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authorDenys Vlasenko2021-04-26 18:05:53 +0200
committerDenys Vlasenko2021-04-26 18:05:53 +0200
commit93b886f54bf85ca38f372ddd521f7c5bdbdc5d08 (patch)
tree5188e4160e4a9a5f50dacb2712a9ff109c5ef54e
parent6381f3d4f6d9ac111c2be7cfba041e8b7a28f9f9 (diff)
downloadbusybox-93b886f54bf85ca38f372ddd521f7c5bdbdc5d08.zip
busybox-93b886f54bf85ca38f372ddd521f7c5bdbdc5d08.tar.gz
tls: shrink sp_256_mont_inv_10
function old new delta sp_256_ecc_mulmod_10 1237 1251 +14 p256_mod_2 32 - -32 ------------------------------------------------------------------------------ (add/remove: 0/1 grow/shrink: 1/0 up/down: 14/-32) Total: -18 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--networking/tls_sp_c32.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/networking/tls_sp_c32.c b/networking/tls_sp_c32.c
index c71f716..97b2d3d 100644
--- a/networking/tls_sp_c32.c
+++ b/networking/tls_sp_c32.c
@@ -554,11 +554,18 @@ static void sp_256_mont_sqr_10(sp_digit* r, const sp_digit* a, const sp_digit* m
* r Inverse result.
* a Number to invert.
*/
+#if 0
/* Mod-2 for the P256 curve. */
static const uint32_t p256_mod_2[8] = {
0xfffffffd,0xffffffff,0xffffffff,0x00000000,
0x00000000,0x00000000,0x00000001,0xffffffff,
};
+//Bit pattern:
+//2 2 2 2 2 2 2 1...1
+//5 5 4 3 2 1 0 9...0 9...1
+//543210987654321098765432109876543210987654321098765432109876543210...09876543210...09876543210
+//111111111111111111111111111111110000000000000000000000000000000100...00000111111...11111111101
+#endif
static void sp_256_mont_inv_10(sp_digit* r, sp_digit* a)
{
sp_digit t[2*10]; //can be just [10]?
@@ -567,7 +574,8 @@ static void sp_256_mont_inv_10(sp_digit* r, sp_digit* a)
memcpy(t, a, sizeof(sp_digit) * 10);
for (i = 254; i >= 0; i--) {
sp_256_mont_sqr_10(t, t, p256_mod, p256_mp_mod);
- if (p256_mod_2[i / 32] & ((sp_digit)1 << (i % 32)))
+ /*if (p256_mod_2[i / 32] & ((sp_digit)1 << (i % 32)))*/
+ if (i >= 224 || i == 192 || (i <= 95 && i != 1))
sp_256_mont_mul_10(t, t, a, p256_mod, p256_mp_mod);
}
memcpy(r, t, sizeof(sp_digit) * 10);