnuPG to do for me.

What's on your web pages looks nice, though _very_
Outlook-like. ;-)

Will Evolution's calendar be able to read ical ~/.calendar
files? (Not iCalendar, you say that, but ical, like in

Thomas Roessler              <roessler at>

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