linux-kernel - Re: [RFC] crypto: xts - limit accepted key length

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Date:   Tue, 3 Mar 2020 13:35:51 +0100
From:   Milan Broz <gmazyland@...il.com>
To:     "Van Leeuwen, Pascal" <pvanleeuwen@...bus.com>,
        Andrei Botila <andrei.botila@....nxp.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
Cc:     "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] crypto: xts - limit accepted key length

On 02/03/2020 09:33, Van Leeuwen, Pascal wrote:
> Hmm ... in principle IEEE-1619 also defines XTS *only* for AES. So by that  same
> reasoning, you should also not allow any usage of XTS beyond AES. Yet it is
> actually being actively used(?) with other ciphers in the Linux kernel.
Just FYI - yes, it is actively used with other ciphers.

There is a lot of LUKS devices that use Serpent or Twofish with XTS mode.

The same for TrueCrypt/VeraCrypt, here sometimes it is used also in cipher chain
(both native binaries or cryptsetup code use dm-crypt with crypto API here).

XTS mode is designed for storage encryption only - and at least for disk encryption
I have never seen request for 192bit keys...

Milan