[git commit] tls: P256 code shrink
Denys Vlasenko
vda.linux at googlemail.com
Tue Oct 5 11:32:04 UTC 2021
commit: https://git.busybox.net/busybox/commit/?id=e730505034e9964176111c9e28b06c68cec1f4c0
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master
function old new delta
sp_256_to_bin_10 - 120 +120
sp_256_from_bin_10 - 119 +119
sp_256_proj_point_dbl_10 446 443 -3
curve_P256_compute_pubkey_and_premaster 191 186 -5
sp_256_point_from_bin2x32 62 50 -12
sp_256_to_bin 120 - -120
static.sp_256_from_bin 149 - -149
------------------------------------------------------------------------------
(add/remove: 2/2 grow/shrink: 0/3 up/down: 239/-289) Total: -50 bytes
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
networking/tls_sp_c32.c | 94 ++++++++++++++++++++++---------------------------
1 file changed, 42 insertions(+), 52 deletions(-)
diff --git a/networking/tls_sp_c32.c b/networking/tls_sp_c32.c
index 353dacdc4..9c92d0a14 100644
--- a/networking/tls_sp_c32.c
+++ b/networking/tls_sp_c32.c
@@ -80,13 +80,13 @@ static void sp_256_norm_10(sp_digit* a)
}
}
-/* Write r as big endian to byte aray.
+/* Write r as big endian to byte array.
* Fixed length number of bytes written: 32
*
* r A single precision integer.
* a Byte array.
*/
-static void sp_256_to_bin(sp_digit* r, uint8_t* a)
+static void sp_256_to_bin_10(sp_digit* r, uint8_t* a)
{
int i, j, s = 0, b;
@@ -112,33 +112,28 @@ static void sp_256_to_bin(sp_digit* r, uint8_t* a)
}
}
-/* Read big endian unsigned byte aray into r.
+/* Read big endian unsigned byte array into r.
*
* r A single precision integer.
* a Byte array.
* n Number of bytes in array to read.
*/
-static void sp_256_from_bin(sp_digit* r, int max, const uint8_t* a, int n)
+static void sp_256_from_bin_10(sp_digit* r, const uint8_t* a)
{
int i, j = 0, s = 0;
r[0] = 0;
- for (i = n-1; i >= 0; i--) {
+ for (i = 32 - 1; i >= 0; i--) {
r[j] |= ((sp_digit)a[i]) << s;
if (s >= 18) {
r[j] &= 0x3ffffff;
s = 26 - s;
- if (j + 1 >= max)
- break;
r[++j] = a[i] >> s;
s = 8 - s;
}
else
s += 8;
}
-
- for (j++; j < max; j++)
- r[j] = 0;
}
/* Convert a point of big-endian 32-byte x,y pair to type sp_point. */
@@ -146,11 +141,9 @@ static void sp_256_point_from_bin2x32(sp_point* p, const uint8_t *bin2x32)
{
memset(p, 0, sizeof(*p));
/*p->infinity = 0;*/
- sp_256_from_bin(p->x, 2 * 10, bin2x32, 32);
- sp_256_from_bin(p->y, 2 * 10, bin2x32 + 32, 32);
- //static const uint8_t one[1] = { 1 };
- //sp_256_from_bin(p->z, 2 * 10, one, 1);
- p->z[0] = 1;
+ sp_256_from_bin_10(p->x, bin2x32);
+ sp_256_from_bin_10(p->y, bin2x32 + 32);
+ p->z[0] = 1; /* p->z = 1 */
}
/* Compare a with b.
@@ -195,30 +188,6 @@ static void sp_256_sub_10(sp_digit* r, const sp_digit* a, const sp_digit* b)
r[i] = a[i] - b[i];
}
-/* Shift number left one bit. Bottom bit is lost. */
-static void sp_256_rshift1_10(sp_digit* r, sp_digit* a)
-{
- int i;
- for (i = 0; i < 9; i++)
- r[i] = ((a[i] >> 1) | (a[i + 1] << 25)) & 0x3ffffff;
- r[9] = a[9] >> 1;
-}
-
-/* Mul a by scalar b and add into r. (r += a * b) */
-static void sp_256_mul_add_10(sp_digit* r, const sp_digit* a, sp_digit b)
-{
- int64_t tb = b;
- int64_t t = 0;
- int i;
-
- for (i = 0; i < 10; i++) {
- t += (tb * a[i]) + r[i];
- r[i] = t & 0x3ffffff;
- t >>= 26;
- }
- r[10] += t;
-}
-
/* Multiply a and b into r. (r = a * b) */
static void sp_256_mul_10(sp_digit* r, const sp_digit* a, const sp_digit* b)
{
@@ -271,6 +240,15 @@ static void sp_256_sqr_10(sp_digit* r, const sp_digit* a)
r[0] = (sp_digit)(c >> 26);
}
+/* Shift number left one bit. Bottom bit is lost. */
+static void sp_256_rshift1_10(sp_digit* r, sp_digit* a)
+{
+ int i;
+ for (i = 0; i < 9; i++)
+ r[i] = ((a[i] >> 1) | (a[i + 1] << 25)) & 0x3ffffff;
+ r[9] = a[9] >> 1;
+}
+
/* Divide the number by 2 mod the modulus (prime). (r = a / 2 % m) */
static void sp_256_div2_10(sp_digit* r, const sp_digit* a, const sp_digit* m)
{
@@ -345,6 +323,20 @@ static void sp_256_mont_shift_10(sp_digit* r, const sp_digit* a)
memset(&r[10], 0, sizeof(*r) * 10);
}
+/* Mul a by scalar b and add into r. (r += a * b) */
+static void sp_256_mul_add_10(sp_digit* r, const sp_digit* a, sp_digit b)
+{
+ int64_t t = 0;
+ int i;
+
+ for (i = 0; i < 10; i++) {
+ t += ((int64_t)b * a[i]) + r[i];
+ r[i] = t & 0x3ffffff;
+ t >>= 26;
+ }
+ r[10] += t;
+}
+
/* Reduce the number back to 256 bits using Montgomery reduction.
*
* a A single precision number to reduce in place.
@@ -362,7 +354,7 @@ static void sp_256_mont_reduce_10(sp_digit* a, const sp_digit* m, sp_digit mp)
sp_256_mul_add_10(a+i, m, mu);
a[i+1] += a[i] >> 26;
}
- mu = (a[i] * mp) & 0x3fffffl;
+ mu = (a[i] * mp) & 0x03fffff;
sp_256_mul_add_10(a+i, m, mu);
a[i+1] += a[i] >> 26;
a[i] &= 0x3ffffff;
@@ -370,11 +362,11 @@ static void sp_256_mont_reduce_10(sp_digit* a, const sp_digit* m, sp_digit mp)
else {
for (i = 0; i < 9; i++) {
mu = a[i] & 0x3ffffff;
- sp_256_mul_add_10(a+i, p256_mod, mu);
+ sp_256_mul_add_10(a+i, m, mu);
a[i+1] += a[i] >> 26;
}
- mu = a[i] & 0x3fffffl;
- sp_256_mul_add_10(a+i, p256_mod, mu);
+ mu = a[i] & 0x03fffff;
+ sp_256_mul_add_10(a+i, m, mu);
a[i+1] += a[i] >> 26;
a[i] &= 0x3ffffff;
}
@@ -617,7 +609,6 @@ static void sp_256_map_10(sp_point* r, sp_point* p)
*/
static void sp_256_proj_point_dbl_10(sp_point* r, sp_point* p)
{
- sp_point tp;
sp_digit t1[2*10];
sp_digit t2[2*10];
@@ -625,10 +616,9 @@ static void sp_256_proj_point_dbl_10(sp_point* r, sp_point* p)
if (r != p)
*r = *p; /* struct copy */
- if (r->infinity) {
- /* If infinity, don't double (work on dummy value) */
- r = &tp;
- }
+ if (r->infinity) /* If infinity, don't double */
+ return;
+
/* T1 = Z * Z */
sp_256_mont_sqr_10(t1, r->z, p256_mod, p256_mp_mod);
/* Z = Y * Z */
@@ -848,7 +838,7 @@ static void sp_ecc_secret_gen_256(const sp_digit priv[10], const uint8_t *pub2x3
sp_256_ecc_mulmod_10(point, point, priv);
- sp_256_to_bin(point->x, out32);
+ sp_256_to_bin_10(point->x, out32);
dump_hex("out32: %s\n", out32, 32);
}
@@ -876,7 +866,7 @@ static void sp_256_ecc_gen_k_10(sp_digit k[10])
#if FIXED_SECRET
memset(buf, 0x77, sizeof(buf));
#endif
- sp_256_from_bin(k, 10, buf, sizeof(buf));
+ sp_256_from_bin_10(k, buf);
#if !SIMPLIFY
if (sp_256_cmp_10(k, p256_order2) < 0)
break;
@@ -901,8 +891,8 @@ static void sp_ecc_make_key_256(sp_digit privkey[10], uint8_t *pubkey)
sp_256_ecc_gen_k_10(privkey);
sp_256_ecc_mulmod_base_10(point, privkey);
- sp_256_to_bin(point->x, pubkey);
- sp_256_to_bin(point->y, pubkey + 32);
+ sp_256_to_bin_10(point->x, pubkey);
+ sp_256_to_bin_10(point->y, pubkey + 32);
memset(point, 0, sizeof(point)); //paranoia
}
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