ietf-smime
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Re: SignedAttribute for Mime-Type

2005-12-13 14:30:47

  I would think that this would be a sensible thing for which to
use the 'ContentHints' attribute (see ESS clause 2.9).  You could
use 'id-data' in the 'contentType' field and the appropriate MIME
type in the 'contentDescription'.  I realize that ESS seems to
except the data content type from use of Content Hints, but I do
not believe this is proscriptive (there isn't a "SHOULD NOT").
  Why is something more required?

Hi Chris:

This is a excellent suggestion, that would meet my needs.  :-)
My only concern is that the UTF8String contentDescription appears
to somewhat vague.

Should I prepend the MIME type for the content with a text qualifier
in the contentDescription?

As an example, consider a CMS SignedData structure for a digital
signature of an MS word document.

Should I specify "Content-Type: application/msword" or just
"application/msword" in the contentDescription of the ContentHints
attribute?

Also on a side note, digital signatures can be nested.  For CMS
SignedData objects, there is no office media type:

        http://www.iana.org/assignments/media-types/index.html

The closest match is for PKCS7 signatures:

        application/pkcs7-signature

However, its usage as specified in RFC-2311 can deviate from generic
CMS.  Prehaps we need to have an "application/cms-signature" media
type.

Thanks again Chris for your excellent suggestion!  :-)
Alicia.

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