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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Thu, 21 Jan 2021 19:09:36 +0100
Message-ID: <CAMj1kXEycOHSMQu2T1tdQrmapk+g0oQFDiWXDo0J0BKg4QgEuQ@mail.gmail.com>
Subject: Re: [PATCH 5/5] crypto: remove Salsa20 stream cipher algorithm
To:     Eric Biggers <ebiggers@kernel.org>, agk@redhat.com,
        Mike Snitzer <snitzer@redhat.com>, dm-devel@redhat.com,
        Milan Broz <gmazyland@gmail.com>
Cc:     Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Herbert Xu <herbert@gondor.apana.org.au>
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On Thu, 21 Jan 2021 at 19:05, Eric Biggers <ebiggers@kernel.org> wrote:
>
> On Thu, Jan 21, 2021 at 02:07:33PM +0100, Ard Biesheuvel wrote:
> > Salsa20 is not used anywhere in the kernel, is not suitable for disk
> > encryption, and widely considered to have been superseded by ChaCha20.
> > So let's remove it.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> >  Documentation/admin-guide/device-mapper/dm-integrity.rst |    4 +-
> >  crypto/Kconfig                                           |   12 -
> >  crypto/Makefile                                          |    1 -
> >  crypto/salsa20_generic.c                                 |  212 ----
> >  crypto/tcrypt.c                                          |   11 +-
> >  crypto/testmgr.c                                         |    6 -
> >  crypto/testmgr.h                                         | 1162 --------------------
> >  7 files changed, 3 insertions(+), 1405 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/device-mapper/dm-integrity.rst b/Documentation/admin-guide/device-mapper/dm-integrity.rst
> > index 4e6f504474ac..d56112e2e354 100644
> > --- a/Documentation/admin-guide/device-mapper/dm-integrity.rst
> > +++ b/Documentation/admin-guide/device-mapper/dm-integrity.rst
> > @@ -143,8 +143,8 @@ recalculate
> >  journal_crypt:algorithm(:key)        (the key is optional)
> >       Encrypt the journal using given algorithm to make sure that the
> >       attacker can't read the journal. You can use a block cipher here
> > -     (such as "cbc(aes)") or a stream cipher (for example "chacha20",
> > -     "salsa20" or "ctr(aes)").
> > +     (such as "cbc(aes)") or a stream cipher (for example "chacha20"
> > +     or "ctr(aes)").
>
> You should check with the dm-integrity maintainers how likely it is that people
> are using salsa20 with dm-integrity.  It's possible that people are using it,
> especially since the documentation says that dm-integrity can use a stream
> cipher and specifically gives salsa20 as an example.
>

Good point - cc'ed them now.