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SubjectDM for detecting bad disks was: dm-crypt, new IV and standards
Pavel Machek wrote:
> Hi!
>
>
>>>>Well, CTR mode is not recommended for encrypted file systems because it is very
>>>>easy to corrupt single bits, bytes, blocks, etc without an integrity check.
>>>>If we add a MAC, then any mode of operation except ECB can be used for
>>>>encrypted file systems.
>>>
>>>what does "easy to corrupt" mean? i haven't really seen disks generate
>>>bit errors ever. this MAC means you'll need to write integrity data for
>>>every real write. that really doesn't seem worth it...
>>
>>The difference between "_1,000,000" and "_8,000,000" is 1 bit. If an
>>attacker knew enough about the layout of the filesystem (modify times on blocks,
>>etc) they could flip a single bit and change your _1Mil purchase order
>>approved by your boss to a _8Mil order.
>
>
> Hmm... long time ago I created crc loop device to catch
> faulty disks. If cryptoloop can do that for me... very good!

Yes, a crc, or some other very low overhead DM target would be great for
this. I haven't looked at DM too much. :( Does it already have
something like this already?
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