(Apologies if this has been done to death in the past - I can imagine
Ned sighing about protracted discussions prior to RFC1847 - but I
couldn't find any discussion in the archives)
RFC2311 (SMIME) and RFC1847 (upon which PGP/MIME has been based) only
allow MIME headers to be protected by the encryption process. Was there
any discussion during the preparation of RFC1847 about the possibility /
desirability / feasibility of allowing general RFC822 headers to be
included in the encrypted part of the message?
The most obvious candidates for headers to be encrypted along with the
MIME headers would be Subject: and Disposition-Notification-To: (the
subject the sender may have intended to use may be too sensitive to use
as the subject of the open message: the sender may want any MDN to be
sent only when the message is decrypted), though cases could probably be
made for just about any RFC822 header.
Could (and should) any replacements for RFC2015 and RFC2311 be amended
to allow RFC822 headers to be sent encrypted, and for the decryption
process to swap any encrypted headers found with the corresponding
headers in the actual message?
As availability of encryption software becomes more widespread, many
end-users may find SMIME/PGP most useful as simply a transport security
mechanism rather than a way of securely storing messages. In any case,
MUAs implementing PGP or S/MIME probably already allow the user to save
the decrypted version of a message.
It would be good if there were an interoperable way of making the
stored, decrypted message reflect the message the author would have
liked to send in the first place. It would be particularly nice if the
author could transmit the intended subject of a message when this may be
too sensitive to put in the open message headers.
--
Ian Bell T U R N P I K E Ltd