[dm-devel] [PATCH v3 6/6] crypto: arm64/aes - implement accelerated ESSIV/CBC mode

[Eric Biggers]

On Wed, Jun 19, 2019 at 06:29:21PM +0200, Ard Biesheuvel wrote:
> Add an accelerated version of the 'essiv(cbc(aes),aes,sha256)'
> skcipher, which is used by fscrypt, and in some cases, by dm-crypt.
> This avoids a separate call into the AES cipher for every invocation.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>

I'm not sure we should bother with this, since fscrypt normally uses AES-256-XTS
for contents encryption.  AES-128-CBC-ESSIV support was only added because
people wanted something that is fast on low-powered embedded devices with crypto
accelerators such as CAAM or CESA that don't support XTS.

In the case of Android, the CDD doesn't even allow AES-128-CBC-ESSIV with
file-based encryption (fscrypt).  It's still the default for "full disk
encryption" (which uses dm-crypt), but that's being deprecated.

So maybe dm-crypt users will want this, but I don't think it's very useful for
fscrypt.

- Eric