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Merge pull request #154

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49ee0db Add _normalizes_to_zero_var variant (Peter Dettman)
eed599d Add _fe_normalizes_to_zero method (Peter Dettman)
d7174ed Weak normalization for secp256k1_fe_equal (Pieter Wuille)
0295f0a weak normalization (Pieter Wuille)
This commit is contained in:
Pieter Wuille 2014-12-22 22:02:54 +01:00
commit d57cae9473
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GPG Key ID: 57896D2FF8F0B657
9 changed files with 228 additions and 76 deletions
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2
src/ecmult_gen_impl.h
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@ -73,7 +73,7 @@ static void secp256k1_ecmult_gen_start(void) {
secp256k1_gej_double_var(&numsbase, &numsbase);
if (j == 62) {
/* In the last iteration, numsbase is (1 - 2^j) * nums instead. */
secp256k1_gej_neg_var(&numsbase, &numsbase);
secp256k1_gej_neg(&numsbase, &numsbase);
secp256k1_gej_add_var(&numsbase, &numsbase, &nums_gej);
}
}

4
src/ecmult_impl.h
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@ -70,8 +70,8 @@ static void secp256k1_ecmult_table_precomp_ge_var(secp256k1_ge_t *pre, const sec
(neg)((r), &(pre)[(-(n)-1)/2]); \
} while(0)
#define ECMULT_TABLE_GET_GEJ(r,pre,n,w) ECMULT_TABLE_GET((r),(pre),(n),(w),secp256k1_gej_neg_var)
#define ECMULT_TABLE_GET_GE(r,pre,n,w) ECMULT_TABLE_GET((r),(pre),(n),(w),secp256k1_ge_neg_var)
#define ECMULT_TABLE_GET_GEJ(r,pre,n,w) ECMULT_TABLE_GET((r),(pre),(n),(w),secp256k1_gej_neg)
#define ECMULT_TABLE_GET_GE(r,pre,n,w) ECMULT_TABLE_GET((r),(pre),(n),(w),secp256k1_ge_neg)
typedef struct {
/* For accelerating the computation of a*P + b*G: */

15
src/field.h
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@ -48,9 +48,20 @@ static void secp256k1_fe_stop(void);
/** Normalize a field element. */
static void secp256k1_fe_normalize(secp256k1_fe_t *r);
/** Weakly normalize a field element: reduce it magnitude to 1, but don't fully normalize. */
static void secp256k1_fe_normalize_weak(secp256k1_fe_t *r);
/** Normalize a field element, without constant-time guarantee. */
static void secp256k1_fe_normalize_var(secp256k1_fe_t *r);
/** Verify whether a field element represents zero i.e. would normalize to a zero value. The field
* implementation may optionally normalize the input, but this should not be relied upon. */
static int secp256k1_fe_normalizes_to_zero(secp256k1_fe_t *r);
/** Verify whether a field element represents zero i.e. would normalize to a zero value. The field
* implementation may optionally normalize the input, but this should not be relied upon. */
static int secp256k1_fe_normalizes_to_zero_var(secp256k1_fe_t *r);
/** Set a field element equal to a small integer. Resulting field element is normalized. */
static void secp256k1_fe_set_int(secp256k1_fe_t *r, int a);
@ -60,8 +71,8 @@ static int secp256k1_fe_is_zero(const secp256k1_fe_t *a);
/** Check the "oddness" of a field element. Requires the input to be normalized. */
static int secp256k1_fe_is_odd(const secp256k1_fe_t *a);
/** Compare two field elements. Requires both inputs to be normalized */
static int secp256k1_fe_equal(const secp256k1_fe_t *a, const secp256k1_fe_t *b);
/** Compare two field elements. Requires magnitude-1 inputs. */
static int secp256k1_fe_equal_var(const secp256k1_fe_t *a, const secp256k1_fe_t *b);
/** Compare two field elements. Requires both inputs to be normalized */
static int secp256k1_fe_cmp_var(const secp256k1_fe_t *a, const secp256k1_fe_t *b);

110
src/field_10x26_impl.h
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@ -103,6 +103,37 @@ static void secp256k1_fe_normalize(secp256k1_fe_t *r) {
#endif
}
static void secp256k1_fe_normalize_weak(secp256k1_fe_t *r) {
uint32_t t0 = r->n[0], t1 = r->n[1], t2 = r->n[2], t3 = r->n[3], t4 = r->n[4],
t5 = r->n[5], t6 = r->n[6], t7 = r->n[7], t8 = r->n[8], t9 = r->n[9];
/* Reduce t9 at the start so there will be at most a single carry from the first pass */
uint32_t x = t9 >> 22; t9 &= 0x03FFFFFUL;
/* The first pass ensures the magnitude is 1, ... */
t0 += x * 0x3D1UL; t1 += (x << 6);
t1 += (t0 >> 26); t0 &= 0x3FFFFFFUL;
t2 += (t1 >> 26); t1 &= 0x3FFFFFFUL;
t3 += (t2 >> 26); t2 &= 0x3FFFFFFUL;
t4 += (t3 >> 26); t3 &= 0x3FFFFFFUL;
t5 += (t4 >> 26); t4 &= 0x3FFFFFFUL;
t6 += (t5 >> 26); t5 &= 0x3FFFFFFUL;
t7 += (t6 >> 26); t6 &= 0x3FFFFFFUL;
t8 += (t7 >> 26); t7 &= 0x3FFFFFFUL;
t9 += (t8 >> 26); t8 &= 0x3FFFFFFUL;
/* ... except for a possible carry at bit 22 of t9 (i.e. bit 256 of the field element) */
VERIFY_CHECK(t9 >> 23 == 0);
r->n[0] = t0; r->n[1] = t1; r->n[2] = t2; r->n[3] = t3; r->n[4] = t4;
r->n[5] = t5; r->n[6] = t6; r->n[7] = t7; r->n[8] = t8; r->n[9] = t9;
#ifdef VERIFY
r->magnitude = 1;
secp256k1_fe_verify(r);
#endif
}
static void secp256k1_fe_normalize_var(secp256k1_fe_t *r) {
uint32_t t0 = r->n[0], t1 = r->n[1], t2 = r->n[2], t3 = r->n[3], t4 = r->n[4],
t5 = r->n[5], t6 = r->n[6], t7 = r->n[7], t8 = r->n[8], t9 = r->n[9];
@ -159,6 +190,73 @@ static void secp256k1_fe_normalize_var(secp256k1_fe_t *r) {
#endif
}
static int secp256k1_fe_normalizes_to_zero(secp256k1_fe_t *r) {
uint32_t t0 = r->n[0], t1 = r->n[1], t2 = r->n[2], t3 = r->n[3], t4 = r->n[4],
t5 = r->n[5], t6 = r->n[6], t7 = r->n[7], t8 = r->n[8], t9 = r->n[9];
/* Reduce t9 at the start so there will be at most a single carry from the first pass */
uint32_t x = t9 >> 22; t9 &= 0x03FFFFFUL;
/* z0 tracks a possible raw value of 0, z1 tracks a possible raw value of P */
uint32_t z0, z1;
/* The first pass ensures the magnitude is 1, ... */
t0 += x * 0x3D1UL; t1 += (x << 6);
t1 += (t0 >> 26); t0 &= 0x3FFFFFFUL; z0 = t0; z1 = t0 ^ 0x3D0UL;
t2 += (t1 >> 26); t1 &= 0x3FFFFFFUL; z0 |= t1; z1 &= t1 ^ 0x40UL;
t3 += (t2 >> 26); t2 &= 0x3FFFFFFUL; z0 |= t2; z1 &= t2;
t4 += (t3 >> 26); t3 &= 0x3FFFFFFUL; z0 |= t3; z1 &= t3;
t5 += (t4 >> 26); t4 &= 0x3FFFFFFUL; z0 |= t4; z1 &= t4;
t6 += (t5 >> 26); t5 &= 0x3FFFFFFUL; z0 |= t5; z1 &= t5;
t7 += (t6 >> 26); t6 &= 0x3FFFFFFUL; z0 |= t6; z1 &= t6;
t8 += (t7 >> 26); t7 &= 0x3FFFFFFUL; z0 |= t7; z1 &= t7;
t9 += (t8 >> 26); t8 &= 0x3FFFFFFUL; z0 |= t8; z1 &= t8;
z0 |= t9; z1 &= t9 ^ 0x3C00000UL;
/* ... except for a possible carry at bit 22 of t9 (i.e. bit 256 of the field element) */
VERIFY_CHECK(t9 >> 23 == 0);
return (z0 == 0) | (z1 == 0x3FFFFFFUL);
}
static int secp256k1_fe_normalizes_to_zero_var(secp256k1_fe_t *r) {
uint32_t t0 = r->n[0], t9 = r->n[9];
/* Reduce t9 at the start so there will be at most a single carry from the first pass */
uint32_t x = t9 >> 22;
/* The first pass ensures the magnitude is 1, ... */
t0 += x * 0x3D1UL;
/* z0 tracks a possible raw value of 0, z1 tracks a possible raw value of P */
uint32_t z0 = t0 & 0x3FFFFFFUL, z1 = z0 ^ 0x3D0UL;
/* Fast return path should catch the majority of cases */
if ((z0 != 0UL) & (z1 != 0x3FFFFFFUL))
return 0;
uint32_t t1 = r->n[1], t2 = r->n[2], t3 = r->n[3], t4 = r->n[4],
t5 = r->n[5], t6 = r->n[6], t7 = r->n[7], t8 = r->n[8];
t9 &= 0x03FFFFFUL;
t1 += (x << 6);
t1 += (t0 >> 26); t0 = z0;
t2 += (t1 >> 26); t1 &= 0x3FFFFFFUL; z0 |= t1; z1 &= t1 ^ 0x40UL;
t3 += (t2 >> 26); t2 &= 0x3FFFFFFUL; z0 |= t2; z1 &= t2;
t4 += (t3 >> 26); t3 &= 0x3FFFFFFUL; z0 |= t3; z1 &= t3;
t5 += (t4 >> 26); t4 &= 0x3FFFFFFUL; z0 |= t4; z1 &= t4;
t6 += (t5 >> 26); t5 &= 0x3FFFFFFUL; z0 |= t5; z1 &= t5;
t7 += (t6 >> 26); t6 &= 0x3FFFFFFUL; z0 |= t6; z1 &= t6;
t8 += (t7 >> 26); t7 &= 0x3FFFFFFUL; z0 |= t7; z1 &= t7;
t9 += (t8 >> 26); t8 &= 0x3FFFFFFUL; z0 |= t8; z1 &= t8;
z0 |= t9; z1 &= t9 ^ 0x3C00000UL;
/* ... except for a possible carry at bit 22 of t9 (i.e. bit 256 of the field element) */
VERIFY_CHECK(t9 >> 23 == 0);
return (z0 == 0) | (z1 == 0x3FFFFFFUL);
}
SECP256K1_INLINE static void secp256k1_fe_set_int(secp256k1_fe_t *r, int a) {
r->n[0] = a;
r->n[1] = r->n[2] = r->n[3] = r->n[4] = r->n[5] = r->n[6] = r->n[7] = r->n[8] = r->n[9] = 0;
@ -196,18 +294,6 @@ SECP256K1_INLINE static void secp256k1_fe_clear(secp256k1_fe_t *a) {
}
}
SECP256K1_INLINE static int secp256k1_fe_equal(const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
#ifdef VERIFY
VERIFY_CHECK(a->normalized);
VERIFY_CHECK(b->normalized);
secp256k1_fe_verify(a);
secp256k1_fe_verify(b);
#endif
const uint32_t *t = a->n, *u = b->n;
return ((t[0]^u[0]) | (t[1]^u[1]) | (t[2]^u[2]) | (t[3]^u[3]) | (t[4]^u[4])
| (t[5]^u[5]) | (t[6]^u[6]) | (t[7]^u[7]) | (t[8]^u[8]) | (t[9]^u[9])) == 0;
}
static int secp256k1_fe_cmp_var(const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
#ifdef VERIFY
VERIFY_CHECK(a->normalized);

89
src/field_5x52_impl.h
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@ -100,6 +100,30 @@ static void secp256k1_fe_normalize(secp256k1_fe_t *r) {
#endif
}
static void secp256k1_fe_normalize_weak(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;
/* The first pass ensures the magnitude is 1, ... */
t0 += x * 0x1000003D1ULL;
t1 += (t0 >> 52); t0 &= 0xFFFFFFFFFFFFFULL;
t2 += (t1 >> 52); t1 &= 0xFFFFFFFFFFFFFULL;
t3 += (t2 >> 52); t2 &= 0xFFFFFFFFFFFFFULL;
t4 += (t3 >> 52); t3 &= 0xFFFFFFFFFFFFFULL;
/* ... except for a possible carry at bit 48 of t4 (i.e. bit 256 of the field element) */
VERIFY_CHECK(t4 >> 49 == 0);
r->n[0] = t0; r->n[1] = t1; r->n[2] = t2; r->n[3] = t3; r->n[4] = t4;
#ifdef VERIFY
r->magnitude = 1;
secp256k1_fe_verify(r);
#endif
}
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];
@ -144,6 +168,60 @@ static void secp256k1_fe_normalize_var(secp256k1_fe_t *r) {
#endif
}
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;
/* The first pass ensures the magnitude is 1, ... */
t0 += x * 0x1000003D1ULL;
t1 += (t0 >> 52); t0 &= 0xFFFFFFFFFFFFFULL; z0 = t0; z1 = t0 ^ 0x1000003D0ULL;
t2 += (t1 >> 52); t1 &= 0xFFFFFFFFFFFFFULL; z0 |= t1; z1 &= t1;
t3 += (t2 >> 52); t2 &= 0xFFFFFFFFFFFFFULL; z0 |= t2; z1 &= t2;
t4 += (t3 >> 52); t3 &= 0xFFFFFFFFFFFFFULL; z0 |= t3; z1 &= t3;
z0 |= t4; z1 &= t4 ^ 0xF000000000000ULL;
/* ... except for a possible carry at bit 48 of t4 (i.e. bit 256 of the field element) */
VERIFY_CHECK(t4 >> 49 == 0);
return (z0 == 0) | (z1 == 0xFFFFFFFFFFFFFULL);
}
static int secp256k1_fe_normalizes_to_zero_var(secp256k1_fe_t *r) {
uint64_t 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;
/* 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;
/* 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];
t4 &= 0x0FFFFFFFFFFFFULL;
t1 += (t0 >> 52); t0 = z0;
t2 += (t1 >> 52); t1 &= 0xFFFFFFFFFFFFFULL; z0 |= t1; z1 &= t1;
t3 += (t2 >> 52); t2 &= 0xFFFFFFFFFFFFFULL; z0 |= t2; z1 &= t2;
t4 += (t3 >> 52); t3 &= 0xFFFFFFFFFFFFFULL; z0 |= t3; z1 &= t3;
z0 |= t4; z1 &= t4 ^ 0xF000000000000ULL;
/* ... except for a possible carry at bit 48 of t4 (i.e. bit 256 of the field element) */
VERIFY_CHECK(t4 >> 49 == 0);
return (z0 == 0) | (z1 == 0xFFFFFFFFFFFFFULL);
}
SECP256K1_INLINE static void secp256k1_fe_set_int(secp256k1_fe_t *r, int a) {
r->n[0] = a;
r->n[1] = r->n[2] = r->n[3] = r->n[4] = 0;
@ -181,17 +259,6 @@ SECP256K1_INLINE static void secp256k1_fe_clear(secp256k1_fe_t *a) {
}
}
SECP256K1_INLINE static int secp256k1_fe_equal(const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
#ifdef VERIFY
VERIFY_CHECK(a->normalized);
VERIFY_CHECK(b->normalized);
secp256k1_fe_verify(a);
secp256k1_fe_verify(b);
#endif
const uint64_t *t = a->n, *u = b->n;
return ((t[0]^u[0]) | (t[1]^u[1]) | (t[2]^u[2]) | (t[3]^u[3]) | (t[4]^u[4])) == 0;
}
static int secp256k1_fe_cmp_var(const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
#ifdef VERIFY
VERIFY_CHECK(a->normalized);

7
src/field_impl.h
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@ -64,6 +64,13 @@ static int secp256k1_fe_set_hex(secp256k1_fe_t *r, const char *a, int alen) {
return secp256k1_fe_set_b32(r, tmp);
}
SECP256K1_INLINE static int secp256k1_fe_equal_var(const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
secp256k1_fe_t na;
secp256k1_fe_negate(&na, a, 1);
secp256k1_fe_add(&na, b);
return secp256k1_fe_normalizes_to_zero_var(&na);
}
static int secp256k1_fe_sqrt_var(secp256k1_fe_t *r, const secp256k1_fe_t *a) {
/** The binary representation of (p + 1)/4 has 3 blocks of 1s, with lengths in

3
src/group.h
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@ -60,7 +60,6 @@ static int secp256k1_ge_is_infinity(const secp256k1_ge_t *a);
static int secp256k1_ge_is_valid_var(const secp256k1_ge_t *a);
static void secp256k1_ge_neg(secp256k1_ge_t *r, const secp256k1_ge_t *a);
static void secp256k1_ge_neg_var(secp256k1_ge_t *r, const secp256k1_ge_t *a);
/** Get a hex representation of a point. *rlen will be overwritten with the real length. */
static void secp256k1_ge_get_hex(char *r, int *rlen, const secp256k1_ge_t *a);
@ -85,7 +84,7 @@ static void secp256k1_gej_set_ge(secp256k1_gej_t *r, const secp256k1_ge_t *a);
static int secp256k1_gej_eq_x_var(const secp256k1_fe_t *x, const secp256k1_gej_t *a);
/** Set r equal to the inverse of a (i.e., mirrored around the X axis) */
static void secp256k1_gej_neg_var(secp256k1_gej_t *r, const secp256k1_gej_t *a);
static void secp256k1_gej_neg(secp256k1_gej_t *r, const secp256k1_gej_t *a);
/** Check whether a group element is the point at infinity. */
static int secp256k1_gej_is_infinity(const secp256k1_gej_t *a);

64
src/group_impl.h
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@ -29,13 +29,7 @@ static int secp256k1_ge_is_infinity(const secp256k1_ge_t *a) {
static void secp256k1_ge_neg(secp256k1_ge_t *r, const secp256k1_ge_t *a) {
*r = *a;
secp256k1_fe_normalize(&r->y);
secp256k1_fe_negate(&r->y, &r->y, 1);
}
static void secp256k1_ge_neg_var(secp256k1_ge_t *r, const secp256k1_ge_t *a) {
*r = *a;
secp256k1_fe_normalize_var(&r->y);
secp256k1_fe_normalize_weak(&r->y);
secp256k1_fe_negate(&r->y, &r->y, 1);
}
@ -166,18 +160,16 @@ static void secp256k1_gej_set_ge(secp256k1_gej_t *r, const secp256k1_ge_t *a) {
static int secp256k1_gej_eq_x_var(const secp256k1_fe_t *x, const secp256k1_gej_t *a) {
VERIFY_CHECK(!a->infinity);
secp256k1_fe_t r; secp256k1_fe_sqr(&r, &a->z); secp256k1_fe_mul(&r, &r, x);
secp256k1_fe_t r2 = a->x;
secp256k1_fe_normalize_var(&r);
secp256k1_fe_normalize_var(&r2);
return secp256k1_fe_equal(&r, &r2);
secp256k1_fe_t r2 = a->x; secp256k1_fe_normalize_weak(&r2);
return secp256k1_fe_equal_var(&r, &r2);
}
static void secp256k1_gej_neg_var(secp256k1_gej_t *r, const secp256k1_gej_t *a) {
static void secp256k1_gej_neg(secp256k1_gej_t *r, const secp256k1_gej_t *a) {
r->infinity = a->infinity;
r->x = a->x;
r->y = a->y;
r->z = a->z;
secp256k1_fe_normalize_var(&r->y);
secp256k1_fe_normalize_weak(&r->y);
secp256k1_fe_negate(&r->y, &r->y, 1);
}
@ -199,9 +191,8 @@ static int secp256k1_gej_is_valid_var(const secp256k1_gej_t *a) {
secp256k1_fe_t z6; secp256k1_fe_sqr(&z6, &z2); secp256k1_fe_mul(&z6, &z6, &z2);
secp256k1_fe_mul_int(&z6, 7);
secp256k1_fe_add(&x3, &z6);
secp256k1_fe_normalize_var(&y2);
secp256k1_fe_normalize_var(&x3);
return secp256k1_fe_equal(&y2, &x3);
secp256k1_fe_normalize_weak(&x3);
return secp256k1_fe_equal_var(&y2, &x3);
}
static int secp256k1_ge_is_valid_var(const secp256k1_ge_t *a) {
@ -212,9 +203,8 @@ static int secp256k1_ge_is_valid_var(const secp256k1_ge_t *a) {
secp256k1_fe_t x3; secp256k1_fe_sqr(&x3, &a->x); secp256k1_fe_mul(&x3, &x3, &a->x);
secp256k1_fe_t c; secp256k1_fe_set_int(&c, 7);
secp256k1_fe_add(&x3, &c);
secp256k1_fe_normalize_var(&y2);
secp256k1_fe_normalize_var(&x3);
return secp256k1_fe_equal(&y2, &x3);
secp256k1_fe_normalize_weak(&x3);
return secp256k1_fe_equal_var(&y2, &x3);
}
static void secp256k1_gej_double_var(secp256k1_gej_t *r, const secp256k1_gej_t *a) {
@ -265,20 +255,16 @@ static void secp256k1_gej_add_var(secp256k1_gej_t *r, const secp256k1_gej_t *a,
secp256k1_fe_t u2; secp256k1_fe_mul(&u2, &b->x, &z12);
secp256k1_fe_t s1; secp256k1_fe_mul(&s1, &a->y, &z22); secp256k1_fe_mul(&s1, &s1, &b->z);
secp256k1_fe_t s2; secp256k1_fe_mul(&s2, &b->y, &z12); secp256k1_fe_mul(&s2, &s2, &a->z);
secp256k1_fe_normalize_var(&u1);
secp256k1_fe_normalize_var(&u2);
if (secp256k1_fe_equal(&u1, &u2)) {
secp256k1_fe_normalize_var(&s1);
secp256k1_fe_normalize_var(&s2);
if (secp256k1_fe_equal(&s1, &s2)) {
secp256k1_fe_t h; secp256k1_fe_negate(&h, &u1, 1); secp256k1_fe_add(&h, &u2);
secp256k1_fe_t i; secp256k1_fe_negate(&i, &s1, 1); secp256k1_fe_add(&i, &s2);
if (secp256k1_fe_normalizes_to_zero_var(&h)) {
if (secp256k1_fe_normalizes_to_zero_var(&i)) {
secp256k1_gej_double_var(r, a);
} else {
r->infinity = 1;
}
return;
}
secp256k1_fe_t h; secp256k1_fe_negate(&h, &u1, 1); secp256k1_fe_add(&h, &u2);
secp256k1_fe_t i; secp256k1_fe_negate(&i, &s1, 1); secp256k1_fe_add(&i, &s2);
secp256k1_fe_t i2; secp256k1_fe_sqr(&i2, &i);
secp256k1_fe_t h2; secp256k1_fe_sqr(&h2, &h);
secp256k1_fe_t h3; secp256k1_fe_mul(&h3, &h, &h2);
@ -304,23 +290,20 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej_t *r, const secp256k1_gej_t *
}
r->infinity = 0;
secp256k1_fe_t z12; secp256k1_fe_sqr(&z12, &a->z);
secp256k1_fe_t u1 = a->x;
secp256k1_fe_t u1 = a->x; secp256k1_fe_normalize_weak(&u1);
secp256k1_fe_t u2; secp256k1_fe_mul(&u2, &b->x, &z12);
secp256k1_fe_t s1 = a->y; secp256k1_fe_normalize_var(&s1);
secp256k1_fe_t s1 = a->y; secp256k1_fe_normalize_weak(&s1);
secp256k1_fe_t s2; secp256k1_fe_mul(&s2, &b->y, &z12); secp256k1_fe_mul(&s2, &s2, &a->z);
secp256k1_fe_normalize_var(&u1);
secp256k1_fe_normalize_var(&u2);
if (secp256k1_fe_equal(&u1, &u2)) {
secp256k1_fe_normalize_var(&s2);
if (secp256k1_fe_equal(&s1, &s2)) {
secp256k1_fe_t h; secp256k1_fe_negate(&h, &u1, 1); secp256k1_fe_add(&h, &u2);
secp256k1_fe_t i; secp256k1_fe_negate(&i, &s1, 1); secp256k1_fe_add(&i, &s2);
if (secp256k1_fe_normalizes_to_zero_var(&h)) {
if (secp256k1_fe_normalizes_to_zero_var(&i)) {
secp256k1_gej_double_var(r, a);
} else {
r->infinity = 1;
}
return;
}
secp256k1_fe_t h; secp256k1_fe_negate(&h, &u1, 1); secp256k1_fe_add(&h, &u2);
secp256k1_fe_t i; secp256k1_fe_negate(&i, &s1, 1); secp256k1_fe_add(&i, &s2);
secp256k1_fe_t i2; secp256k1_fe_sqr(&i2, &i);
secp256k1_fe_t h2; secp256k1_fe_sqr(&h2, &h);
secp256k1_fe_t h3; secp256k1_fe_mul(&h3, &h, &h2);
@ -359,9 +342,9 @@ static void secp256k1_gej_add_ge(secp256k1_gej_t *r, const secp256k1_gej_t *a, c
*/
secp256k1_fe_t zz; secp256k1_fe_sqr(&zz, &a->z); /* z = Z1^2 */
secp256k1_fe_t u1 = a->x; secp256k1_fe_normalize(&u1); /* u1 = U1 = X1*Z2^2 (1) */
secp256k1_fe_t u1 = a->x; secp256k1_fe_normalize_weak(&u1); /* u1 = U1 = X1*Z2^2 (1) */
secp256k1_fe_t u2; secp256k1_fe_mul(&u2, &b->x, &zz); /* u2 = U2 = X2*Z1^2 (1) */
secp256k1_fe_t s1 = a->y; secp256k1_fe_normalize(&s1); /* s1 = S1 = Y1*Z2^3 (1) */
secp256k1_fe_t s1 = a->y; secp256k1_fe_normalize_weak(&s1); /* s1 = S1 = Y1*Z2^3 (1) */
secp256k1_fe_t s2; secp256k1_fe_mul(&s2, &b->y, &zz); /* s2 = Y2*Z2^2 (1) */
secp256k1_fe_mul(&s2, &s2, &a->z); /* s2 = S2 = Y2*Z1^3 (1) */
secp256k1_fe_t z = a->z; /* z = Z = Z1*Z2 (8) */
@ -375,8 +358,7 @@ static void secp256k1_gej_add_ge(secp256k1_gej_t *r, const secp256k1_gej_t *a, c
secp256k1_fe_add(&rr, &t); /* rr = R = T^2-U1*U2 (3) */
secp256k1_fe_sqr(&t, &rr); /* t = R^2 (1) */
secp256k1_fe_mul(&r->z, &m, &z); /* r->z = M*Z (1) */
secp256k1_fe_normalize(&r->z);
int infinity = secp256k1_fe_is_zero(&r->z) * (1 - a->infinity);
int infinity = secp256k1_fe_normalizes_to_zero(&r->z) * (1 - a->infinity);
secp256k1_fe_mul_int(&r->z, 2 * (1 - a->infinity)); /* r->z = Z3 = 2*M*Z (2) */
r->x = t; /* r->x = R^2 (1) */
secp256k1_fe_negate(&q, &q, 1); /* q = -Q (2) */
@ -388,7 +370,7 @@ static void secp256k1_gej_add_ge(secp256k1_gej_t *r, const secp256k1_gej_t *a, c
secp256k1_fe_mul(&t, &t, &rr); /* t = R*(2*R^2-3*Q) (1) */
secp256k1_fe_add(&t, &n); /* t = R*(2*R^2-3*Q)+M^4 (2) */
secp256k1_fe_negate(&r->y, &t, 2); /* r->y = R*(3*Q-2*R^2)-M^4 (3) */
secp256k1_fe_normalize(&r->y);
secp256k1_fe_normalize_weak(&r->y);
secp256k1_fe_mul_int(&r->x, 4 * (1 - a->infinity)); /* r->x = X3 = 4*(R^2-Q) */
secp256k1_fe_mul_int(&r->y, 4 * (1 - a->infinity)); /* r->y = Y3 = 4*R*(3*Q-2*R^2)-4*M^4 (4) */

10
src/tests.c
View File

@ -494,9 +494,9 @@ void random_fe_non_square(secp256k1_fe_t *ns) {
}
int check_fe_equal(const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
secp256k1_fe_t an = *a; secp256k1_fe_normalize(&an);
secp256k1_fe_t an = *a; secp256k1_fe_normalize_weak(&an);
secp256k1_fe_t bn = *b; secp256k1_fe_normalize_var(&bn);
return secp256k1_fe_equal(&an, &bn);
return secp256k1_fe_equal_var(&an, &bn);
}
int check_fe_inverse(const secp256k1_fe_t *a, const secp256k1_fe_t *ai) {
@ -523,16 +523,16 @@ void run_field_misc(void) {
random_fe_non_zero(&y);
/* Test the fe equality and comparison operations. */
CHECK(secp256k1_fe_cmp_var(&x, &x) == 0);
CHECK(secp256k1_fe_equal(&x, &x));
CHECK(secp256k1_fe_equal_var(&x, &x));
z = x;
secp256k1_fe_add(&z,&y);
secp256k1_fe_normalize(&z);
/* Test the conditional move. */
secp256k1_fe_cmov(&z, &x, 0);
CHECK(secp256k1_fe_equal(&x, &z) == 0);
CHECK(secp256k1_fe_equal_var(&x, &z) == 0);
CHECK(secp256k1_fe_cmp_var(&x, &z) != 0);
secp256k1_fe_cmov(&y, &x, 1);
CHECK(secp256k1_fe_equal(&x, &y));
CHECK(secp256k1_fe_equal_var(&x, &y));
/* Test that mul_int, mul, and add agree. */
secp256k1_fe_add(&y, &x);
secp256k1_fe_add(&y, &x);