[BitTorrent] Back to Merkle Hash Trees... [no longer on topic, wandering into cryptography]

Nick Johnson arachnid at notdot.net
Wed Feb 9 18:23:06 EST 2005

On 8/02/2005, at 1:18 PM, Joseph Ashwood wrote:

> I agree that using a known broken hash is a bad idea, but not 
> preparing for
> the hash to be broken is like assuming you shouldn't wear your seatbelt
> because you've never crashed your car. By assuming that breaks will 
> happen
> you can make it more difficult to perform any break, leading to more
> resilient security.

And I still maintain that writing a system assuming the hash will be 
broken in certain ways is pointless. How can you know it won't be 
broken in another manner that your system doesn't counter?

Adding significant additional complexity to a protocol because you fear 
the breaking (in some specific manner) of the hash you use is hardly 
justified unless you both have evidence of the likelihood of this 
occurring and the reward from breaking it is high. In this case, 
there's (to the best of my knowledge) no significant evidence of 
attacks of this nature against SHA1, and the profit to an attacker from 
any one such attack is relatively low compared to the effort required. 
It's not worth making a protocol much more complex for.

-Nick Johnson

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