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From:   Gilad Ben-Yossef <gilad@benyossef.com>
Date:   Sat, 24 Jul 2021 12:42:20 +0300
Message-ID: <CAOtvUMfwbBr44qOCma4RaH_RoC35x00N=O1Ejaxc+5EPGY8rUw@mail.gmail.com>
Subject: Re: Extending CRYPTO_ALG_OPTIONAL_KEY for cipher algorithms
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     Thara Gopinath <thara.gopinath@linaro.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>
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On Fri, Jul 23, 2021 at 7:20 PM Eric Biggers <ebiggers@kernel.org> wrote:
>
> On Fri, Jul 23, 2021 at 06:13:50AM -0400, Thara Gopinath wrote:
> > Hi
> >
> > I have a requirement where the keys for the crypto cipher algorithms ar=
e
> > already programmed in the h/w pipes/channels and thus the ->encrypt()
> > and ->decrypt() can be called without set_key being called first.
> > I see that CRYPTO_ALG_OPTIONAL_KEY has been added to take care of
> > such requirements for CRC-32. My question is can the usage of this flag
> > be extended for cipher and other crypto algorithms as well. Can setting=
 of
> > this flag indicate that the algorithm can be used without calling set_k=
ey
> > first and then the individual drivers can handle cases where
> > both h/w keys and s/w keys need to be supported.
>
> CRYPTO_ALG_OPTIONAL_KEY isn't meant for this use case, but rather for alg=
orithms
> that have both keyed and unkeyed versions such as BLAKE2b and BLAKE2s, an=
d also
> for algorithms where the "key" isn't actually a key but rather is an init=
ial
> value that has a default value, such as CRC-32 and xxHash.
>
> It appears that that the case you're asking about is handled by using a
> different algorithm name, e.g. see the "paes" algorithms in
> drivers/crypto/ccree/cc_cipher.c.

Yeap, seems like another use case for "protected keys" like CryptoCell
and the IBM mainframe.
I gave a talk about this you might find useful -
https://www.youtube.com/watch?v=3DGbcpwUBFGDw

Feel free to contact me if you have questions.

Cheers,
Gilad

--=20
Gilad Ben-Yossef
Chief Coffee Drinker

values of =CE=B2 will give rise to dom!