BN.js fixed nmask for us, so we use that now instead of our mask hack.

lib/contract.js

@@ -44,21 +44,11 @@ function zpad(buffer, length) {
     return buffer;
 }
 
-// There seems to be a but in maskn, so we are doing this for now.
-var bitmasks = [];
-(function() {
-    var mask = '';
-    for (var i = 0; i < 33; i++) {
-        bitmasks.push(new utils.BN(mask, 16));
-        mask += 'ff';
-    }
-})();
-
 function coderNumber(size, signed) {
     return {
         encode: function(value) {
             value = numberOrBN(value)
-            value = value.toTwos(size * 8).and(bitmasks[size]);
+            value = value.toTwos(size * 8).maskn(size * 8);
             if (signed) {
                 value = value.fromTwos(size * 8).toTwos(256);
             }
@@ -70,7 +60,7 @@ function coderNumber(size, signed) {
             if (signed) {
                 value = value.fromTwos(size * 8);
             } else {
-                value = value.and(bitmasks[size]);
+                value = value.maskn(size * 8);
             }
             return {
                 consumed: 32,

package.json

@@ -9,7 +9,7 @@
   },
   "dependencies": {
     "aes-js": "2.0.0",
-    "elliptic": "6.3.1",
+    "elliptic": "6.3.2",
     "inherits": "2.0.1",
     "pbkdf2": "3.0.4",
     "rlp": "2.0.0",