Fixed browser exception caused by lib/Curve.js

lib/Curve.js

@@ -4,14 +4,20 @@ var bignum = imports.bignum || require('bignum');
 var Point = imports.Point || require('./Point');
 
 var n = bignum.fromBuffer(new Buffer("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141", 'hex'), {size: 32});
-var G = new Point(bignum.fromBuffer(new Buffer("79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798", 'hex'), {size: 32}),
-                  bignum.fromBuffer(new Buffer("483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8", 'hex'), {size: 32}));
 
-/* secp256k1 curve */
+
 var Curve = function() {
 };
 
+/* secp256k1 curve */
+var G;
 Curve.getG = function() {
+  // don't use Point in top scope, causes exception in browser
+  // when Point is not loaded yet
+
+  // use cached version if available
+  G = G || new Point(bignum.fromBuffer(new Buffer("79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798", 'hex'), {size: 32}),
+                  bignum.fromBuffer(new Buffer("483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8", 'hex'), {size: 32}));
   return G;
 };