[freenet-dev] Why getting rid of HTL is bad was Re: Vulnerability in inserting the manifest before finishing

[Matthew Toseland]

On Thursday 03 January 2008 01:35, Michael Rogers wrote:
> Matthew Toseland wrote:
> > No, but it would make the request time variance much higher, especially 
for 
> > inserts and unsuccessful requests (which can potentially visit the entire 
> > network).
> 
> True, the variance would be higher. Visiting the entire network is a bit
> of an extreme example though - in theory it's also possible with the
> current hop counter, but it's not exactly likely. :-)
> 
> > A lot more requests will naturally timeout than do now, and therefore a 
node 
> > can silently drop a request without arousing much concern or suspicion. 
Per 
> > node failure tables can't reroute that key until the timeout happens, and 
if 
> > the timeout is larger than it is now, that takes longer.
> 
> We're using a reliable transport between nodes, so the only things that
> should cause a timeout are overloaded, crashed or faulty nodes. 

Not true. Very long paths can also cause this.

> If we 
> can keep the ping time under control then we can detect crashed nodes
> quickly. So with proper load management we should be able to pretty much
> eliminate timeouts except in the case of faulty nodes, which can then be
> detected.

Not with probabilistic termination.
> 
> >> I shouldn't have said we can't analyse it, but I wouldn't know where to
> >> start because so much depends on the topology. For example, the
> >> closest-location-so-far obviously leaks information, but how do we
> >> quantify it?
> > 
> > Isn't it similar to the situation with keys?
> 
> Sorry, I don't follow.
> 
> The closest-location-so-far tells an attacker something about the path a
> request has followed - among other things, it allows the attacker to
> rule out certain nodes the request definitely hasn't passed through. But
> how would we quantify that in terms of the size of the initiator's
> anonymity set or the probability that a given node is the initiator, for
> example?

Well, how does the attacker rule out previous nodes? How many can he rule out?
> 
> Whereas with a weighted coin, if the probability that each node
> terminates the request is 1/n then there's a 1/n chance that the
> previous hop is the initiator.
> 
> Cheers,
> Michael
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