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-rw-r--r--src/field_5x52_impl.h82
1 files changed, 56 insertions, 26 deletions
diff --git a/src/field_5x52_impl.h b/src/field_5x52_impl.h
index 4db9e6f5ff..2f9c8704a8 100644
--- a/src/field_5x52_impl.h
+++ b/src/field_5x52_impl.h
@@ -30,13 +30,11 @@
* output.
*/
-static void secp256k1_fe_inner_start(void) {}
-static void secp256k1_fe_inner_stop(void) {}
-
#ifdef VERIFY
static void secp256k1_fe_verify(const secp256k1_fe_t *a) {
const uint64_t *d = a->n;
int m = a->normalized ? 1 : 2 * a->magnitude, r = 1;
+ /* secp256k1 'p' value defined in "Standards for Efficient Cryptography" (SEC2) 2.7.1. */
r &= (d[0] <= 0xFFFFFFFFFFFFFULL * m);
r &= (d[1] <= 0xFFFFFFFFFFFFFULL * m);
r &= (d[2] <= 0xFFFFFFFFFFFFFULL * m);
@@ -62,8 +60,8 @@ static void secp256k1_fe_normalize(secp256k1_fe_t *r) {
uint64_t t0 = r->n[0], t1 = r->n[1], t2 = r->n[2], t3 = r->n[3], t4 = r->n[4];
/* Reduce t4 at the start so there will be at most a single carry from the first pass */
- uint64_t x = t4 >> 48; t4 &= 0x0FFFFFFFFFFFFULL;
uint64_t m;
+ uint64_t x = t4 >> 48; t4 &= 0x0FFFFFFFFFFFFULL;
/* The first pass ensures the magnitude is 1, ... */
t0 += x * 0x1000003D1ULL;
@@ -129,8 +127,8 @@ static void secp256k1_fe_normalize_var(secp256k1_fe_t *r) {
uint64_t t0 = r->n[0], t1 = r->n[1], t2 = r->n[2], t3 = r->n[3], t4 = r->n[4];
/* Reduce t4 at the start so there will be at most a single carry from the first pass */
- uint64_t x = t4 >> 48; t4 &= 0x0FFFFFFFFFFFFULL;
uint64_t m;
+ uint64_t x = t4 >> 48; t4 &= 0x0FFFFFFFFFFFFULL;
/* The first pass ensures the magnitude is 1, ... */
t0 += x * 0x1000003D1ULL;
@@ -172,12 +170,12 @@ static void secp256k1_fe_normalize_var(secp256k1_fe_t *r) {
static int secp256k1_fe_normalizes_to_zero(secp256k1_fe_t *r) {
uint64_t t0 = r->n[0], t1 = r->n[1], t2 = r->n[2], t3 = r->n[3], t4 = r->n[4];
- /* Reduce t4 at the start so there will be at most a single carry from the first pass */
- uint64_t x = t4 >> 48; t4 &= 0x0FFFFFFFFFFFFULL;
-
/* z0 tracks a possible raw value of 0, z1 tracks a possible raw value of P */
uint64_t z0, z1;
+ /* Reduce t4 at the start so there will be at most a single carry from the first pass */
+ uint64_t x = t4 >> 48; t4 &= 0x0FFFFFFFFFFFFULL;
+
/* The first pass ensures the magnitude is 1, ... */
t0 += x * 0x1000003D1ULL;
t1 += (t0 >> 52); t0 &= 0xFFFFFFFFFFFFFULL; z0 = t0; z1 = t0 ^ 0x1000003D0ULL;
@@ -193,22 +191,31 @@ static int secp256k1_fe_normalizes_to_zero(secp256k1_fe_t *r) {
}
static int secp256k1_fe_normalizes_to_zero_var(secp256k1_fe_t *r) {
- uint64_t t0 = r->n[0], t4 = r->n[4];
+ uint64_t t0, t1, t2, t3, t4;
+ uint64_t z0, z1;
+ uint64_t x;
+
+ t0 = r->n[0];
+ t4 = r->n[4];
/* Reduce t4 at the start so there will be at most a single carry from the first pass */
- uint64_t x = t4 >> 48;
+ x = t4 >> 48;
/* The first pass ensures the magnitude is 1, ... */
t0 += x * 0x1000003D1ULL;
/* z0 tracks a possible raw value of 0, z1 tracks a possible raw value of P */
- uint64_t z0 = t0 & 0xFFFFFFFFFFFFFULL, z1 = z0 ^ 0x1000003D0ULL;
+ z0 = t0 & 0xFFFFFFFFFFFFFULL;
+ z1 = z0 ^ 0x1000003D0ULL;
/* Fast return path should catch the majority of cases */
if ((z0 != 0ULL) & (z1 != 0xFFFFFFFFFFFFFULL))
return 0;
- uint64_t t1 = r->n[1], t2 = r->n[2], t3 = r->n[3];
+ t1 = r->n[1];
+ t2 = r->n[2];
+ t3 = r->n[3];
+
t4 &= 0x0FFFFFFFFFFFFULL;
t1 += (t0 >> 52); t0 = z0;
@@ -234,11 +241,11 @@ SECP256K1_INLINE static void secp256k1_fe_set_int(secp256k1_fe_t *r, int a) {
}
SECP256K1_INLINE static int secp256k1_fe_is_zero(const secp256k1_fe_t *a) {
+ const uint64_t *t = a->n;
#ifdef VERIFY
VERIFY_CHECK(a->normalized);
secp256k1_fe_verify(a);
#endif
- const uint64_t *t = a->n;
return (t[0] | t[1] | t[2] | t[3] | t[4]) == 0;
}
@@ -251,23 +258,25 @@ SECP256K1_INLINE static int secp256k1_fe_is_odd(const secp256k1_fe_t *a) {
}
SECP256K1_INLINE static void secp256k1_fe_clear(secp256k1_fe_t *a) {
+ int i;
#ifdef VERIFY
a->magnitude = 0;
a->normalized = 1;
#endif
- for (int i=0; i<5; i++) {
+ for (i=0; i<5; i++) {
a->n[i] = 0;
}
}
static int secp256k1_fe_cmp_var(const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
+ int i;
#ifdef VERIFY
VERIFY_CHECK(a->normalized);
VERIFY_CHECK(b->normalized);
secp256k1_fe_verify(a);
secp256k1_fe_verify(b);
#endif
- for (int i = 4; i >= 0; i--) {
+ for (i = 4; i >= 0; i--) {
if (a->n[i] > b->n[i]) return 1;
if (a->n[i] < b->n[i]) return -1;
}
@@ -275,9 +284,11 @@ static int secp256k1_fe_cmp_var(const secp256k1_fe_t *a, const secp256k1_fe_t *b
}
static int secp256k1_fe_set_b32(secp256k1_fe_t *r, const unsigned char *a) {
+ int i;
r->n[0] = r->n[1] = r->n[2] = r->n[3] = r->n[4] = 0;
- for (int i=0; i<32; i++) {
- for (int j=0; j<2; j++) {
+ for (i=0; i<32; i++) {
+ int j;
+ for (j=0; j<2; j++) {
int limb = (8*i+4*j)/52;
int shift = (8*i+4*j)%52;
r->n[limb] |= (uint64_t)((a[31-i] >> (4*j)) & 0xF) << shift;
@@ -296,13 +307,15 @@ static int secp256k1_fe_set_b32(secp256k1_fe_t *r, const unsigned char *a) {
/** Convert a field element to a 32-byte big endian value. Requires the input to be normalized */
static void secp256k1_fe_get_b32(unsigned char *r, const secp256k1_fe_t *a) {
+ int i;
#ifdef VERIFY
VERIFY_CHECK(a->normalized);
secp256k1_fe_verify(a);
#endif
- for (int i=0; i<32; i++) {
+ for (i=0; i<32; i++) {
+ int j;
int c = 0;
- for (int j=0; j<2; j++) {
+ for (j=0; j<2; j++) {
int limb = (8*i+4*j)/52;
int shift = (8*i+4*j)%52;
c |= ((a->n[limb] >> shift) & 0xF) << (4 * j);
@@ -386,18 +399,35 @@ static void secp256k1_fe_sqr(secp256k1_fe_t *r, const secp256k1_fe_t *a) {
#endif
}
-static void secp256k1_fe_cmov(secp256k1_fe_t *r, const secp256k1_fe_t *a, int flag) {
- uint64_t mask0 = flag + ~((uint64_t)0), mask1 = ~mask0;
+static SECP256K1_INLINE void secp256k1_fe_storage_cmov(secp256k1_fe_storage_t *r, const secp256k1_fe_storage_t *a, int flag) {
+ uint64_t mask0, mask1;
+ mask0 = flag + ~((uint64_t)0);
+ mask1 = ~mask0;
r->n[0] = (r->n[0] & mask0) | (a->n[0] & mask1);
r->n[1] = (r->n[1] & mask0) | (a->n[1] & mask1);
r->n[2] = (r->n[2] & mask0) | (a->n[2] & mask1);
r->n[3] = (r->n[3] & mask0) | (a->n[3] & mask1);
- r->n[4] = (r->n[4] & mask0) | (a->n[4] & mask1);
+}
+
+static void secp256k1_fe_to_storage(secp256k1_fe_storage_t *r, const secp256k1_fe_t *a) {
#ifdef VERIFY
- if (flag) {
- r->magnitude = a->magnitude;
- r->normalized = a->normalized;
- }
+ VERIFY_CHECK(a->normalized);
+#endif
+ r->n[0] = a->n[0] | a->n[1] << 52;
+ r->n[1] = a->n[1] >> 12 | a->n[2] << 40;
+ r->n[2] = a->n[2] >> 24 | a->n[3] << 28;
+ r->n[3] = a->n[3] >> 36 | a->n[4] << 16;
+}
+
+static SECP256K1_INLINE void secp256k1_fe_from_storage(secp256k1_fe_t *r, const secp256k1_fe_storage_t *a) {
+ r->n[0] = a->n[0] & 0xFFFFFFFFFFFFFULL;
+ r->n[1] = a->n[0] >> 52 | ((a->n[1] << 12) & 0xFFFFFFFFFFFFFULL);
+ r->n[2] = a->n[1] >> 40 | ((a->n[2] << 24) & 0xFFFFFFFFFFFFFULL);
+ r->n[3] = a->n[2] >> 28 | ((a->n[3] << 36) & 0xFFFFFFFFFFFFFULL);
+ r->n[4] = a->n[3] >> 16;
+#ifdef VERIFY
+ r->magnitude = 1;
+ r->normalized = 1;
#endif
}
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