Subject: [ietf-dkim] EAI and DKIM(was Re: Proposed new charter)

From: Takaaki Higuchi <[email-masked]>
Date: Wed, 3 Mar 2010 08:51:47 +0900

Hi, David,

Being on this list a year or more, this is my first post here. Thank you
for rasing this point in this list so quickly. And I raised the problem of
EAI(E-mail Address Internationalization) at APCAUCE meeting(and
back to Tokyo now), so I'd like to clarify the point as much as I can,
though I am not an expert in this area.

Fist of all, I don't think IDN has interoperability problems with DKIM.
IDN is designed not to affect any impact to existing DNS system.
(So punycode encoding, which encodes unicode to ascii, is used)

At first, I thought EAI is only extend IDN punycode to local part of E-mail
address. But it is wrong. EAI extends SMTP to express full E-mail address
as internationalized.

My rough understanding is that EAI is put e-mail address into From: with
both unicode encoded and current style. When recipient SMTP server
does not support EAI, it downgrades to connect to the recipient.
Which means delete unicode part from From: hearder. That makes DKIM
verification breaks.

thanks in advance,
Takaaki Higuchi, Anti-spam committe, Internet Association Japan

On Mon, Mar 1, 2010 at 6:24 PM, Dave CROCKER <[email-masked]> wrote:
>
> This is perhaps more relevant to a discussion about interoperability testing,
> but I thought it worth raising also for the next round of specification, etc. work:
>
>    Do we know whether DKIM works IDNs?  If not, what should we do about that?
>
> (I'm sitting in Apricot and this came up during an APCauce discussion.)
>
> d/
>
> --
>
>   Dave Crocker
>   Brandenburg InternetWorking
>   bbiw.net

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---

From: SM <[email-masked]>
Date: Tue, 02 Mar 2010 16:33:58 -0800

>(So punycode encoding, which encodes unicode to ascii, is used)

If you consider that only A-labels are used for the "d=" tag, it does 
not affect the retrieval of the (DKIM) public key.  Selectors can be 
constrained similar to what is being done for service labels.

>address. But it is wrong. EAI extends SMTP to express full E-mail address

Yes.

>both unicode encoded and current style. When recipient SMTP server

Yes.

>Which means delete unicode part from From: hearder. That makes DKIM

There may be changes to Downgrade.  Both the experimental 
specification or its revision will cause DKIM verification failures 
when the message is downgraded.

DKIM signing and verification of UTF-8 headers will require a change 
in some implementations.  There will be more room for visual 
spoofing.  There is also the question of whether to use U-labels.

Regards,
-sm