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Re: [dm-devel] [PATCH] dm-crypt: disable block encryption with arc4



On 01/26/2010 10:22 AM, Sebastian Andrzej Siewior wrote:
> * Milan Broz | 2010-01-25 19:39:11 [+0100]:
>> On 01/25/2010 07:29 PM, Mikulas Patocka wrote:
>>> When using arc4 to encrypt a block device, the resulting device is 
>>> unreliable. It reads garbage. That's because arc4 is a stream cipher, if 
>>> you write something, it advances its state and if you attempt to decrypt 
>>> the same sector, it uses new state that is different.
>>>
>>> This patch disables the use of arc4 on block devices.
>>
>> arc4 again. it is simply not a block cipher:-)
>>
>> This should be solved inside cryptoAPI and not blacklist it in dm-crypt,
>> see that thread
>> http://article.gmane.org/gmane.linux.kernel.cryptoapi/3441
> 
> I some how remember Herbert saying to test for block size > 1. Wouldn't
> this be acceptable to block all stream cipher in one go?

yes, I think it is better.
(...and I just forgot to add that test to dm-crypt after that suggestion.)

Milan


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