From: Loup Vaillant <loup@loup-vaillant.fr>
Date: Thu, 20 Feb 2020 23:00:44 +0000 (+0100)
Subject: Elligator script: removed erroneous .abs()
X-Git-Url: https://git.codecow.com/?a=commitdiff_plain;h=128b567c5a694521342e27ecd19c49a4fbf02ba0;p=Monocypher.git

Elligator script: removed erroneous .abs()

Changing the sign of the v coordinate had an effect on the final value
of the final hash, but wasn't detected because my initial tests only
compare to the u coordinate, which appears to be correct.

This doesn't affect the success or failure of the Elligator mapping,
which only look at the u coordinate.  Yet another example of incorrect
crypto that looks like it works...
---

diff --git a/tests/gen/elligator.py b/tests/gen/elligator.py
index dc3073a..f5ef516 100755
--- a/tests/gen/elligator.py
+++ b/tests/gen/elligator.py
@@ -175,7 +175,7 @@ def from_edwards(point):
     x = point[0]
     y = point[1]
     u = (fe(1) + y) / (fe(1) - y)
-    v = (sqrt(fe(-486664)) * u / x).abs()
+    v = (sqrt(fe(-486664)) * u / x)
     return (u, v)
 
 # entire key generation chain