[ietf-dkim] Base issue: multiple linked signatures
dotis at mail-abuse.org
Wed Dec 27 07:35:43 PST 2006
On Dec 26, 2006, at 5:24 PM, Hallam-Baker, Phillip wrote:
> I don't quite see what the objective is here.
> There is a lot of information that a sufficiently dedicated client
> might infer from multiple signatures made by the same signer but I
> am not sure that there is much value to be gained unless particular
> multiple signature practices are in widespread use.
The vast majority of email is spam. It will not take much to cause
DKIM verification to be switched off once a common practice of using
multiple signatures offers a means to hide. There are millions of
new domains added every day. The current DKIM spec in section 4
recommends damaged signatures not be removed. This means a good
actor might leave dead signatures in messages. The current mindset
then assumes the signing-domain and the email-address being added are
within the same domain.
The continuing assumption that the email-address domain and the
signing-domain are one-and-the-same also demands an unmanageable
exchange of private-keys or the delegation of domains. While this
requirement places greater control into the hands of major providers,
this does absolutely nothing in helping abate abuse, just the
opposite. It would also raise costs associated with the use of
domains not provided by the email-provider. Added administration and
costs will mean that DKIM is not a scalable solution for email. A
minor change can make a world of difference in this regard.
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