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From:   Gilad Ben-Yossef <gilad@benyossef.com>
Date:   Fri, 30 Oct 2020 13:20:41 +0200
Message-ID: <CAOtvUMdJxVSFhN4QMNL+eiF6OB2LevThcgDK34M-=JDXCoDXMA@mail.gmail.com>
Subject: Re: [PATCH v3 1/4] crypto: add eboiv as a crypto API template
To:     Milan Broz <gmazyland@gmail.com>
Cc:     Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Alasdair Kergon <agk@redhat.com>,
        Mike Snitzer <snitzer@redhat.com>,
        device-mapper development <dm-devel@redhat.com>,
        Ofir Drang <ofir.drang@arm.com>,
        Eric Biggers <ebiggers@kernel.org>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Hi,

On Fri, Oct 30, 2020 at 12:33 PM Milan Broz <gmazyland@gmail.com> wrote:
>
> On 29/10/2020 11:05, Gilad Ben-Yossef wrote:
> >
> > +config CRYPTO_EBOIV
> > +     tristate "EBOIV support for block encryption"
> > +     default DM_CRYPT
> > +     select CRYPTO_CBC
> > +     help
> > +       Encrypted byte-offset initialization vector (EBOIV) is an IV
> > +       generation method that is used in some cases by dm-crypt for
> > +       supporting the BitLocker volume encryption used by Windows 8
> > +       and onwards as a backwards compatible version in lieu of XTS
> > +       support.
> > +
> > +       It uses the block encryption key as the symmetric key for a
> > +       block encryption pass applied to the sector offset of the block=
.
> > +       Additional details can be found at
> > +       https://www.jedec.org/sites/default/files/docs/JESD223C.pdf
>
> This page is not available. Are you sure this is the proper documentation=
?

You need to register at the JEDEC web site to get the PDF. The
registration is free though.

It's the only standard I am aware of that describe this mode, as
opposed to a paper.

>
> I think the only description we used (for dm-crypt) was original Ferguson=
's Bitlocker doc:
> https://download.microsoft.com/download/0/2/3/0238acaf-d3bf-4a6d-b3d6-0a0=
be4bbb36e/bitlockercipher200608.pdf


Yes, the JEDEC has a reference to that as well, but the white paper
doesn't actually describe the option without the diffuser.

>
> IIRC EBOIV was a shortcut I added to dm-crypt because we found no officia=
l terminology for this IV.
> And after lunchtime, nobody invented anything better, so it stayed as it =
is now :-)

Well, I still don't have any better name to offer, LOL :-)

Gilad


--=20
Gilad Ben-Yossef
Chief Coffee Drinker

values of =CE=B2 will give rise to dom!