[chord] Chord and hardness assumptions

[Tiago Vignatti]

Derrick Coetzee escreveu:
> Hi, I was recently reading the /Chord/ paper at 
> http://www.sigcomm.org/sigcomm2001/p12-stoica.pdf and a particular point 
> confused me: section 4.2 claims that a uniform distribution of keys and 
> nodes is justified by the assumption that cryptographic hash functions 
> cannot be inverted; but to break the system, it suffices to find a way 
> of generating keys that hash into a small range of the identifier space. 
> One really straightforward and general way to do this is to generate 
> random keys and discard the ones that don’t hash into the desired range. 
> It’s also possible that any particular cryptographic hash function may 
> possess a weakness that allows the generation of keys more likely to map 
> into a particular range (for example, an attack that fixes some of the 
> high order bits); but that range would still be large enough that this 
> wouldn’t facilitate inversion. So it seems like a stronger assumption is 
> needed than the standard ones. This paper has been around a while now 
> and I’m sure you’ve gotten this question before – is there another 
> publication discussing this limitation? Thanks for any information.

it reminds me the recently OpenSSL fiasco...


Cheers,

-- 
Tiago Vignatti
C3SL - Centro de Computação Científica e Software Livre
www.c3sl.ufpr.br