[tahoe-dev] Tahoe-LAFS Weekly Conference report, 2012-09-25

[David-Sarah Hopwood]

On 27/09/12 16:27, Zooko Wilcox-O'Hearn wrote:
> Topic: proof-of-storage/proof-of-retrievability
> 
> CiC suggested a pass-through "Chess Grandmaster" style attack of
> storage server which doesn't hold the data but queries other servers
> to answer challenges.

Interesting! I missed this part of the call.

> amiller suggested that perhaps not knowing the verify cap would
> prevent a storage server from doing that.

In Rainhill we wanted that:
a) the shares are (shallowly) self-verifiable.
b) a file can be repaired (i.e. all shares reconstructed) knowing
   only the verify-cap/SI.

I think these properties are directly in conflict with preventing the
pass-through attack, and are more important than it.

Note that with the PoS protocol, you can probe for knowledge of
particular shares, but you can't prevent the attacker from
reconstructing those from k other shares. So it's really a proof
of knowledge rather than a proof of storage.

-- 
David-Sarah Hopwood ⚥

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