linux-kernel - Re: [RFC PATCH v2] crypto: Add IV generation algorithms

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Date:   Wed, 14 Dec 2016 11:39:52 +0530
From:   Binoy Jayan <binoy.jayan@...aro.org>
To:     Milan Broz <gmazyland@...il.com>
Cc:     Oded <oded.golombek@....com>, Ofir <Ofir.Drang@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        Shaohua Li <shli@...nel.org>, linux-raid@...r.kernel.org,
        Rajendra <rnayak@...eaurora.org>
Subject: Re: [RFC PATCH v2] crypto: Add IV generation algorithms

Hi Milan,

Thank you for the reply.

On 13 December 2016 at 15:31, Milan Broz <gmazyland@...il.com> wrote:

> I really do not think the disk encryption key management should be moved
> outside of dm-crypt. We cannot then change key structure later easily.

Yes, I agree. but the key selection based on sector number restricts the
option of having a larger block size used for encryption.

>> +     unsigned int key_size;
>> +     unsigned int key_extra_size;
>> +     unsigned int key_parts;      /* independent parts in key buffer */
>
> ^^^ these key sizes you probably mean by key management.

Yes, I mean splitting the keys into subkeys based on the keycount
parameter (as mentioned below) to the dm-crypt.

cipher[:keycount]-mode-iv:ivopts
aes:2-cbc-essiv:sha256

> It is based on way how the key is currently sent into kernel
> (one hexa string in ioctl that needs to be split) and have to be changed in future.

-Binoy