Subject: Re: Information and meta-information

From: Wim Lewis <[email-masked]>
Date: Wed, 7 Sep 2005 15:56:58 -0700

On 31 Aug, 2005, at 8:26 AM, Daniel A. Nagy wrote:
> There is no distinction between PGP/MIME data and regular RFC2440  
> data,
> although all it would take is a flag in the Literal packet. This  
> way, if I
> saved the PGP MESSAGE from an application/pgp-encrypted MIME chunk  
> (which is
> doable even with MUAs ignorant of PGP/MIME), I could still decrypt  
> it into a
> usable file (e.g. a jpeg image).

I have had exactly the same thought (down to the choice of an 'm' in  
that field to indicate MIME data). This seems like a good idea in  
general. It would be useful outside of PGP/MIME as well: if metadata  
such as datatype or character encoding needs to be associated with  
the PGP-protected data, it seems reasonable to piggyback on MIME,  
just as (e.g.) HTTP does.

The existing 'b', 't', etc. tags could then be defined as shorthands  
for particular MIME headers (content-type and charset).

> I would suggest the following modification of RFC2440bis-14:

Do you mean removing the 't' and 'u' tags? Or supplementing them with  
'm'?

---

From: [email-masked] (Daniel A. Nagy)
Date: Thu, 8 Sep 2005 01:31:25 +0200

> for particular MIME headers (content-type and charset).

I disagree, because these tags convey a slightly different (lower-level)
meaning than the mime headers. Also, the above suggestion would be a
security hazard, since the literal packet's tag is not hashed and can be
therefore altered in a signed message, without breaking the signature.
PGP/MIME headers, on the other hand, are included in the hashed material, so
they are part of the signed message.

> Do you mean removing the 't' and 'u' tags? Or supplementing them with  

Supplementing with 'm', of course. Removing 't' and 'b' tags (what's 'u'?)
would break almost everything.

-- 
Daniel

---

From: David Shaw <[email-masked]>
Date: Tue, 20 Sep 2005 14:08:23 -0400

> would break almost everything.

't' = unspecified charset
'u' = utf-8 charset

David