So, if I had a block collision on my ZFS pool that used dedup, and it had my bank balance of $3,212.20 on it, and you tried to write your bank balance of $3,292,218.84 and got the same hash, no verify, and thus you got my block/balance and now your bank balance was reduced by 3 orders of magnitude, would you be okay with that? What assurances would you be content with using my ZFS pool?
Gregg Wonderly On Jul 11, 2012, at 9:43 AM, Sašo Kiselkov wrote: > On 07/11/2012 04:30 PM, Gregg Wonderly wrote: >> This is exactly the issue for me. It's vital to always have verify on. If >> you don't have the data to prove that every possible block combination >> possible, hashes uniquely for the "small" bit space we are talking about, >> then how in the world can you say that "verify" is not necessary? That just >> seems ridiculous to propose. > > Do you need assurances that in the next 5 seconds a meteorite won't fall > to Earth and crush you? No. And yet, the Earth puts on thousands of tons > of weight each year from meteoric bombardment and people have been hit > and killed by them (not to speak of mass extinction events). Nobody has > ever demonstrated of being able to produce a hash collision in any > suitably long hash (128-bits plus) using a random search. All hash > collisions have been found by attacking the weaknesses in the > mathematical definition of these functions (i.e. some part of the input > didn't get obfuscated well in the hash function machinery and spilled > over into the result, resulting in a slight, but usable non-randomness). > > Cheers, > -- > Saso _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
