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Subject: Re: [PATCH 0/4] KEYS: trusted: Introduce support for NXP CAAM-based
 trusted keys
To:     David Gstir <david@sigma-star.at>
Cc:     Jarkko Sakkinen <jarkko@kernel.org>,
        =?UTF-8?Q?Horia_Geant=c4=83?= <horia.geanta@nxp.com>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Aymen Sghaier <aymen.sghaier@nxp.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        James Bottomley <jejb@linux.ibm.com>,
        Jan Luebbe <j.luebbe@pengutronix.de>,
        Udit Agarwal <udit.agarwal@nxp.com>,
        Sumit Garg <sumit.garg@linaro.org>,
        Eric Biggers <ebiggers@kernel.org>,
        Franck LENORMAND <franck.lenormand@nxp.com>,
        Richard Weinberger <richard@nod.at>,
        James Morris <jmorris@namei.org>, linux-kernel@vger.kernel.org,
        David Howells <dhowells@redhat.com>,
        linux-security-module@vger.kernel.org, keyrings@vger.kernel.org,
        linux-crypto@vger.kernel.org, kernel@pengutronix.de,
        linux-integrity@vger.kernel.org,
        Steffen Trumtrar <s.trumtrar@pengutronix.de>,
        "Serge E. Hallyn" <serge@hallyn.com>
References: <cover.9fc9298fd9d63553491871d043a18affc2dbc8a8.1626885907.git-series.a.fatoum@pengutronix.de>
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 <74737543-4A73-49F8-92F7-F7FFE64A00DB@sigma-star.at>
From:   Ahmad Fatoum <a.fatoum@pengutronix.de>
Message-ID: <7f14dbb8-57a9-cbf5-a1f4-2ef7472da18d@pengutronix.de>
Date:   Fri, 20 Aug 2021 18:25:54 +0200
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Hello David,

On 10.08.21 13:28, David Gstir wrote:
> Hi Ahmad,
> 
>> On 09.08.2021, at 12:16, Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
> 
> [...]
> 
>> If it interests you, I described[2] my CAAM+ubifs+fscrypt use case in the
>> discussion thread on my fscrypt-trusted-keys v1. Jan, a colleague of mine, held a
>> talk[3] on the different solutions for authenticated and encrypted storage, which
>> you may want to check out.
>>
>> I'd really appreciate feedback here on the the CAAM parts of this series, so this can
>> eventually go mainline.
> 
> Since you mention the fscrypt trusted-keys use case:
> 
> I noticed that the key length for trusted-keys is limited to
> 256 - 1024bit keys. fscrypt does however also support keys
> with e.g. 128bit keys (AES-128-CBC-ESSIV, AES-128-CTS-CBC).
> AFAIK, CAAM and TEE key blobs would also support key lengths outside the 256 - 1024bit range.
> 
> Wouldn’t it make sense to align the supported key lengths?
> I.e. extend the range of supported key lengths for trusted keys.
> Or is there a specific reason why key lengths below 256bit are
> not supported by trusted-keys?

No idea. I would suggest staying clear about arguing in its favor though
until CAAM and DCP are merged. My parallel fscrypt endeavors seem to have
only diverted maintainer attention. ;-)

Cheers,
Ahmad

> 
> Cheers,
> David
> 
> 
> 


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