change key_size to 128bits on message encryption

lib/walletutils.js

@@ -84,9 +84,9 @@ WalletUtils.fromSecret = function(secret) {
 WalletUtils.encryptMessage = function(message, privKey) {
   var hash = sjcl.hash.sha256.hash(privKey);
   var key = sjcl.codec.utf8String.toBits(hash);
-  key = sjcl.bitArray.clamp(key, 256);
+  key = sjcl.bitArray.clamp(key, 128);
   return sjcl.encrypt(key, message, {
-    ks: 256,
+    ks: 128,
     iter: 1
   });
 };
@@ -94,7 +94,7 @@ WalletUtils.encryptMessage = function(message, privKey) {
 WalletUtils.decryptMessage = function(cyphertextJson, privKey) {
   var hash = sjcl.hash.sha256.hash(privKey);
   var key = sjcl.codec.utf8String.toBits(hash);
-  key = sjcl.bitArray.clamp(key, 256);
+  key = sjcl.bitArray.clamp(key, 128);
   return sjcl.decrypt(key, cyphertextJson);
 };