[Ietf-dkim] Tolerating Mailing-List Modifications I-D

[Wei Chuang <[e-mail]>]

Hi folks,
Being able to reverse mailing-list message modifications to repair the
message and enable digital signature verification, would resolve a
significant roadblock for further DMARC deployment.  Potentially it would
allow better attribution of which party contributed which content in the
message.  I propose some ideas around reversible mailing-list message
modifications in:
https://datatracker.ietf.org/doc/html/draft-chuang-mailing-list-modifications-00.
These modifications are: 1) prepending a description string to the Subject
header, 2) rewriting the From header, 3) removing the original
DKIM-Signature and 4) appending a footer to the message body.  (Apologies
that -00 draft is still in a rough form)

The idea of tolerating mailing-list modification by applying a reversible
transform has been proposed before such as:
https://datatracker.ietf.org/doc/draft-kucherawy-dkim-transform/
The approach in draft-chuang-mailing-list-modifications is to take a
smaller subset of the mailing-list changes in the transform draft but add
more descriptive detail around the changes.  It also builds on top of ARC
to tolerate multiple mailing-lists and uses
draft-chuang-replay-resistant-arc to provide path authentication.

-Wei