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Split fe_set_b32 into reducing and normalizing variants

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Pieter Wuille
2023-02-05 17:19:00 -05:00
parent 006ddc1f42
commit 5b32602295
16 changed files with 69 additions and 40 deletions
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21
src/field.h
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@@ -85,7 +85,8 @@ static const secp256k1_fe secp256k1_const_beta = SECP256K1_FE_CONST(
# define secp256k1_fe_is_zero secp256k1_fe_impl_is_zero
# define secp256k1_fe_is_odd secp256k1_fe_impl_is_odd
# define secp256k1_fe_cmp_var secp256k1_fe_impl_cmp_var
# define secp256k1_fe_set_b32 secp256k1_fe_impl_set_b32
# define secp256k1_fe_set_b32_mod secp256k1_fe_impl_set_b32_mod
# define secp256k1_fe_set_b32_limit secp256k1_fe_impl_set_b32_limit
# define secp256k1_fe_get_b32 secp256k1_fe_impl_get_b32
# define secp256k1_fe_negate secp256k1_fe_impl_negate
# define secp256k1_fe_mul_int secp256k1_fe_impl_mul_int
@@ -189,16 +190,20 @@ static int secp256k1_fe_equal_var(const secp256k1_fe *a, const secp256k1_fe *b);
*/
static int secp256k1_fe_cmp_var(const secp256k1_fe *a, const secp256k1_fe *b);
/** Set a field element equal to a provided 32-byte big endian value.
/** Set a field element equal to a provided 32-byte big endian value, reducing it.
*
* On input, r does not need to be initalized. a must be a pointer to an initialized 32-byte array.
* On output, r = a (mod p). It will have magnitude 1, and if (a < p), it will be normalized.
* If not, it will only be weakly normalized. Returns whether (a < p).
*
* Note that this function is unusual in that the normalization of the output depends on the
* run-time value of a.
* On output, r = a (mod p). It will have magnitude 1, and not be normalized.
*/
static int secp256k1_fe_set_b32(secp256k1_fe *r, const unsigned char *a);
static void secp256k1_fe_set_b32_mod(secp256k1_fe *r, const unsigned char *a);
/** Set a field element equal to a provided 32-byte big endian value, checking for overflow.
*
* On input, r does not need to be initalized. a must be a pointer to an initialized 32-byte array.
* On output, r = a if (a < p), it will be normalized with magnitude 1, and 1 is returned.
* If a >= p, 0 is returned, and r will be made invalid (and must not be used without overwriting).
*/
static int secp256k1_fe_set_b32_limit(secp256k1_fe *r, const unsigned char *a);
/** Convert a field element to 32-byte big endian byte array.
* On input, a must be a valid normalized field element, and r a pointer to a 32-byte array.