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Date:   Fri, 5 Jul 2019 16:51:11 +0800
From:   Herbert Xu <herbert@gondor.apana.org.au>
To:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc:     Milan Broz <gmazyland@gmail.com>,
        Eric Biggers <ebiggers@google.com>,
        device-mapper development <dm-devel@redhat.com>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@vger.kernel.org>
Subject: Re: [PATCH 3/3] dm-crypt: Implement eboiv - encrypted byte-offset
 initialization vector.
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On Fri, Jul 05, 2019 at 08:32:03AM +0200, Ard Biesheuvel wrote:
>
> > AFAICS this is using the same key as the actual data.  So why
> > don't you combine it with the actual data when encrypting/decrypting?
> >
> > That is, add a block at the front of the actual data containing
> > the little-endian byte offset and then use an IV of zero.
> >
> 
> That would only work for encryption.

True.  So this doesn't obviate the need to access the single-block
cipher.  But the code probably should still do it that way for
encryption for performance reasons.

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