On 07/11/2012 04:22 PM, Bob Friesenhahn wrote:
> On Wed, 11 Jul 2012, Sašo Kiselkov wrote:
>> the hash isn't used for security purposes. We only need something that's
>> fast and has a good pseudo-random output distribution. That's why I
>> looked toward Edon-R. Even though it might have security problems in
>> itself, it's by far the fastest algorithm in the entire competition.
> If an algorithm is not 'secure' and zfs is not set to verify, doesn't
> that mean that a knowledgeable user will be able to cause intentional
> data corruption if deduplication is enabled?  A user with very little
> privilege might be able to cause intentional harm by writing the magic
> data block before some other known block (which produces the same hash)
> is written.  This allows one block to substitute for another.
> It does seem that security is important because with a human element,
> data is not necessarily random.

Theoretically yes, it is possible, but the practicality of such an
attack is very much in doubt. In case this is a concern, however, one
can always switch to a more secure hash function (e.g. Skein-512).

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