RFCs, standards, pink bunnies and flower patterns was -- Re: GPG Outlook Plug-In and Signatures

Ryan Malayter ryan at malayter.com
Tue Oct 17 17:11:17 CEST 2006

On 10/17/06, Nicholas Cole <npcole at yahoo.co.uk> wrote:
> --- Ryan Malayter <ryan at malayter.com> wrote:
> > Again I must state that one has little to do with
> > the other. MHTML's
> > MIME format may not play nice with PGP/MIME's
> > encapsultation format,
> > but it didn't *have* to be that way. S/MIME, for
> > example, seems to
> > make provisions for playing nicely with other MIME
> > structures such as
> > MHTML, as well as arbitrary attachments.
> What is it about the PGP/MIME spec that makes it not
> play nicely with HTML email?  Or vice versa?

I'm not sure, but it seems no MUA or plug-in I have tried handles it correctly.

> I've always assumed that lack of HTML support said
> more about the crypto crowd's preference for text
> email than some technical problem, but perhaps I was
> wrong...

This very well may be the case; it could just be an implementation
issue. PGP/MIME seems to be based on RFC1847, which states:

   ...The first body part may contain any valid MIME content
   type, labeled accordingly...

So, it would seem the "first body part" could be of type
multipart/alternative (HTML). But I am unsure; as
multipart/alternative is needed in the message header of an HTML
email. RFC 1847 requires "multipart/signed" or "multipart/encrytped"
in the message header. I think that may be what causes the troubles.

Whatever the case, I always seem to have issues with attachments and
HTML messages using PGP, but not with S/MIME. Although that may be a
result of the limited selection of MUAs and software I use at my
company. (Thuderbird, Outlook+GPGOL and Outlook plus the commercial
PGP Desktop v9).

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