Could you explain how the following detached signature would be
encoded using RFC1847/RFC2015? Would you use multipart/signed or
multipart/encrypted?
multipart/signed, with no encoding for clear text. For opaque signing we
could either encode it with base64 or sign & encrypt.
This is not what I meant by a detached signature. PGP supports the
concept of a signature which can be sent around independently of the data
it signs. For example, I could request that someone send me a signature
on some data I received earlier. They could create a signature on the
data and send it to me, without having to re-send the data itself.
Existing facilities can be used to do detached MIME signaturues. Specifically,
one constructs a message/external-body MIME object that contains a
content-md5 field describing the external data. One then signs this
part. The result is a detached signature that also contains a pointer
to the actual data which has been signed.
If you don't want the pointer then the right answer is to define a
MIME type for a existing PGP detached signature object.
Ned