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Date: Wed, 05 Aug 2009 15:09:59 +0200
From: Milan Broz <mbroz@redhat.com>
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Subject: Re: [dm-crypt] cryptsetup with arc4 cipher
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To: Stelios Bounanos <sb-lst@enotty.net>
Cc: dm-crypt@saout.de, linux-crypto@vger.kernel.org

Stelios Bounanos wrote:
> I was surprised to see arc4 perform so badly, particularly since
> "openssl speed" results tell a very different story.  I decided to do
> some simple benchmarking of my own but I can't seem to get cryptsetup to
> work with arc4:
> 
>   # cryptsetup luksFormat --align-payload=512 -q -c arc4 /dev/sda4 key
>   # cryptsetup luksOpen -d key /dev/sda4 ctest
>     Command failed: No key available with this passphrase.
> 
> The above commands work fine with aes.  I can see arc4 in /proc/crypto.
> 
> Any ideas?

There is apparently some problem in kernel, not sure if dm-crypt or crypto
api one, This ARC4 configuration is allowed (no errors) but produces something
more like random generator:-)

one sector device:
# dmsetup create x --table "0 1 crypt arc4-cbc-plain 0123456789abcdef 0 /dev/sdb 0"

# sha256sum /dev/mapper/x
d37afeeb57a60b69715edd99f2a1523e77f6be51a1c61c56efc91ed691c90dfc  /dev/mapper/x

# sha256sum /dev/mapper/x
fdc87e8e9f158d26e58c5b48c80375b56cc24d0c088872f4aacc7e19fb5c5599  /dev/mapper/x

Not sure what's wrong yet...

Milan
--
mbroz@redhat.com