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Subject[RFC PATCH 7/9] crypto: arm/chacha - add XChaCha12 support
Date
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 reduced from 20 to 12.

As I explained in more detail in the patch which added XChaCha12 to the
generic code, "crypto: chacha - add XChaCha12 support", we'd prefer to
use XChaCha20, but unfortunately it is not fast enough for our use case.
Thus, we must settle for a reduced-round variant. See that patch for a
more detailed explanation.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
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 896dcf142719..75c613413e31 100644
--- a/arch/arm/crypto/Kconfig
+++ b/arch/arm/crypto/Kconfig
@@ -116,7 +116,7 @@ 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 b236af4889c6..0b1b23822770 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");
--
2.18.0.597.ga71716f1ad-goog
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