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Re: [ietf-dkim] New Issue: bunch of nits on threats-01 document

2006-03-14 12:14:39

On Mar 13, 2006, at 5:23 PM, Jim Fenton wrote:

#7. s3.2.3 last sentence s/must be/should benefit from being/ The "must" seems a bit strong.

I don't want to soften the statement too much; I have already done so by saying that the identity has to be "fairly reliable". Is this another of those places where I slipped out of character and started to sound normative? I could instead say something like, "reputation systems are dependent upon the use of an identity that is, in practice, fairly reliable." Is that version better?

This aspect of identification becomes the basis for the disagreement with respect to the impact on message replay abuse. Accruing fair reputations indeed needs "fairly reliable" identifiers. In the case of a signature, the nature of the abuse must also be limited to the signed portion of the message.

This limitation creates a significant dilemma not considered in the threat review. Both the frequency and the recipient of the message must be excluded from a reputation assessment which emasculates any DoS protections the reputation history should provide. When the reputation accrual unfairly includes the envelope to restore DoS protections, then the impact resulting from abusive message replay affects the domain as a whole and should be deemed a high impact.

There is a solution that exists outside of DKIM, but must be mandated in conjunction with DKIM, or recipients remain highly prone to DKIM DoS attack.

-Doug



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