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I have submitted a revision to the DKIM2 specification document

   https://datatracker.ietf.org/doc/draft-clayton-dkim2-spec/

This new version places the recipes, the SMTP parameters and the crypto
into JSON objects which are then base64 encoded and put into the
Message-Instance and DKIM2-Signature fields. This was originally
Tobias's idea and it has worked out well (if a little slowly).

Other values have been left as tag=value so that human readers of email
headers (who are not all that common of course) can get an idea of what
is going on. People who feed messages into tools that then present the
information in the header fields in a human-friendly way will not of
course care one way or the other!  Anyway, it's obviously possible to
move more values in or out of the JSON.

The recipes are complex and JSON is much more straightforward for
systems to parse. They are a separate object so that you can easily see
they are there (and get a feel for how complicated they might be).

Putting the crypto (hashes and signatures) into the JSON means that the
bodge of a1= a2= etc disappears and I have removed the restriction on
just two hash/signature algorithms. We might want to set an upper bound
mind you.

Putting the SMTP parameters into JSON does not help the human readers of
headers (albeit they are no worse off than with DKIM1 since this is a
new feature of DKIM2). However, if we don't do that then as Hannah so
helpfully pointed out you need a fully-fledged RFC5321 parser in order
not to misinterpret the superficially easy to parse tag=value format.

I also removed the restriction on no recipes on the v=1 Message-
Instance. It is argued that being able to recreate the message as it was
before it entered the DKIM2 world would be useful ... one could see if
was an OK DKIM1 message for example, and this might make it easier for
people to handle messages from mailing lists which were DKIM2 enabled
but not all the messages submitted to them were DKIM2 messages.

I have not yet had time to take up Dave Crocker's excellent suggestion
to have a section not just on Signers and Verifiers but also on what
Forwarders should be doing. I also aim to reorganise the sections a bit
(to put the algorithms for creating hashes alongside the description of
the JSON blobs to hold the results). This might reduce some of the
repetition that remains in the document.

BTW: the four JSON schemas are valid JSON -- but that does not mean that
they are correct :-)   ... and I will be sorting out the dangling URLs
very shortly.

- -- 
richard @ highwayman . com                       "Nothing seems the same
                          Still you never see the change from day to day
                                And no-one notices the customs slip away"

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