Re: [dane] Feature creep for draft-ietf-dane-smime

Warren Kumari <warren@kumari.net> Thu, 13 February 2014 20:43 UTC

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Date: Thu, 13 Feb 2014 15:43:27 -0500
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From: Warren Kumari <warren@kumari.net>
To: dane@ietf.org
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Subject: Re: [dane] Feature creep for draft-ietf-dane-smime
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On Thu, Feb 13, 2014 at 1:24 PM, Viktor Dukhovni
<viktor1dane@dukhovni.org> wrote:
> On Thu, Feb 13, 2014 at 06:19:15PM +0000, Osterweil, Eric wrote:
>
>> > Either way of computing the hash of the full address, rather than
>> > just the local part adds no complexity, and makes off-line attacks
>> > more difficult (per site dictionaries, rather than global dictionaries).
>> > This is a free win.  There's simply no reason not to.
>>
>> I have to say that I agree with Paul here.  I think the epsilon
>> increase in security is nice, but not at the cost of the additional
>> operational complexity.  However, the hashing-only approach has
>> the nice side effect of fixing the label length.  That _does_ seem
>> to solve a problem w/o some of the additional complexity.  My vote
>> would be hashing-only approach over Base32 and HMAC.
>
> In an off-list IM discussion, Paul H. and I reached consensus on
> local-part only hashing.  His argument is based on the introduction
> of root zone DNAME RRs that create equivalence between large subtrees
> of the DNS namespace.

Doh! Yeah, that's a really good point -- there have been a number of
similar discussions recently where DNAME has thrown a spanner into the
works / hasn't been considered.

W
> Users will likely expect these to result in
> equivalence of email addresses, ... so having SMIMEA lookup labels
> that work relative to multiple equivalent domain FQDNs is then a
> requirement.
>
> So I withdraw the suggestion to salt the lookup key with the domain.
>
> --
>         Viktor.
>
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