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Re: Clogging attacks on SKIP
>Let me mention that if one really wants to, we _can_ give a complete solution
>to clogging in the non-interactive (SKIP) framework. Namely, require each
>request to be accompanied by
> MD5(IPaddresses, time, counter, x)
>where cnt is the counter of number of tries within the same `time' (which is
>roughly synchronized), and x is any number such that the last $l$ bits of the
>MD5 are zero.
Amir,
As I said when you described this to me in my office on your visit,
this *is* a really neat trick.
But I see a problem. We ideally want our KM protocol to be useable on
a very wide range of CPUs, from palmtops up through Crays. Most
mobile clients (where security is most important) are going to land
near the bottom of this range, especially when you consider that MD5
is highly optimized for 32-bit machines and doesn't run nearly as fast
on a 16-bit 8088 class palmtop. I.e., a hell of a lot slower than on
the 486s and Sparc-class workstations that a typical attacker would
probably use. So picking a value of $l$ that's sufficiently painful
for the swamper may also prove to be too painful for the low end
legitimate user.
Phil
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