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Date:   Fri, 19 Jul 2019 09:47:26 +0800
From:   Herbert Xu <herbert@gondor.apana.org.au>
To:     Pascal Van Leeuwen <pvanleeuwen@verimatrix.com>
Cc:     Milan Broz <gmazyland@gmail.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Horia Geanta <horia.geanta@nxp.com>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
        "dm-devel@redhat.com" <dm-devel@redhat.com>
Subject: Re: xts fuzz testing and lack of ciphertext stealing support
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On Thu, Jul 18, 2019 at 04:35:26PM +0000, Pascal Van Leeuwen wrote:
>
> Tthen there's still the issue of advancing that last tweak. From what I've seen,
> the xts implementation does not output the last tweak so you would have to 
> recompute it locally in cts.c as block_cipher_enc(iv) * alpha^j. Which is wasteful.
> Of course this could be solved by redefining xts to output the last tweak
> like CBC/CTR output their last IV ... Which would probably give us HW guys
> trouble again because our HW cannot do *that* ... (While the HW very likely 
> *does* implement the cipher text stealing properly, just to be able to boast
> about IEEE P1619 compliance ...)

If your hardware supports XTS properly then you wouldn't even need
to use this new template.  You would directly export the xts
interface.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt