From: Loup Vaillant <loup@loup-vaillant.fr>
Date: Mon, 9 Mar 2020 19:40:24 +0000 (+0100)
Subject: Typo, comment fe_isnegative()
X-Git-Url: https://git.codecow.com/?a=commitdiff_plain;h=dae1fdba96f806dd19ac319653a7fdff71796492;p=Monocypher.git

Typo, comment fe_isnegative()
---

diff --git a/src/monocypher.c b/src/monocypher.c
index 7af9030..266eadd 100644
--- a/src/monocypher.c
+++ b/src/monocypher.c
@@ -1316,6 +1316,11 @@ static int fe_isodd(const fe f)
     return isodd;
 }
 
+// Returns 0 if f <= (p-1)/2, 1 otherwise.
+// "Positive" means between 0 and (p-1)/2
+// "Negative" means between (p+1)/2 and p-1
+// Since p is odd (2^255 - 19), the sign is easily tested by leveraging
+// overflow: for any f in [0..p[, (2*f)%p is odd iff 2*f > p
 static int fe_isnegative(const fe f)
 {
     fe tmp;
@@ -1335,7 +1340,7 @@ static int fe_isnonzero(const fe f)
     return -isnonzero;
 }
 
-// Returns 1 if equal, 0 of not equal
+// Returns 1 if equal, 0 if not equal
 static int fe_isequal(const fe f, const fe g)
 {
     fe diff;