Merge commit from fork

Author: Markus-MS

lib/elliptic/eddsa/index.js

@@ -52,6 +52,9 @@ EDDSA.prototype.sign = function sign(message, secret) {
 EDDSA.prototype.verify = function verify(message, sig, pub) {
   message = parseBytes(message);
   sig = this.makeSignature(sig);
+  if (sig.S().gte(sig.eddsa.curve.n) || sig.S().isNeg()) {
+    return false;
+  }
   var key = this.keyFromPublic(pub);
   var h = this.hashInt(sig.Rencoded(), key.pubBytes(), message);
   var SG = this.g.mul(sig.S());