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SubjectRe: [RFC PATCH v2 07/12] crypto: arm/chacha - add XChaCha12 support
On 16 October 2018 at 01:54, Eric Biggers <ebiggers@kernel.org> wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> Now that the 32-bit ARM NEON implementation of ChaCha20 and XChaCha20
> has been refactored to support varying the number of rounds, add support
> for XChaCha12. This is identical to XChaCha20 except for the number of
> rounds, which is 12 instead of 20.
>
> XChaCha12 is faster than XChaCha20 but has a lower security margin,
> though still greater than AES-256's since the best known attacks make it
> through only 7 rounds. See the patch "crypto: chacha - add XChaCha12
> support" for more details about why we need XChaCha12 support.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---
> arch/arm/crypto/Kconfig | 2 +-
> arch/arm/crypto/chacha-neon-glue.c | 21 ++++++++++++++++++++-
> 2 files changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/crypto/Kconfig b/arch/arm/crypto/Kconfig
> index 0aa1471f27d2e..cc932d9bba561 100644
> --- a/arch/arm/crypto/Kconfig
> +++ b/arch/arm/crypto/Kconfig
> @@ -117,7 +117,7 @@ config CRYPTO_CRC32_ARM_CE
> select CRYPTO_HASH
>
> config CRYPTO_CHACHA20_NEON
> - tristate "NEON accelerated ChaCha20 stream cipher algorithms"
> + tristate "NEON accelerated ChaCha stream cipher algorithms"
> depends on KERNEL_MODE_NEON
> select CRYPTO_BLKCIPHER
> select CRYPTO_CHACHA20
> diff --git a/arch/arm/crypto/chacha-neon-glue.c b/arch/arm/crypto/chacha-neon-glue.c
> index b236af4889c61..0b1b238227707 100644
> --- a/arch/arm/crypto/chacha-neon-glue.c
> +++ b/arch/arm/crypto/chacha-neon-glue.c
> @@ -1,5 +1,6 @@
> /*
> - * ChaCha20 (RFC7539) and XChaCha20 stream ciphers, NEON accelerated
> + * ARM NEON accelerated ChaCha and XChaCha stream ciphers,
> + * including ChaCha20 (RFC7539)
> *
> * Copyright (C) 2016 Linaro, Ltd. <ard.biesheuvel@linaro.org>
> *
> @@ -160,6 +161,22 @@ static struct skcipher_alg algs[] = {
> .setkey = crypto_chacha20_setkey,
> .encrypt = xchacha_neon,
> .decrypt = xchacha_neon,
> + }, {
> + .base.cra_name = "xchacha12",
> + .base.cra_driver_name = "xchacha12-neon",
> + .base.cra_priority = 300,
> + .base.cra_blocksize = 1,
> + .base.cra_ctxsize = sizeof(struct chacha_ctx),
> + .base.cra_module = THIS_MODULE,
> +
> + .min_keysize = CHACHA_KEY_SIZE,
> + .max_keysize = CHACHA_KEY_SIZE,
> + .ivsize = XCHACHA_IV_SIZE,
> + .chunksize = CHACHA_BLOCK_SIZE,
> + .walksize = 4 * CHACHA_BLOCK_SIZE,
> + .setkey = crypto_chacha12_setkey,
> + .encrypt = xchacha_neon,
> + .decrypt = xchacha_neon,
> }
> };
>
> @@ -186,3 +203,5 @@ MODULE_ALIAS_CRYPTO("chacha20");
> MODULE_ALIAS_CRYPTO("chacha20-neon");
> MODULE_ALIAS_CRYPTO("xchacha20");
> MODULE_ALIAS_CRYPTO("xchacha20-neon");
> +MODULE_ALIAS_CRYPTO("xchacha12");
> +MODULE_ALIAS_CRYPTO("xchacha12-neon");
> --
> 2.19.1.331.ge82ca0e54c-goog
>

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