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Clarify comments about use of rzr on ge functions and abs function.

This commit is contained in:
Gregory Maxwell 2020-01-09 13:07:36 +00:00
parent 2241ae6d14
commit d567b779fe
2 changed files with 4 additions and 3 deletions
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1
src/ecmult_const_impl.h
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@ -15,6 +15,7 @@
/* This is like `ECMULT_TABLE_GET_GE` but is constant time */
#define ECMULT_CONST_TABLE_GET_GE(r,pre,n,w) do { \
int m; \
/* Extract the sign-bit for a constant time absolute-value. */ \
int mask = (n) >> (sizeof(n) * CHAR_BIT - 1); \
int abs_n = ((n) + mask) ^ mask; \
int idx_n = abs_n >> 1; \

6
src/group.h
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@ -98,10 +98,10 @@ static int secp256k1_gej_has_quad_y_var(const secp256k1_gej *a);
/** Set r equal to the double of a, a cannot be infinity. Constant time. */
static void secp256k1_gej_double_nonzero(secp256k1_gej *r, const secp256k1_gej *a);
/** Set r equal to the double of a. If rzr is not-NULL, r->z = a->z * *rzr (where infinity means an implicit z = 0). */
/** Set r equal to the double of a. If rzr is not-NULL this sets *rzr such that r->z == a->z * *rzr (where infinity means an implicit z = 0). */
static void secp256k1_gej_double_var(secp256k1_gej *r, const secp256k1_gej *a, secp256k1_fe *rzr);
/** Set r equal to the sum of a and b. If rzr is non-NULL, r->z = a->z * *rzr (a cannot be infinity in that case). */
/** Set r equal to the sum of a and b. If rzr is non-NULL this sets *rzr such that r->z == a->z * *rzr (a cannot be infinity in that case). */
static void secp256k1_gej_add_var(secp256k1_gej *r, const secp256k1_gej *a, const secp256k1_gej *b, secp256k1_fe *rzr);
/** Set r equal to the sum of a and b (with b given in affine coordinates, and not infinity). */
@ -109,7 +109,7 @@ static void secp256k1_gej_add_ge(secp256k1_gej *r, const secp256k1_gej *a, const
/** Set r equal to the sum of a and b (with b given in affine coordinates). This is more efficient
than secp256k1_gej_add_var. It is identical to secp256k1_gej_add_ge but without constant-time
guarantee, and b is allowed to be infinity. If rzr is non-NULL, r->z = a->z * *rzr (a cannot be infinity in that case). */
guarantee, and b is allowed to be infinity. If rzr is non-NULL this sets *rzr such that r->z == a->z * *rzr (a cannot be infinity in that case). */
static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, const secp256k1_ge *b, secp256k1_fe *rzr);
/** Set r equal to the sum of a and b (with the inverse of b's Z coordinate passed as bzinv). */