Re: [dm-crypt] XTS cipher mode limitations (FAQ additions)

[Christoph Anton Mitterer <christoph.anton.mitterer@physik.uni-muenchen.de>]

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Hi Arno.

Thanks for the other changes =)

On Mon, 2010-08-23 at 02:46 +0200, Arno Wagner wrote:
> Since I typically insist on that, I should have done this in 
> the first place.
;-)

> Diexed also for MB and kB. (No GB in there)
Yeah,.. I meant of course all of them =)


> > May I further suggest, that in all references to 2TB, we add "(= 2^32 *
> > 512 bytes)"?
> > There's always that problem that one never knows whether TB really means
> > TB or TiB.
> Instead changed all 2TB to 2TiB. 
I guess it could be still nice to show the "forumla"... so that people
know how that 2 TiB come together... (guess many don't know that dmcrypt
_always_ uses 512 byte blocks).


btw: That might even qualify for its own FAQ entry,... that it uses
always 512byte blocks, and that e.g. the number in the payload offset
from luksDump are also blocks.



> Well, if it comes up again, I can look at it.  I will 
> however not start to distribute my own FUD and I am 
> not a good enough cryptographer for a really thorough
> analysis of the issue. I am willing to read a paper on
> it if somebody else provides the link ;-)
Once you should add it... don't forget (which I just realised recently
^^) that it's about the written data in blocks,... not just the written
data itself, at least if I understand it correctly.

So say we _would_ have a hard limit on 1TB, and I'd just write 1 bit,
I'd still have "used up" 512 bytes from my safety buffer, before having
to re-encode, right?

btw: Milan, do you know about any paper dealing with that issue?


Cheers,
Chris.

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