Re: [Dcrup] I-D Action: draft-ietf-dcrup-dkim-usage-00.txt

["Murray S. Kucherawy" <[e-mail]>]

On Mon, Jun 5, 2017 at 9:53 AM, Scott Kitterman <[e-mail]>
wrote:

> I hear you.  I expect this to be the most contentious part of the draft.
>
> Here's my counter argument:
>
> The first DKIM RFC (RFC 4871), published in 2007 said:
>
> > Signers MUST implement and SHOULD sign using rsa-sha256
>
> I believe that the only reason rsa-sha1 was included at all was to make
> transition from domainkeys easier (see RFC 4870).  That's also (as I
> understand it where the 512 bit minimum key size came from).
>

As I recall, there were also implementations of DKIM made during its
development (even before its IETF time) that supported both, and defaulted
to rsa-sha1 because support for SHA256 in OpenSSL was new and not
universally deployed.  Some of them were still running in the wild, and
SHA1 wasn't fully deprecated, so the choice was made to be inclusive while
encouraging use of the newer stuff as much as possible.


> As a working group document editor, I'll change it however the group wants
> (of
> course), but I think we should either kill rsa-sha1 entirely in this
> document
> or leave it out entirely and let one of the follow-on documents add a new
> algorithm and remove rsa-sha1.  Preferably a clean kill or, failing that,
> not
> at all is what I think we should do.
>

I would omit it from the updated version entirely, and mark it "obsolete"
in the registry.

-MSK, from the floor