[PATCH 0/2] crypto: talitos: Add AES-XTS mode

[Martin Hicks]

On Mon, Mar 9, 2015 at 6:16 AM, Horia Geantă <horia.geanta at freescale.com> wrote:
> On 3/3/2015 7:44 PM, Martin Hicks wrote:
>> On Tue, Mar 3, 2015 at 10:44 AM, Horia Geantă
>> <horia.geanta at freescale.com> wrote:
>>>
>>> For talitos, there are two cases:
>>>
>>> 1. request data size is <= data unit / sector size
>>> talitos can handle any IV / tweak scheme
>>>
>>> 2. request data size > sector size
>>> since talitos internally generates the IV for the next sector by
>>> incrementing the previous IV, only IV schemes that allocate consecutive
>>> IV to consecutive sectors will function correctly.
>>>
>>
>> it's not clear to me that #1 is right.  I guess it could be, but the
>> IV length would be limited to 8 bytes.
>
> Yes, there's a limitation in talitos wrt. XTS IV / tweak size - it's up
> to 8 bytes.
> So I guess ESSIV won't work with talitos-xts, since the encrypted IV
> output is 16 bytes.
> But as previously said, ESSIV breaks the XTS standard requirement for
> having a consecutive IV for consecutive blocks. ESSIV should really be
> used only with disk-level encryption schemes that require an
> unpredictable IV.

Ok.  I'll verify that the second half of the IV is zeroed.

One last thing that I'm not sure of is what string to place in
cra_ablkcipher.geniv field.   "eseqiv" seems wrong if plain/plain64
are the IVs that XTS is designed for.

Thanks,
mh

-- 
Martin Hicks P.Eng.      |         mort at bork.org
Bork Consulting Inc.     |   +1 (613) 266-2296