From: Dmitry Eremin-Solenikov <dbarysh...@gmail.com>
Move GCM's block shift function to block-internal.h. This concludes
moving of all Galois mul-by-2 to single header.
Signed-off-by: Dmitry Eremin-Solenikov <dbarysh...@gmail.com>
---
block-internal.h | 30 +++++++++++++++++++++++++++++-
gcm.c | 30 ++----------------------------
2 files changed, 31 insertions(+), 29 deletions(-)
diff --git a/block-internal.h b/block-internal.h
index 8972d0ac2b5b..88e19be333c8 100644
--- a/block-internal.h
+++ b/block-internal.h
@@ -95,11 +95,15 @@ block8_xor_bytes (union nettle_block8 *r,
#define LSHIFT_ALIEN_UINT64(x) \
((((x) & UINT64_C(0x7f7f7f7f7f7f7f7f)) << 1) | \
(((x) & UINT64_C(0x8080808080808080)) >> 15))
+#define RSHIFT_ALIEN_UINT64(x) \
+ ((((x) & UINT64_C(0xfefefefefefefefe)) >> 1) | \
+ (((x) & UINT64_C(0x0001010101010101)) << 15))
/* Two typical defining polynoms */
#define BLOCK16_POLY (UINT64_C(0x87))
#define BLOCK8_POLY (UINT64_C(0x1b))
+#define GHASH_POLY (UINT64_C(0xE1))
/* Galois multiplications by 2:
* functions differ in shifting right or left, big- or little- endianness
@@ -133,6 +137,18 @@ block8_mulx_be (union nettle_block8 *dst,
dst->u64 = (src->u64 << 1) ^ (BLOCK8_POLY & -carry);
}
+
+static inline void
+block16_mulx_ghash (union nettle_block16 *r,
+ const union nettle_block16 *x)
+{
+ uint64_t mask;
+
+ /* Shift uses big-endian representation. */
+ mask = - (x->u64[1] & 1);
+ r->u64[1] = (x->u64[1] >> 1) | ((x->u64[0] & 1) << 63);
+ r->u64[0] = (x->u64[0] >> 1) ^ (mask & (GHASH_POLY << 56));
+}
#else /* !WORDS_BIGENDIAN */
static inline void
block16_mulx_be (union nettle_block16 *dst,
@@ -160,6 +176,18 @@ block8_mulx_be (union nettle_block8 *dst,
dst->u64 = LSHIFT_ALIEN_UINT64(src->u64) ^ ((BLOCK8_POLY << 56) & -carry);
}
-#endif /* !WORDS_BIGENDIAN */
+
+static inline void
+block16_mulx_ghash (union nettle_block16 *r,
+ const union nettle_block16 *x)
+{
+ uint64_t mask;
+
+ /* Shift uses big-endian representation. */
+ mask = - ((x->u64[1] >> 56) & 1);
+ r->u64[1] = RSHIFT_ALIEN_UINT64(x->u64[1]) | ((x->u64[0] >> 49) & 0x80);
+ r->u64[0] = RSHIFT_ALIEN_UINT64(x->u64[0]) ^ (mask & GHASH_POLY);
+}
+#endif /* ! WORDS_BIGENDIAN */
#endif /* NETTLE_BLOCK_INTERNAL_H_INCLUDED */
diff --git a/gcm.c b/gcm.c
index 4a04a0a10842..cf615daf18bd 100644
--- a/gcm.c
+++ b/gcm.c
@@ -55,32 +55,6 @@
#include "ctr-internal.h"
#include "block-internal.h"
-#define GHASH_POLYNOMIAL 0xE1UL
-
-/* Multiplication by 010...0; a big-endian shift right. If the bit
- shifted out is one, the defining polynomial is added to cancel it
- out. r == x is allowed. */
-static void
-gcm_gf_shift (union nettle_block16 *r, const union nettle_block16 *x)
-{
- uint64_t mask;
-
- /* Shift uses big-endian representation. */
-#if WORDS_BIGENDIAN
- mask = - (x->u64[1] & 1);
- r->u64[1] = (x->u64[1] >> 1) | ((x->u64[0] & 1) << 63);
- r->u64[0] = (x->u64[0] >> 1) ^ (mask & ((uint64_t) GHASH_POLYNOMIAL << 56));
-#else /* ! WORDS_BIGENDIAN */
-#define RSHIFT_WORD(x) \
- ((((x) & 0xfefefefefefefefeUL) >> 1) \
- | (((x) & 0x0001010101010101UL) << 15))
- mask = - ((x->u64[1] >> 56) & 1);
- r->u64[1] = RSHIFT_WORD(x->u64[1]) | ((x->u64[0] >> 49) & 0x80);
- r->u64[0] = RSHIFT_WORD(x->u64[0]) ^ (mask & GHASH_POLYNOMIAL);
-# undef RSHIFT_WORD
-#endif /* ! WORDS_BIGENDIAN */
-}
-
#if GCM_TABLE_BITS == 0
/* Sets x <- x * y mod r, using the plain bitwise algorithm from the
specification. y may be shorter than a full block, missing bytes
@@ -104,7 +78,7 @@ gcm_gf_mul (union nettle_block16 *x, const union
nettle_block16 *y)
if (b & 0x80)
block16_xor(&Z, &V);
- gcm_gf_shift(&V, &V);
+ block16_mulx_ghash(&V, &V);
}
}
memcpy (x->b, Z.b, sizeof(Z));
@@ -275,7 +249,7 @@ gcm_set_key(struct gcm_key *key,
/* Algorithm 3 from the gcm paper. First do powers of two, then do
the rest by adding. */
while (i /= 2)
- gcm_gf_shift(&key->h[i], &key->h[2*i]);
+ block16_mulx_ghash(&key->h[i], &key->h[2*i]);
for (i = 2; i < 1<<GCM_TABLE_BITS; i *= 2)
{
unsigned j;
--
2.23.0.rc1
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