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Date: Tue, 5 Dec 2023 16:41:12 +0800
From: Herbert Xu <herbert@gondor.apana.org.au>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH 4/8] crypto: skcipher - Add lskcipher
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On Thu, Sep 21, 2023 at 08:10:30PM -0700, Eric Biggers wrote:
> 
> Yes, wide-block modes such as Adiantum and HCTR2 require multiple passes over
> the data.  As do SIV modes such as AES-GCM-SIV (though AES-GCM-SIV isn't yet
> supported by the kernel, and it would be an "aead", not an "skcipher").

Right, AEAD algorithms have never supported incremental processing,
as one of the first algorithms CCM required two-pass processing.

We could support incremental processing if we really wanted to.  It
would require a model where the user passes the data to the API twice
(or more if future algorithms requires so).  However, I see no
pressing need for this so I'm happy with just marking such algorithms
as unsupported with algif_skcipher for now.  There is also an
alternative of adding an AEAD-like mode fo algif_skcipher for these
algorithms but again I don't see the need to do this.

As such I'm going to add a field to indicate that adiantum and hctr2
cannot be used by algif_skcipher.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt