Re: [zfs] [Review] 4185 New hash algorithm support
----- Forwarded message from Pawel Jakub Dawidek
On 10/7/13 10:17 PM, Zooko Wilcox-OHearn wrote:
So, before I go on with my pitch for why you should consider BLAKE2, first please clarify for me whether ZFS really needs a collision-resistant hash function, or whether it needs only a MAC. I had thought until now that ZFS doesn't need a collision-resistant hash unless dedup is turned on, and that if dedup is turned on it needs a collision-resistant hash.
The reason is purely for dedup and pretty much nothing else. As such, we only need a hash with a good pseudo-random output distribution and collision resistance. We don't specifically need it to be super-secure. The salted hashing support I added was simply to silence the endless stream of wild hypotheticals on security.
Just FYI, Richard Yao just proposed providing VM images with existing ZFS pool also for production use. This is great idea, but also a nice proof why making assumptions on how exactly a general purpose software will be used is bad. In this case your salted hashing is pointless as everyone knows about the salt in those images. And we are back to square one. Saso, there are countless examples where so called hypothetical security bugs turned out to be exploitable in practise. Which is especially true for general purpose software that we have no control over how it is being used. As Zooko mentioned cryptoanalysis of the Edon-R algorithm stopped at the point where we know it is not cryptographically secure and this is unlikely we will see any further work in the subject, which in my eyes is even worse, as we don't know how bad is it. To sum up. Even if the OpenZFS community will agree to integrate Edon-R, I'll strongly oppose having it in FreeBSD. In my opinion it is just asking for trouble. I still like your change very much and would love to see new, cryptographically secure hash algorithms for dedup in ZFS. Currently there is no alternative, which is bad for security too. -- Pawel Jakub Dawidek http://www.wheelsystems.com FreeBSD committer http://www.FreeBSD.org Am I Evil? Yes, I Am! http://mobter.com ------------------------------------------- illumos-zfs Archives: https://www.listbox.com/member/archive/182191/=now RSS Feed: https://www.listbox.com/member/archive/rss/182191/22842876-6fe17e6f Modify Your Subscription: https://www.listbox.com/member/?member_id=22842876&id_secret=22842876-a25d3366 Powered by Listbox: http://www.listbox.com ----- End forwarded message ----- -- Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://ativel.com http://postbiota.org AC894EC5: 38A5 5F46 A4FF 59B8 336B 47EE F46E 3489 AC89 4EC5
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Eugen Leitl