[git commit] tls: shrink p256_base more

Denys Vlasenko vda.linux at googlemail.com
Tue Apr 27 10:24:21 UTC 2021


commit: https://git.busybox.net/busybox/commit/?id=48a18d15dfbfa41d137802e811a3abdfef012ac8
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master

function                                             old     new   delta
static.p256_base_bin                                   -      64     +64
sp_256_point_from_bin2x32                              -      62     +62
static.base_y                                         40       -     -40
static.base_x                                         40       -     -40
curve_P256_compute_pubkey_and_premaster              291     194     -97
------------------------------------------------------------------------------
(add/remove: 2/2 grow/shrink: 0/1 up/down: 126/-177)          Total: -51 bytes

Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 networking/tls_sp_c32.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/networking/tls_sp_c32.c b/networking/tls_sp_c32.c
index 64c53b006..f9c66b186 100644
--- a/networking/tls_sp_c32.c
+++ b/networking/tls_sp_c32.c
@@ -790,19 +790,16 @@ static void sp_256_ecc_mulmod_base_10(sp_point* r, sp_digit* k /*, int map*/)
 	 * don't have "static const sp_point p256_base = {...}",
 	 * it would have more zeros than data.
 	 */
-	static const sp_digit base_x[] = {
-		0x098c296,0x04e5176,0x33a0f4a,0x204b7ac,0x277037d,0x0e9103c,0x3ce6e56,0x1091fe2,0x1f2e12c,0x01ac5f4
-	};
-	static const sp_digit base_y[] = {
-		0x3bf51f5,0x1901a0d,0x1ececbb,0x15dacc5,0x22bce33,0x303e785,0x27eb4a7,0x1fe6e3b,0x2e2fe1a,0x013f8d0
+	static const uint8_t p256_base_bin[] = {
+		/* x (big-endian) */
+		0x6b,0x17,0xd1,0xf2,0xe1,0x2c,0x42,0x47,0xf8,0xbc,0xe6,0xe5,0x63,0xa4,0x40,0xf2,0x77,0x03,0x7d,0x81,0x2d,0xeb,0x33,0xa0,0xf4,0xa1,0x39,0x45,0xd8,0x98,0xc2,0x96,
+		/* y */
+		0x4f,0xe3,0x42,0xe2,0xfe,0x1a,0x7f,0x9b,0x8e,0xe7,0xeb,0x4a,0x7c,0x0f,0x9e,0x16,0x2b,0xce,0x33,0x57,0x6b,0x31,0x5e,0xce,0xcb,0xb6,0x40,0x68,0x37,0xbf,0x51,0xf5,
+		/* z will be set to 0, infinity flag to "false" */
 	};
 	sp_point p256_base;
 
-	memset(&p256_base, 0, sizeof(p256_base));
-	memcpy(p256_base.x, base_x, sizeof(base_x));
-	memcpy(p256_base.y, base_y, sizeof(base_y));
-	p256_base.z[0] = 1;
-	/*p256_base.infinity = 0;*/
+	sp_256_point_from_bin2x32(&p256_base, p256_base_bin);
 
 	sp_256_ecc_mulmod_10(r, &p256_base, k /*, map*/);
 }


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