From 971bed6ab4b27014eb23085e8176917e1a096fd5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
Date: Sat, 13 Mar 2021 17:26:37 +0100
Subject: [PATCH] Use ecc_mod_mul_canonical for point comparison.

* eddsa-verify.c (equal_h): Use ecc_mod_mul_canonical.

(cherry picked from commit 5b7608fde3a6d2ab82bffb35db1e4e330927c906)
---
 ChangeLog      | 4 ++++
 eddsa-verify.c | 9 ++-------
 2 files changed, 6 insertions(+), 7 deletions(-)

#diff --git a/ChangeLog b/ChangeLog
#index 5cc5c188..2a9217a6 100644
#--- a/ChangeLog
#+++ b/ChangeLog
#@@ -1,3 +1,7 @@
#+2021-03-13  Niels Möller  <nisse@lysator.liu.se>
#+
#+	* eddsa-verify.c (equal_h): Use ecc_mod_mul_canonical.
#+
# 2021-03-11  Niels Möller  <nisse@lysator.liu.se>
# 
# 	* ecc-mod-arith.c (ecc_mod_mul_canonical, ecc_mod_sqr_canonical):
--- a/eddsa-verify.c
+++ b/eddsa-verify.c
@@ -53,13 +53,8 @@ equal_h (const struct ecc_modulo *p,
 #define t0 scratch
 #define t1 (scratch + p->size)
 
-  ecc_mod_mul (p, t0, x1, z2);
-  if (mpn_cmp (t0, p->m, p->size) >= 0)
-    mpn_sub_n (t0, t0, p->m, p->size);
-
-  ecc_mod_mul (p, t1, x2, z1);
-  if (mpn_cmp (t1, p->m, p->size) >= 0)
-    mpn_sub_n (t1, t1, p->m, p->size);
+  ecc_mod_mul_canonical (p, t0, x1, z2, t0);
+  ecc_mod_mul_canonical (p, t1, x2, z1, t1);
 
   return mpn_cmp (t0, t1, p->size) == 0;
 
