From b87ec212616765f920000b72d57b7a317e1a0c24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
Date: Wed, 27 Mar 2019 06:30:58 +0100
Subject: [PATCH] Rearrange cmac's block_mulx, make it closer to xts_shift.
* xts.c (xts_shift): Arrange with a single write to u64[1].
* cmac.c (block_mulx): Rewrite to work in the same way as
xts_shift, with 64-bit operations. XTS and CMAC use opposite
endianness, but otherwise, these two functions are identical.
---
ChangeLog | 7 +++++++
cmac.c | 27 ++++++++++++++++-----------
xts.c | 6 ++----
3 files changed, 25 insertions(+), 15 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 53896792..bb140378 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2019-03-27 Niels Möller <nisse@lysator.liu.se>
+
+ * xts.c (xts_shift): Arrange with a single write to u64[1].
+ * cmac.c (block_mulx): Rewrite to work in the same way as
+ xts_shift, with 64-bit operations. XTS and CMAC use opposite
+ endianness, but otherwise, these two functions are identical.
+
2019-03-24 Niels Möller <nisse@lysator.liu.se>
From Simo Sorce:
diff --git a/cmac.c b/cmac.c
index d08bd832..ed3b5eb8 100644
--- a/cmac.c
+++ b/cmac.c
@@ -47,22 +47,27 @@
#include "macros.h"
/* shift one and XOR with 0x87. */
+#if WORDS_BIGENDIAN
static void
block_mulx(union nettle_block16 *dst,
const union nettle_block16 *src)
{
- uint64_t b1 = READ_UINT64(src->b);
- uint64_t b2 = READ_UINT64(src->b+8);
-
- b1 = (b1 << 1) | (b2 >> 63);
- b2 <<= 1;
-
- if (src->b[0] & 0x80)
- b2 ^= 0x87;
-
- WRITE_UINT64(dst->b, b1);
- WRITE_UINT64(dst->b+8, b2);
+ uint64_t carry = src->u64[0] >> 63;
+ dst->u64[0] = (src->u64[0] << 1) | (src->u64[1] >> 63);
+ dst->u64[1] = (src->u64[1] << 1) ^ (0x87 & -carry);
+}
+#else /* !WORDS_BIGENDIAN */
+#define LE_SHIFT(x) ((((x) & 0x7f7f7f7f7f7f7f7f) << 1) | \
+ (((x) & 0x8080808080808080) >> 15))
+static void
+block_mulx(union nettle_block16 *dst,
+ const union nettle_block16 *src)
+{
+ uint64_t carry = (src->u64[0] & 0x80) >> 7;
+ dst->u64[0] = LE_SHIFT(src->u64[0]) | ((src->u64[1] & 0x80) << 49);
+ dst->u64[1] = LE_SHIFT(src->u64[1]) ^ (0x8700000000000000 & -carry);
}
+#endif /* !WORDS_BIGENDIAN */
void
cmac128_set_key(struct cmac128_ctx *ctx, const void *cipher,
diff --git a/xts.c b/xts.c
index ea2ceea9..6730b3ad 100644
--- a/xts.c
+++ b/xts.c
@@ -57,8 +57,7 @@ xts_shift(union nettle_block16 *dst,
{
uint64_t carry = (src->u64[1] & 0x80) >> 7;
dst->u64[1] = BE_SHIFT(src->u64[1]) | ((src->u64[0] & 0x80) << 49);
- dst->u64[0] = BE_SHIFT(src->u64[0]);
- dst->u64[0] ^= 0x8700000000000000 & -carry;
+ dst->u64[0] = BE_SHIFT(src->u64[0]) ^ (0x8700000000000000 & -carry);
}
#else /* !WORDS_BIGENDIAN */
static void
@@ -67,8 +66,7 @@ xts_shift(union nettle_block16 *dst,
{
uint64_t carry = src->u64[1] >> 63;
dst->u64[1] = (src->u64[1] << 1) | (src->u64[0] >> 63);
- dst->u64[0] = src->u64[0] << 1;
- dst->u64[0] ^= 0x87 & -carry;
+ dst->u64[0] = (src->u64[0] << 1) ^ (0x87 & -carry);
}
#endif /* !WORDS_BIGNDIAN */
--
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