On Fri, 10 Jul 2020, Matt Corallo via mailop wrote:
For various reasons, DKIM's non-repudiation property has always
prevented us deploying DKIM signing on our mail. The obvious fix for
this is to roll DKIM keys aggressively (eg every few minutes) and
publish the private keys for revoked keys as you go. Given relay
times for mail through various hosts, how aggressive could one
theoretically get without having keys time out before mail is
verified (ie how long must DKIM keys remain valid after mail has
been signed by them?).
How does this thinking go ?
You use a dedicated ip address whose name clearly identifies the customer.
You publish the private key and *do not* roll it over (more often than everyone
else).
You are a low volume sender and don't stick your head above the parapet,
so no one bothers to make an exception to the DKIM pass.
The "maths" is simple enough for the judge and jury.
there is a little misuse by spammers, so the client has plausible deniability.
Problems:
Spammers misuse you in large volume so you become visible to mail operators
and get blocked. Yes, that is a risk that the client signs up for.
You can roll the keys to be a good netizen, but that makes plausible
deniability less tenable ...
----------------
Can you have two DKIM signatures, RSA and ECC ?
If so does the following work ?
You can use the simple hash-based revokation to roll the ECC key
and limit the spam enabled by a fixed known RSA key.
I'd be asking danager money for the active effort with all this
key-rolling to let the client have their cake and eat it ...
--
Andrew C. Aitchison Kendal, UK
[email protected]
_______________________________________________
mailop mailing list
[email protected]
https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop
