From f3edfe59c7aa574e9e96f951d70bc0fdd9872cdd Mon Sep 17 00:00:00 2001
From: Kirill Fomichev <fanatid@ya.ru>
Date: Wed, 14 Sep 2016 13:41:34 +0300
Subject: [PATCH] ec: speedup ec.recoverPubKey

PR-URL: https://github.com/indutny/elliptic/pull/104
Reviewed-By: Fedor Indutny <fedor@indutny.com>
---
 lib/elliptic/ec/index.js | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/lib/elliptic/ec/index.js b/lib/elliptic/ec/index.js
index b7fa666..d71d5df 100644
--- a/lib/elliptic/ec/index.js
+++ b/lib/elliptic/ec/index.js
@@ -208,12 +208,13 @@ EC.prototype.recoverPubKey = function(msg, signature, j, enc) {
   else
     r = this.curve.pointFromX(r, isYOdd);
 
-  var eNeg = n.sub(e);
+  var rInv = signature.r.invm(n);
+  var s1 = n.sub(e).mul(rInv).umod(n);
+  var s2 = s.mul(rInv).umod(n);
 
   // 1.6.1 Compute Q = r^-1 (sR -  eG)
   //               Q = r^-1 (sR + -eG)
-  var rInv = signature.r.invm(n);
-  return this.g.mulAdd(eNeg, r, s).mul(rInv);
+  return this.g.mulAdd(s1, r, s2);
 };
 
 EC.prototype.getKeyRecoveryParam = function(e, signature, Q, enc) {