From d25d6ce7fbf940f2e20e668a2a30d066f66e39e2 Mon Sep 17 00:00:00 2001
From: Frank Denis <github@pureftpd.org>
Date: Sat, 21 Jul 2018 00:42:31 +0200
Subject: [PATCH] Invert (1-y) just before the multiplication by (1+y) for
 readability

---
 src/libsodium/crypto_sign/ed25519/ref10/keypair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libsodium/crypto_sign/ed25519/ref10/keypair.c b/src/libsodium/crypto_sign/ed25519/ref10/keypair.c
index 8bf3cec8..4b9bf0dc 100644
--- a/src/libsodium/crypto_sign/ed25519/ref10/keypair.c
+++ b/src/libsodium/crypto_sign/ed25519/ref10/keypair.c
@@ -61,9 +61,9 @@ crypto_sign_ed25519_pk_to_curve25519(unsigned char *curve25519_pk,
     }
     fe25519_1(one_minus_y);
     fe25519_sub(one_minus_y, one_minus_y, A.Y);
-    fe25519_invert(one_minus_y, one_minus_y);
     fe25519_1(x);
     fe25519_add(x, x, A.Y);
+    fe25519_invert(one_minus_y, one_minus_y);
     fe25519_mul(x, x, one_minus_y);
     fe25519_tobytes(curve25519_pk, x);