Re: [PATCH v2 12/15] crypto: arm64/sm4 - add CE implementation for ESSIV mode

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Hi Eric,

On 10/25/22 1:20 PM, Eric Biggers wrote:
On Fri, Oct 21, 2022 at 10:47:14AM +0800, Tianjia Zhang wrote:
Hi Eric,

On 10/20/22 11:58 AM, Eric Biggers wrote:
On Tue, Oct 18, 2022 at 03:10:03PM +0800, Tianjia Zhang wrote:
This patch is a CE-optimized assembly implementation for ESSIV mode.
The assembly part is realized by reusing the CBC mode.

Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>

Is there still a use case for CBC-ESSIV mode these days, now that everyone is
using XTS instead?

- Eric

The mainstream is already using XTS, but CBC-ESSIV is still an optional
backup algorithm, especially in block crypto and fscrypto, I'm currently
working on supporting the SM4 algorithm for these subsystems.


The only reason that AES-CBC-ESSIV support was added to fs/crypto/ was because
someone had a low-power embedded device with a hardware crypto accelerator that
only supported AES-CBC.

Nothing like that is relevant here, as this is just a software implementation.

Please just don't include ESSIV.  There's no need to implement random useless
algorithms.  It could always be added later if a use case actually arises.

- Eric

Thanks for this information, I will remove the ESSIV code in the next
patch.

Best regards,
Tianjia



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