Re: [gentoo-user] Luks: Which cipher to use

[Marco]

Hi Mike,

Thanks for your very detailed description and explanation!

On Wed, Sep 9, 2009 at 12:30 PM, Mike Kazantsev<mk.fraggod@×××××.com> wrote:
> On Tue, 8 Sep 2009 11:21:12 +0200
> Marco <listworks@×××××.com> wrote:

[...]

> ESSIV, on the other hand, uses the hash of these counters with the key
> itself to salt IV, so it seem to rule out all the aforementioned
> vulnerabilities. Hash strength here ensures that it can't be turned
> into former 'plain counters' case due to hash collision.
>
>
> XTS/LRW/CBC/... are methods to encrypt the single data block to a disk
> block. Since data is read in blocks, block also seem to be the atomic
> unit of data encryption - everything is en-/decrypted in whole blocks
> when read/written from/to disk.
>
> These methods further divide the disk block into a smaller units to
> ensure that there won't be a (similar to the above) case when two
> similar, say, 16-byte pieces in a single 512k disk block would look
> identical, otherwise some data with such watermarks can be generated
> and proven to be on this disk - whole blocks can be marked with them,
> so they can later be found, along with any known data between them.
>
> They also mix the key with some generated salt for these units.
> CBC relies on plain data, so it can be broken by crafted data. LRW also
> seem to suffer from some known vulnerabilities, so XTS seem to be the
> best and recommended one.

So I think I'll go with xts-essiv:sha256. In terms of performance, a
keylength of 256 might not be ideal. But since this external drive is
mainly thought as a backup device,this is not too much of a drawback.

--
Best regards,
 Marco