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>,
Michael Halcrow <mhalcrow@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 v2 01/12] crypto: chacha20-generic - add HChaCha20 library function
Date: Mon, 15 Oct 2018 10:54:13 -0700 [thread overview]
Message-ID: <20181015175424.97147-2-ebiggers@kernel.org> (raw)
In-Reply-To: <20181015175424.97147-1-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.
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 f76302d99e2be..fbec4e6a87890 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 d907fec6a9ed1..6a484e16171d1 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);
--
2.19.1.331.ge82ca0e54c-goog
next prev parent reply other threads:[~2018-10-15 17:56 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-15 17:54 [RFC PATCH v2 00/12] crypto: Adiantum support Eric Biggers
2018-10-15 17:54 ` Eric Biggers [this message]
2018-10-19 14:13 ` [RFC PATCH v2 01/12] crypto: chacha20-generic - add HChaCha20 library function Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 02/12] crypto: chacha20-generic - add XChaCha20 support Eric Biggers
2018-10-19 14:24 ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 03/12] crypto: chacha20-generic - refactor to allow varying number of rounds Eric Biggers
2018-10-19 14:25 ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 04/12] crypto: chacha - add XChaCha12 support Eric Biggers
2018-10-19 14:34 ` Ard Biesheuvel
2018-10-19 18:28 ` Eric Biggers
2018-10-15 17:54 ` [RFC PATCH v2 05/12] crypto: arm/chacha20 - add XChaCha20 support Eric Biggers
2018-10-20 2:29 ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 06/12] crypto: arm/chacha20 - refactor to allow varying number of rounds Eric Biggers
2018-10-20 3:35 ` Ard Biesheuvel
2018-10-20 5:26 ` Eric Biggers
2018-10-15 17:54 ` [RFC PATCH v2 07/12] crypto: arm/chacha - add XChaCha12 support Eric Biggers
2018-10-20 3:36 ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 08/12] crypto: poly1305 - add Poly1305 core API Eric Biggers
2018-10-20 3:45 ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 09/12] crypto: nhpoly1305 - add NHPoly1305 support Eric Biggers
2018-10-20 4:00 ` Ard Biesheuvel
2018-10-20 5:38 ` Eric Biggers
2018-10-20 15:06 ` Ard Biesheuvel
2018-10-22 18:42 ` Eric Biggers
2018-10-22 22:25 ` Ard Biesheuvel
2018-10-22 22:40 ` Eric Biggers
2018-10-22 22:43 ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 10/12] crypto: arm/nhpoly1305 - add NEON-accelerated NHPoly1305 Eric Biggers
2018-10-20 4:12 ` Ard Biesheuvel
2018-10-20 5:51 ` Eric Biggers
2018-10-20 15:00 ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 11/12] crypto: adiantum - add Adiantum support Eric Biggers
2018-10-20 4:17 ` Ard Biesheuvel
2018-10-20 7:12 ` Eric Biggers
2018-10-23 10:40 ` Ard Biesheuvel
2018-10-24 22:06 ` Eric Biggers
2018-10-30 8:17 ` Herbert Xu
2018-10-15 17:54 ` [RFC PATCH v2 12/12] fscrypt: " Eric Biggers
2018-10-19 15:58 ` [RFC PATCH v2 00/12] crypto: " Jason A. Donenfeld
2018-10-19 18:19 ` Paul Crowley
2018-10-20 3:24 ` Ard Biesheuvel
2018-10-20 5:22 ` Eric Biggers
[not found] ` <2395454e-a0dc-408f-4138-9d15ab5f20b8@esat.kuleuven.be>
2018-10-22 11:20 ` Tomer Ashur
2018-10-19 19:04 ` Eric Biggers
2018-10-20 10:26 ` Milan Broz
2018-10-20 13:47 ` Jason A. Donenfeld
2018-11-16 21:52 ` Eric Biggers
2018-11-17 10:29 ` Milan Broz
2018-11-19 19:28 ` Eric Biggers
2018-11-19 20:05 ` Milan Broz
2018-11-19 20:30 ` Jason A. Donenfeld
2018-10-21 22:23 ` Eric Biggers
2018-10-21 22:51 ` Jason A. Donenfeld
2018-10-22 17:17 ` Paul Crowley
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181015175424.97147-2-ebiggers@kernel.org \
--to=ebiggers@kernel.org \
--cc=Jason@zx2c4.com \
--cc=gkaiser@google.com \
--cc=herbert@gondor.apana.org.au \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-fscrypt@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mhalcrow@google.com \
--cc=paulcrowley@google.com \
--cc=samuel.c.p.neves@gmail.com \
--cc=tomer.ashur@esat.kuleuven.be \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).