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From: Milan Broz <gmazyland@gmail.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>, linux-crypto@vger.kernel.org
Cc: herbert@gondor.apana.org.au, ebiggers@kernel.org, agk@redhat.com,
	snitzer@redhat.com, dm-devel@redhat.com
Subject: Re: [RFC PATCH v2] md/dm-crypt - reuse eboiv skcipher for IV generation
Date: Wed, 7 Aug 2019 10:08:58 +0200
Message-ID: <c83ec561-4359-3f38-3da3-65f9f18c1822@gmail.com> (raw)
In-Reply-To: <20190807055022.15551-1-ard.biesheuvel@linaro.org>

On 07/08/2019 07:50, Ard Biesheuvel wrote:
> Instead of instantiating a separate cipher to perform the encryption
> needed to produce the IV, reuse the skcipher used for the block data
> and invoke it one additional time for each block to encrypt a zero
> vector and use the output as the IV.
> 
> For CBC mode, this is equivalent to using the bare block cipher, but
> without the risk of ending up with a non-time invariant implementation
> of AES when the skcipher itself is time variant (e.g., arm64 without
> Crypto Extensions has a NEON based time invariant implementation of
> cbc(aes) but no time invariant implementation of the core cipher other
> than aes-ti, which is not enabled by default)
> 
> This approach is a compromise between dm-crypt API flexibility and
> reducing dependence on parts of the crypto API that should not usually
> be exposed to other subsystems, such as the bare cipher API.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Yes, this is a good idea, I'll test it. Thanks!

Milan

  parent reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-07  5:50 Ard Biesheuvel
2019-08-07  7:28 ` Pascal Van Leeuwen
2019-08-07 13:17   ` Ard Biesheuvel
2019-08-07 13:52     ` Pascal Van Leeuwen
2019-08-07 15:39       ` Ard Biesheuvel
2019-08-07 16:14         ` Pascal Van Leeuwen
2019-08-07 16:50           ` Ard Biesheuvel
2019-08-07 20:22             ` Pascal Van Leeuwen
2019-08-08  8:30           ` Eric Biggers
2019-08-08  9:31             ` Pascal Van Leeuwen
2019-08-08 12:52               ` Milan Broz
2019-08-08 13:23                 ` Pascal Van Leeuwen
2019-08-08 17:15                   ` Eric Biggers
2019-08-09  9:17                     ` Pascal Van Leeuwen
2019-08-09 17:17                       ` Eric Biggers
2019-08-09 20:29                         ` Pascal Van Leeuwen
2019-08-09 20:56                           ` Eric Biggers
2019-08-09 21:33                             ` Pascal Van Leeuwen
2019-08-09 22:04                               ` Eric Biggers
2019-08-09 23:01                                 ` Pascal Van Leeuwen
2019-08-07  8:08 ` Milan Broz [this message]
2019-08-08 11:53 ` Milan Broz
2019-08-09 18:52   ` Ard Biesheuvel

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