[tahoe-dev] "Elk Point" design for mutable, add-only, and immutable files

James A. Donald jamesd at echeque.com
Mon Oct 12 00:23:36 UTC 2009

Zooko O'Whielacronx wrote:
> We should think that issue through, along with the accompanying issue
> of "how low a chance of success is low enough".  If there are 2^50
> caps in use, and some technique can "attack all known caps at once",
> then do we need to increase the size of the caps (possibly by up to 50
> bits) to make it so that the chance of success against *any* target is
> still negligible?  Or is it just unreasonable to think that some
> adversary would spend massive amounts of computer power in order to
> forge some random cap out of a large set of caps? 

Obviously this depends on what caps are being used for.  For what caps 
are *now* being used for, no one would to forge some random cap out of a 
very large set of caps.

If caps were used for the purpose that the shared secret of a credit 
card is used for, *then* people would be interested in forging some 
random cap - but that is a new kind of cap, which could be defined with 
a new number of bits.

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