linux-ext4 - Re: [PATCH] fscrypto: make XTS tweak initialization endian-independent

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Message-ID: <b38b2f9b-a598-f2ee-65d2-e89a08bc3129@nod.at>
Date:   Wed, 5 Oct 2016 23:18:37 +0200
From:   Richard Weinberger <richard@....at>
To:     Michael Halcrow <mhalcrow@...gle.com>
Cc:     David Gstir <david@...ma-star.at>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        Theodore Ts'o <tytso@....edu>, jaegeuk@...nel.org,
        Eric Biggers <ebiggers@...gle.com>,
        Anand Jain <anand.jain@...cle.com>,
        Tyler Hicks <tyhicks@...onical.com>
Subject: Re: [PATCH] fscrypto: make XTS tweak initialization
 endian-independent

Michael,

On 05.10.2016 23:11, Michael Halcrow wrote:
>>> In the meantime, to address the CBC thing, I'd want to understand what
>>> the hardware is doing exactly.  I wouldn't want the existence of code
>>> that supports CBC in fs/crypto to be interpreted as some sort of
>>> endorsement for using it rather than XTS (when unauthenticated
>>> encryption is for some reason the only viable option) for new storage
>>> encryption applications.
>>
>> The hardware offers AES-CBC, accessible via the kernel crypto API.
> 
> I presume your goal is to usually package up relatively large segments
> of data you'd like to chain together under one key/IV?

Yes. That's the plan.

> Else, for random-access block storage, I would like to get on idea on
> what the latency/throughput/power impact would be vs. just doing
> AES-XTS on the CPU.

Hopefully I can report some results soon. :-)

> Regardless, if you need IV generation in fs/crypto, you can use ESSIV
> from eCryptfs as an example.  Except you'll probably want to use
> SHA-256 instead of MD5, if only for the sake of hygiene.

Thanks for the pointer.

Thanks,
//richard
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