diff --git a/bitcore.js b/bitcore.js
index 43de754..282a9c8 100644
--- a/bitcore.js
+++ b/bitcore.js
@@ -43,7 +43,7 @@ Object.defineProperty(module.exports, 'BIP32', {get: function() {
   return require('./lib/HierarchicalKey');
 }});
 requireWhenAccessed('BIP39', './lib/BIP39');
-requireWhenAccessed('BIP39WordlistEn', './BIP39WordlistEn');
+requireWhenAccessed('BIP39WordlistEn', './lib/BIP39WordlistEn');
 requireWhenAccessed('Point', './lib/Point');
 requireWhenAccessed('Opcode', './lib/Opcode');
 requireWhenAccessed('Script', './lib/Script');
diff --git a/browser/build.js b/browser/build.js
index e938663..364a986 100644
--- a/browser/build.js
+++ b/browser/build.js
@@ -27,6 +27,9 @@ var modules = [
   'lib/Armory',
   'lib/Base58',
   'lib/HierarchicalKey',
+  'lib/BIP39',
+  'lib/BIP39WordlistEn',
+  'lib/cryptox',
   'lib/Block',
   'lib/Bloom',
   'lib/Connection',
diff --git a/lib/browser/cryptox.js b/lib/browser/cryptox.js
new file mode 100644
index 0000000..71647ea
--- /dev/null
+++ b/lib/browser/cryptox.js
@@ -0,0 +1,41 @@
+// Crypto extensions
+//
+// PBKDF2 with SHA512 - browser version
+
+var jssha = require('jssha')
+
+var pbkdf2_sha512 = function (password, salt, keylen, options) {
+    password = new Buffer(password);
+    salt = new Buffer(salt);
+    // Defaults
+    var iterations = options && options.iterations || 1;
+
+    // Pseudo-random function
+    function PRF(password, salt) {
+        var j = new jssha(salt.toString('hex'), 'HEX');
+        var hash = j.getHMAC(password.toString('hex'), "HEX", "SHA-512", "HEX");
+        return new Buffer(hash, 'hex');
+    }
+
+    // Generate key
+    var derivedKeyBytes = new Buffer([]),
+        blockindex = 1;
+    while (derivedKeyBytes.length < keylen) {
+        var block = PRF(password, salt.concat([0, 0, 0, blockindex]));
+        for (var u = block, i = 1; i < iterations; i++) {
+            u = PRF(password, u);
+            for (var j = 0; j < block.length; j++) block[j] ^= u[j];
+        }
+        derivedKeyBytes = derivedKeyBytes.concat(block);
+        blockindex++;
+    }
+
+    // Truncate excess bytes - TODO
+    //derivedKeyBytes.length = keylen;
+
+    return new Buffer(derivedKeyBytes);
+};
+
+exports.pbkdf2Sync_sha512 = function(password, salt, iterations, keylen) {
+    return pbkdf2_sha512(password, salt, keylen, {iterations: iterations});
+};
diff --git a/lib/cryptox.js b/lib/cryptox.js
index 240736c..7f382df 100644
--- a/lib/cryptox.js
+++ b/lib/cryptox.js
@@ -1,49 +1,5 @@
-// Crypto extensions
-//
-// PBKDF2 with SHA512
-
-var binding = require('bindings')('cryptox');
-
-exports.pbkdf2_sha512 = function(password, salt, iterations, keylen, callback) {
-      if (typeof callback !== 'function')
-              throw new Error('No callback provided to pbkdf2');
-
-        return pbkdf2_sha512(password, salt, iterations, keylen, callback);
-};
-
-
-exports.pbkdf2Sync_sha512 = function(password, salt, iterations, keylen) {
-      return pbkdf2_sha512(password, salt, iterations, keylen);
-};
-
-function toBuf(str, encoding) {
-    encoding = encoding || 'binary';
-      if (typeof str === 'string') {
-            if (encoding === 'buffer')
-                    encoding = 'binary';
-                str = new Buffer(str, encoding);
-                  }
-        return str;
-}
-
-function pbkdf2_sha512(password, salt, iterations, keylen, callback) {
-  password = toBuf(password);
-  salt = toBuf(salt);
-
-  if (exports.DEFAULT_ENCODING === 'buffer')
-    return binding.PBKDF2(password, salt, iterations, keylen, callback);
-
-  // at this point, we need to handle encodings.
-  var encoding = exports.DEFAULT_ENCODING;
-  if (callback) {
-    binding.PBKDF2_sha512(password, salt, iterations, keylen, function(er, ret) {
-      if (ret)
-        ret = ret.toString(encoding);
-      callback(er, ret);
-    });
-  } else {
-    var ret = binding.PBKDF2_sha512(password, salt, iterations, keylen);
-    //return ret.toString(encoding);
-    return ret;
-  }
+if (process.versions) {
+  module.exports = require('./node/cryptox');
+  return;
 }
+module.exports = require('./browser/cryptox');
diff --git a/lib/node/cryptox.js b/lib/node/cryptox.js
new file mode 100644
index 0000000..240736c
--- /dev/null
+++ b/lib/node/cryptox.js
@@ -0,0 +1,49 @@
+// Crypto extensions
+//
+// PBKDF2 with SHA512
+
+var binding = require('bindings')('cryptox');
+
+exports.pbkdf2_sha512 = function(password, salt, iterations, keylen, callback) {
+      if (typeof callback !== 'function')
+              throw new Error('No callback provided to pbkdf2');
+
+        return pbkdf2_sha512(password, salt, iterations, keylen, callback);
+};
+
+
+exports.pbkdf2Sync_sha512 = function(password, salt, iterations, keylen) {
+      return pbkdf2_sha512(password, salt, iterations, keylen);
+};
+
+function toBuf(str, encoding) {
+    encoding = encoding || 'binary';
+      if (typeof str === 'string') {
+            if (encoding === 'buffer')
+                    encoding = 'binary';
+                str = new Buffer(str, encoding);
+                  }
+        return str;
+}
+
+function pbkdf2_sha512(password, salt, iterations, keylen, callback) {
+  password = toBuf(password);
+  salt = toBuf(salt);
+
+  if (exports.DEFAULT_ENCODING === 'buffer')
+    return binding.PBKDF2(password, salt, iterations, keylen, callback);
+
+  // at this point, we need to handle encodings.
+  var encoding = exports.DEFAULT_ENCODING;
+  if (callback) {
+    binding.PBKDF2_sha512(password, salt, iterations, keylen, function(er, ret) {
+      if (ret)
+        ret = ret.toString(encoding);
+      callback(er, ret);
+    });
+  } else {
+    var ret = binding.PBKDF2_sha512(password, salt, iterations, keylen);
+    //return ret.toString(encoding);
+    return ret;
+  }
+}
diff --git a/test/index.html b/test/index.html
index 7e036ce..c0bab93 100644
--- a/test/index.html
+++ b/test/index.html
@@ -20,6 +20,7 @@
     <script src="test.basic.js"></script>
     <script src="test.Bignum.browser.js"></script>
     <script src="test.BIP32.js"></script>
+    <script src="test.BIP39.js"></script>
     <script src="test.Block.js"></script>
     <script src="test.Bloom.js"></script>
     <script src="test.Connection.js"></script>
diff --git a/test/test.BIP39.js b/test/test.BIP39.js
index 0f8d810..03118ec 100644
--- a/test/test.BIP39.js
+++ b/test/test.BIP39.js
@@ -154,7 +154,7 @@ describe('BIP39', function() {
         var mnemonic1 = BIP39.to_mnemonic(BIP39WordlistEn, new Buffer(code, 'hex'));
         var seed1 = BIP39.mnemonic_to_seed(mnemonic, 'TREZOR');
         mnemonic1.should.equal(mnemonic);
-        seed1.toString().should.equal(new Buffer(seed, 'hex').toString());
+        seed1.toString('hex').should.equal(seed)
       }
     });
   });