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Abstract out verify logic for fe_is_square_var

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This commit is contained in:
Pieter Wuille 2023-05-11 03:16:00 -04:00
parent 4371f98346
commit 4e176ad5b9
4 changed files with 18 additions and 11 deletions
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6
src/field.h
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@ -100,6 +100,7 @@ static const secp256k1_fe secp256k1_const_beta = SECP256K1_FE_CONST(
# define secp256k1_fe_get_bounds secp256k1_fe_impl_get_bounds # define secp256k1_fe_get_bounds secp256k1_fe_impl_get_bounds
# define secp256k1_fe_half secp256k1_fe_impl_half # define secp256k1_fe_half secp256k1_fe_impl_half
# define secp256k1_fe_add_int secp256k1_fe_impl_add_int # define secp256k1_fe_add_int secp256k1_fe_impl_add_int
# define secp256k1_fe_is_square_var secp256k1_fe_impl_is_square_var
#endif /* !defined(VERIFY) */ #endif /* !defined(VERIFY) */
/** Normalize a field element. /** Normalize a field element.
@ -321,7 +322,10 @@ static void secp256k1_fe_half(secp256k1_fe *r);
* internal overflows. */ * internal overflows. */
static void secp256k1_fe_get_bounds(secp256k1_fe *r, int m); static void secp256k1_fe_get_bounds(secp256k1_fe *r, int m);
/** Determine whether a is a square (modulo p). */ /** Determine whether a is a square (modulo p).
*
* On input, a must be a valid field element.
*/
static int secp256k1_fe_is_square_var(const secp256k1_fe *a); static int secp256k1_fe_is_square_var(const secp256k1_fe *a);
/** Check invariants on a field element (no-op unless VERIFY is enabled). */ /** Check invariants on a field element (no-op unless VERIFY is enabled). */

6
src/field_10x26_impl.h
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@ -1215,7 +1215,7 @@ static void secp256k1_fe_impl_inv_var(secp256k1_fe *r, const secp256k1_fe *x) {
secp256k1_fe_from_signed30(r, &s); secp256k1_fe_from_signed30(r, &s);
} }
static int secp256k1_fe_is_square_var(const secp256k1_fe *x) { static int secp256k1_fe_impl_is_square_var(const secp256k1_fe *x) {
secp256k1_fe tmp; secp256k1_fe tmp;
secp256k1_modinv32_signed30 s; secp256k1_modinv32_signed30 s;
int jac, ret; int jac, ret;
@ -1233,10 +1233,6 @@ static int secp256k1_fe_is_square_var(const secp256k1_fe *x) {
secp256k1_fe dummy; secp256k1_fe dummy;
ret = secp256k1_fe_sqrt(&dummy, &tmp); ret = secp256k1_fe_sqrt(&dummy, &tmp);
} else { } else {
#ifdef VERIFY
secp256k1_fe dummy;
VERIFY_CHECK(jac == 2*secp256k1_fe_sqrt(&dummy, &tmp) - 1);
#endif
ret = jac >= 0; ret = jac >= 0;
} }
return ret; return ret;

6
src/field_5x52_impl.h
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@ -504,7 +504,7 @@ static void secp256k1_fe_impl_inv_var(secp256k1_fe *r, const secp256k1_fe *x) {
secp256k1_fe_from_signed62(r, &s); secp256k1_fe_from_signed62(r, &s);
} }
static int secp256k1_fe_is_square_var(const secp256k1_fe *x) { static int secp256k1_fe_impl_is_square_var(const secp256k1_fe *x) {
secp256k1_fe tmp; secp256k1_fe tmp;
secp256k1_modinv64_signed62 s; secp256k1_modinv64_signed62 s;
int jac, ret; int jac, ret;
@ -522,10 +522,6 @@ static int secp256k1_fe_is_square_var(const secp256k1_fe *x) {
secp256k1_fe dummy; secp256k1_fe dummy;
ret = secp256k1_fe_sqrt(&dummy, &tmp); ret = secp256k1_fe_sqrt(&dummy, &tmp);
} else { } else {
#ifdef VERIFY
secp256k1_fe dummy;
VERIFY_CHECK(jac == 2*secp256k1_fe_sqrt(&dummy, &tmp) - 1);
#endif
ret = jac >= 0; ret = jac >= 0;
} }
return ret; return ret;

11
src/field_impl.h
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@ -384,6 +384,17 @@ SECP256K1_INLINE static void secp256k1_fe_inv_var(secp256k1_fe *r, const secp256
secp256k1_fe_verify(r); secp256k1_fe_verify(r);
} }
static int secp256k1_fe_impl_is_square_var(const secp256k1_fe *x);
SECP256K1_INLINE static int secp256k1_fe_is_square_var(const secp256k1_fe *x) {
int ret;
secp256k1_fe tmp = *x, sqrt;
secp256k1_fe_verify(x);
ret = secp256k1_fe_impl_is_square_var(x);
secp256k1_fe_normalize_weak(&tmp);
VERIFY_CHECK(ret == secp256k1_fe_sqrt(&sqrt, &tmp));
return ret;
}
static void secp256k1_fe_impl_get_bounds(secp256k1_fe* r, int m); static void secp256k1_fe_impl_get_bounds(secp256k1_fe* r, int m);
SECP256K1_INLINE static void secp256k1_fe_get_bounds(secp256k1_fe* r, int m) { SECP256K1_INLINE static void secp256k1_fe_get_bounds(secp256k1_fe* r, int m) {
VERIFY_CHECK(m >= 0); VERIFY_CHECK(m >= 0);