From: Eric Biggers <ebiggers@kernel.org>
To: linux-crypto@vger.kernel.org
Cc: linux-fscrypt@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Herbert Xu <herbert@gondor.apana.org.au>,
Paul Crowley <paulcrowley@google.com>,
Greg Kaiser <gkaiser@google.com>,
"Jason A . Donenfeld" <Jason@zx2c4.com>,
Samuel Neves <samuel.c.p.neves@gmail.com>,
Tomer Ashur <tomer.ashur@esat.kuleuven.be>
Subject: [RFC PATCH v3 01/15] crypto: chacha20-generic - add HChaCha20 library function
Date: Mon, 5 Nov 2018 15:25:12 -0800 [thread overview]
Message-ID: <20181105232526.173947-2-ebiggers@kernel.org> (raw)
In-Reply-To: <20181105232526.173947-1-ebiggers@kernel.org>
From: Eric Biggers <ebiggers@google.com>
Refactor the unkeyed permutation part of chacha20_block() into its own
function, then add hchacha20_block() which is the ChaCha equivalent of
HSalsa20 and is an intermediate step towards XChaCha20 (see
https://cr.yp.to/snuffle/xsalsa-20081128.pdf). HChaCha20 skips the
final addition of the initial state, and outputs only certain words of
the state. It should not be used for streaming directly.
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
include/crypto/chacha20.h | 2 ++
lib/chacha20.c | 50 ++++++++++++++++++++++++++++++++++-----
2 files changed, 46 insertions(+), 6 deletions(-)
diff --git a/include/crypto/chacha20.h b/include/crypto/chacha20.h
index f76302d99e2b..fbec4e6a8789 100644
--- a/include/crypto/chacha20.h
+++ b/include/crypto/chacha20.h
@@ -19,6 +19,8 @@ struct chacha20_ctx {
};
void chacha20_block(u32 *state, u8 *stream);
+void hchacha20_block(const u32 *in, u32 *out);
+
void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv);
int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keysize);
diff --git a/lib/chacha20.c b/lib/chacha20.c
index d907fec6a9ed..6a484e16171d 100644
--- a/lib/chacha20.c
+++ b/lib/chacha20.c
@@ -1,5 +1,5 @@
/*
- * ChaCha20 256-bit cipher algorithm, RFC7539
+ * The "hash function" used as the core of the ChaCha20 stream cipher (RFC7539)
*
* Copyright (C) 2015 Martin Willi
*
@@ -16,14 +16,10 @@
#include <asm/unaligned.h>
#include <crypto/chacha20.h>
-void chacha20_block(u32 *state, u8 *stream)
+static void chacha20_permute(u32 *x)
{
- u32 x[16];
int i;
- for (i = 0; i < ARRAY_SIZE(x); i++)
- x[i] = state[i];
-
for (i = 0; i < 20; i += 2) {
x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 16);
x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16);
@@ -65,6 +61,25 @@ void chacha20_block(u32 *state, u8 *stream)
x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7);
x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7);
}
+}
+
+/**
+ * chacha20_block - generate one keystream block and increment block counter
+ * @state: input state matrix (16 32-bit words)
+ * @stream: output keystream block (64 bytes)
+ *
+ * This is the ChaCha20 core, a function from 64-byte strings to 64-byte
+ * strings. The caller has already converted the endianness of the input. This
+ * function also handles incrementing the block counter in the input matrix.
+ */
+void chacha20_block(u32 *state, u8 *stream)
+{
+ u32 x[16];
+ int i;
+
+ memcpy(x, state, 64);
+
+ chacha20_permute(x);
for (i = 0; i < ARRAY_SIZE(x); i++)
put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]);
@@ -72,3 +87,26 @@ void chacha20_block(u32 *state, u8 *stream)
state[12]++;
}
EXPORT_SYMBOL(chacha20_block);
+
+/**
+ * hchacha20_block - abbreviated ChaCha20 core, for XChaCha20
+ * @in: input state matrix (16 32-bit words)
+ * @out: output (8 32-bit words)
+ *
+ * HChaCha20 is the ChaCha equivalent of HSalsa20 and is an intermediate step
+ * towards XChaCha20 (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf).
+ * HChaCha20 skips the final addition of the initial state, and outputs only
+ * certain words of the state. It should not be used for streaming directly.
+ */
+void hchacha20_block(const u32 *in, u32 *out)
+{
+ u32 x[16];
+
+ memcpy(x, in, 64);
+
+ chacha20_permute(x);
+
+ memcpy(&out[0], &x[0], 16);
+ memcpy(&out[4], &x[12], 16);
+}
+EXPORT_SYMBOL(hchacha20_block);
--
2.19.1.930.g4563a0d9d0-goog
next prev parent reply other threads:[~2018-11-05 23:27 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-05 23:25 [RFC PATCH v3 00/15] crypto: Adiantum support Eric Biggers
2018-11-05 23:25 ` Eric Biggers [this message]
2018-11-05 23:25 ` [RFC PATCH v3 02/15] crypto: chacha20-generic - don't unnecessarily use atomic walk Eric Biggers
2018-11-05 23:25 ` [RFC PATCH v3 03/15] crypto: chacha20-generic - add XChaCha20 support Eric Biggers
2018-11-05 23:25 ` [RFC PATCH v3 04/15] crypto: chacha20-generic - refactor to allow varying number of rounds Eric Biggers
2018-11-05 23:25 ` [RFC PATCH v3 05/15] crypto: chacha - add XChaCha12 support Eric Biggers
2018-11-05 23:25 ` [RFC PATCH v3 06/15] crypto: arm/chacha20 - limit the preemption-disabled section Eric Biggers
2018-11-05 23:25 ` [RFC PATCH v3 07/15] crypto: arm/chacha20 - add XChaCha20 support Eric Biggers
2018-11-06 12:41 ` Ard Biesheuvel
2018-11-05 23:25 ` [RFC PATCH v3 08/15] crypto: arm/chacha20 - refactor to allow varying number of rounds Eric Biggers
2018-11-06 12:46 ` Ard Biesheuvel
2018-11-05 23:25 ` [RFC PATCH v3 09/15] crypto: arm/chacha - add XChaCha12 support Eric Biggers
2018-11-05 23:25 ` [RFC PATCH v3 10/15] crypto: poly1305 - use structures for key and accumulator Eric Biggers
2018-11-06 14:28 ` Ard Biesheuvel
2018-11-12 18:58 ` Eric Biggers
2018-11-16 6:02 ` Herbert Xu
2018-11-17 0:17 ` Eric Biggers
2018-11-17 0:30 ` Ard Biesheuvel
2018-11-18 13:46 ` Jason A. Donenfeld
2018-11-19 5:24 ` [RFC PATCH] zinc chacha20 generic implementation using crypto API code Herbert Xu
2018-11-19 6:13 ` Jason A. Donenfeld
2018-11-19 6:22 ` Herbert Xu
2018-11-19 22:54 ` Eric Biggers
2018-11-19 23:15 ` Jason A. Donenfeld
2018-11-19 23:23 ` Eric Biggers
2018-11-19 23:31 ` Jason A. Donenfeld
2018-11-20 3:06 ` Herbert Xu
2018-11-20 3:08 ` Jason A. Donenfeld
2018-11-20 6:02 ` [RFC PATCH v2 0/4] Exporting existing crypto API code through zinc Herbert Xu
2018-11-20 6:04 ` [v2 PATCH 1/4] crypto: chacha20 - Export chacha20 functions without crypto API Herbert Xu
2018-11-20 6:04 ` [v2 PATCH 2/4] zinc: ChaCha20 generic C implementation and selftest Herbert Xu
2018-11-20 6:04 ` [v2 PATCH 3/4] zinc: Add x86 accelerated ChaCha20 Herbert Xu
2018-11-20 6:04 ` [v2 PATCH 4/4] zinc: ChaCha20 x86_64 implementation Herbert Xu
2018-11-20 10:32 ` [RFC PATCH v2 0/4] Exporting existing crypto API code through zinc Ard Biesheuvel
2018-11-20 14:18 ` Herbert Xu
2018-11-20 16:24 ` Jason A. Donenfeld
2018-11-20 18:51 ` Theodore Y. Ts'o
2018-11-21 7:55 ` Herbert Xu
2018-11-20 16:18 ` Jason A. Donenfeld
2018-11-21 6:01 ` Herbert Xu
2018-11-05 23:25 ` [RFC PATCH v3 11/15] crypto: poly1305 - add Poly1305 core API Eric Biggers
2018-11-05 23:25 ` [RFC PATCH v3 12/15] crypto: nhpoly1305 - add NHPoly1305 support Eric Biggers
2018-11-05 23:25 ` [RFC PATCH v3 13/15] crypto: arm/nhpoly1305 - add NEON-accelerated NHPoly1305 Eric Biggers
2018-11-05 23:25 ` [RFC PATCH v3 14/15] crypto: adiantum - add Adiantum support Eric Biggers
2018-11-05 23:25 ` [RFC PATCH v3 15/15] fscrypt: " Eric Biggers
2018-11-08 6:47 ` [RFC PATCH v3 00/15] crypto: " Martin Willi
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