[email protected] (Niels Möller) writes:
> After some more thinking, I think this is the way to go. I'd like to
> propose the following plan:
>
> * Do a _salsa20_core, working with uint32_t. Consider it an internal
> function, and keep the interface open (maybe it should be able to do
> several blocks, maybe it should byteswap output words, etc).
[...]
> * Maybe have the C implementation salsa20_crypto also call _salsa20_core
> to do the main work. May require byteswapping in _salsa20_core output,
> to avoid a performance regression.
I tried extracting a _salsa20_core from salsa20_crypt. See patch below.
The function byteswaps the output words (if needed, i.e., on bigendian
machines).
On my machine (lowend, AMD E-350), the performance penalty is 4%, 12.25
cycles/byte before the change, 12.75 cycles/byte after. I think that's
ok if it can be shared with salsa20_core and scrypt.
(And on this machine there also appears to be no significant gain from
the current assembly implementation).
Regards,
/Niels
diff --git a/Makefile.in b/Makefile.in
index 9904be5..c0ca3ad 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -82,6 +82,7 @@ nettle_SOURCES = aes-decrypt-internal.c aes-decrypt.c \
md2.c md2-meta.c md4.c md4-meta.c \
md5.c md5-compress.c md5-compat.c md5-meta.c \
ripemd160.c ripemd160-compress.c ripemd160-meta.c \
+ salsa20-core-internal.c \
salsa20-crypt.c salsa20-set-key.c \
sha1.c sha1-compress.c sha1-meta.c \
sha256.c sha256-compress.c sha224-meta.c sha256-meta.c \
diff --git a/salsa20-core-internal.c b/salsa20-core-internal.c
new file mode 100644
index 0000000..2c1ae3c
--- /dev/null
+++ b/salsa20-core-internal.c
@@ -0,0 +1,85 @@
+/* salsa20-core-internal.c
+ *
+ * Internal interface to the Salsa20 core function.
+ */
+
+/* nettle, low-level cryptographics library
+ *
+ * Copyright (C) 2012 Simon Josefsson, Niels Möller
+ *
+ * The nettle library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ *
+ * The nettle library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the nettle library; see the file COPYING.LIB. If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02111-1301, USA.
+ */
+
+/* Based on:
+ salsa20-ref.c version 20051118
+ D. J. Bernstein
+ Public domain.
+*/
+
+#if HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <assert.h>
+#include <string.h>
+
+#include "salsa20.h"
+
+#include "macros.h"
+
+#ifdef WORDS_BIGENDIAN
+#define LE_SWAP32(v) \
+ ((ROTL32(8, v) & 0x00FF00FFUL) | \
+ (ROTL32(24, v) & 0xFF00FF00UL))
+#else
+#define LE_SWAP32(v) (v)
+#endif
+
+#define QROUND(x0, x1, x2, x3) do { \
+ x1 ^= ROTL32(7, x0 + x3); \
+ x2 ^= ROTL32(9, x1 + x0); \
+ x3 ^= ROTL32(13, x2 + x1); \
+ x0 ^= ROTL32(18, x3 + x2); \
+ } while(0)
+
+void
+_salsa20_core(uint32_t *dst, const uint32_t *src, unsigned rounds)
+{
+ uint32_t x[_SALSA20_INPUT_LENGTH];
+ unsigned i;
+
+ assert ( (rounds & 1) == 0);
+
+ memcpy (x, src, sizeof(x));
+ for (i = 0; i < rounds;i += 2)
+ {
+ QROUND(x[0], x[4], x[8], x[12]);
+ QROUND(x[5], x[9], x[13], x[1]);
+ QROUND(x[10], x[14], x[2], x[6]);
+ QROUND(x[15], x[3], x[7], x[11]);
+
+ QROUND(x[0], x[1], x[2], x[3]);
+ QROUND(x[5], x[6], x[7], x[4]);
+ QROUND(x[10], x[11], x[8], x[9]);
+ QROUND(x[15], x[12], x[13], x[14]);
+ }
+
+ for (i = 0; i < _SALSA20_INPUT_LENGTH; i++)
+ {
+ uint32_t t = x[i] + src[i];
+ dst[i] = LE_SWAP32 (t);
+ }
+}
diff --git a/salsa20-crypt.c b/salsa20-crypt.c
index eae3cea..b061b4b 100644
--- a/salsa20-crypt.c
+++ b/salsa20-crypt.c
@@ -40,21 +40,6 @@
#include "macros.h"
#include "memxor.h"
-#ifdef WORDS_BIGENDIAN
-#define LE_SWAP32(v) \
- ((ROTL32(8, v) & 0x00FF00FFUL) | \
- (ROTL32(24, v) & 0xFF00FF00UL))
-#else
-#define LE_SWAP32(v) (v)
-#endif
-
-#define QROUND(x0, x1, x2, x3) do { \
- x1 ^= ROTL32(7, x0 + x3); \
- x2 ^= ROTL32(9, x1 + x0); \
- x3 ^= ROTL32(13, x2 + x1); \
- x0 ^= ROTL32(18, x3 + x2); \
- } while(0)
-
void
salsa20_crypt(struct salsa20_ctx *ctx,
unsigned length,
@@ -67,26 +52,8 @@ salsa20_crypt(struct salsa20_ctx *ctx,
for (;;)
{
uint32_t x[_SALSA20_INPUT_LENGTH];
- int i;
- memcpy (x, ctx->input, sizeof(x));
- for (i = 0;i < 10;i ++)
- {
- QROUND(x[0], x[4], x[8], x[12]);
- QROUND(x[5], x[9], x[13], x[1]);
- QROUND(x[10], x[14], x[2], x[6]);
- QROUND(x[15], x[3], x[7], x[11]);
- QROUND(x[0], x[1], x[2], x[3]);
- QROUND(x[5], x[6], x[7], x[4]);
- QROUND(x[10], x[11], x[8], x[9]);
- QROUND(x[15], x[12], x[13], x[14]);
- }
-
- for (i = 0;i < _SALSA20_INPUT_LENGTH;++i)
- {
- uint32_t t = x[i] + ctx->input[i];
- x[i] = LE_SWAP32 (t);
- }
+ _salsa20_core (x, ctx->input, 20);
ctx->input[9] += (++ctx->input[8] == 0);
diff --git a/salsa20.h b/salsa20.h
index 7d47f52..d95d002 100644
--- a/salsa20.h
+++ b/salsa20.h
@@ -37,6 +37,7 @@ extern "C" {
#define salsa20_set_key nettle_salsa20_set_key
#define salsa20_set_iv nettle_salsa20_set_iv
#define salsa20_crypt nettle_salsa20_crypt
+#define _salsa20_core _nettle_salsa20_core
/* Minimum and maximum keysizes, and a reasonable default. In
* octets.*/
@@ -75,6 +76,9 @@ salsa20_crypt(struct salsa20_ctx *ctx,
unsigned length, uint8_t *dst,
const uint8_t *src);
+void
+_salsa20_core(uint32_t *dst, const uint32_t *src, unsigned rounds);
+
#ifdef __cplusplus
}
#endif
--
Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26.
Internet email is subject to wholesale government surveillance.
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