From: Eric Biggers <ebiggers3@gmail.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: linux-crypto@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
herbert@gondor.apana.org.au
Subject: Re: [RFC PATCH v2 4/4] crypto: aes - add generic time invariant AES for CTR/CCM/GCM
Date: Wed, 1 Feb 2017 23:38:24 -0800 [thread overview]
Message-ID: <20170202073824.GC582@zzz> (raw)
In-Reply-To: <1485646413-17491-5-git-send-email-ard.biesheuvel@linaro.org>
Hi Ard,
On Sat, Jan 28, 2017 at 11:33:33PM +0000, Ard Biesheuvel wrote:
>
> Note that this only implements AES encryption, which is all we need
> for CTR and CBC-MAC. AES decryption can easily be implemented in a
> similar way, but is significantly more costly.
Is the expectation of decryption being more costly the only reason why "aes-ti"
couldn't be a "cipher" algorithm, allowing it to automatically be used by the
existing templates for CTR, CBC-MAC, CBC, ECB, XTS, CMAC, etc.? It doesn't seem
to do anything expensive on a per-block basis like loading SSE registers, so it
seems it would fit better as a "cipher" algorithm if at all possible. Then
there would be no need to implement all these modes yet again.
Also, what would be the feasibility of simply replacing aes-generic with the
time-invariant implementation, rather than offering two implementations and
requiring users to choose one, usually without the needed expertise?
> +
> +/*
> + * Emit the sbox as __weak with external linkage to prevent the compiler
> + * from doing constant folding on sbox references involving fixed indexes.
> + */
> +__weak const u8 __cacheline_aligned __aesti_sbox[] = {
Did you consider marking it 'volatile' instead?
> +static int aesti_set_key(struct aes_ti_ctx *ctx, const u8 *in_key,
> + unsigned int key_len)
> +{
> + struct crypto_aes_ctx rk;
> + int err;
> +
> + err = crypto_aes_expand_key(&rk, in_key, key_len);
> + if (err)
> + return err;
crypto_aes_expand_key() assumes that the key is u32-aligned; I don't think
that's guaranteed here.
Eric
next prev parent reply other threads:[~2017-02-02 7:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-28 23:33 [PATCH v2 0/4] crypto: time invariant AES for CCM (and GCM/CTR) Ard Biesheuvel
2017-01-28 23:33 ` [PATCH v2 1/4] crypto: testmgr - add test cases for cbcmac(aes) Ard Biesheuvel
2017-01-28 23:33 ` [PATCH v2 2/4] crypto: ccm - switch to separate cbcmac driver Ard Biesheuvel
2017-02-02 18:56 ` Ard Biesheuvel
2017-01-28 23:33 ` [PATCH v2 3/4] crypto: arm64/aes - add NEON and Crypto Extension CBC-MAC driver Ard Biesheuvel
2017-01-28 23:33 ` [RFC PATCH v2 4/4] crypto: aes - add generic time invariant AES for CTR/CCM/GCM Ard Biesheuvel
2017-02-02 7:38 ` Eric Biggers [this message]
2017-02-02 7:48 ` Ard Biesheuvel
2017-02-02 7:55 ` Ard Biesheuvel
2017-01-31 18:30 ` [PATCH v2 0/4] crypto: time invariant AES for CCM (and GCM/CTR) Ard Biesheuvel
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