diff --git a/README.md b/README.md
index cf83197..7061a70 100755
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 <img align="right" src="https://raw.github.com/hueniverse/hawk/master/images/logo.png" /> **Hawk** is an HTTP authentication scheme using a message authentication code (MAC) algorithm to provide partial
 HTTP request cryptographic verification. For more complex use cases such as access delegation, see [Oz](https://github.com/hueniverse/oz).
 
-Current version: **0.12**
+Current version: **0.13**
 
 [![Build Status](https://secure.travis-ci.org/hueniverse/hawk.png)](http://travis-ci.org/hueniverse/hawk)
 
@@ -345,10 +345,16 @@ Server-Authorization: Hawk mac="XIJRsMl/4oL+nn+vKoeVZPdCHXB4yJkNnBbTbHFZUYE=", h
 
 ## Browser Support and Considerations
 
-An experimental browser script is provided for including using a `<script>` tag in [lib/browser.js](/lib/browser.js).
+A browser script is provided for including using a `<script>` tag in [lib/browser.js](/lib/browser.js).
 
-**Hawk** relies on the _Server-Authorization_ and _WWW-Authenticate_ headers in its response to communicate with the client. Therefore, in case of CORS requests, it is important to consider sending _Access-Control-Expose-Headers_ with the value _"WWW-Authenticate, Server-Authorization"_ on each response from your server. As explained in the [specifications](http://www.w3.org/TR/cors/#access-control-expose-headers-response-header), it will indicate that these headers can safely be accessed by the client (using getResponseHeader() on the XmlHttpRequest object). Otherwise you will be met with a ["simple response header"](http://www.w3.org/TR/cors/#simple-response-header) which excludes these fields and would prevent the Hawk client from authenticating the requests.
-You can read more about the why and how in this [article](http://www.html5rocks.com/en/tutorials/cors/#toc-adding-cors-support-to-the-server)
+**Hawk** relies on the _Server-Authorization_ and _WWW-Authenticate_ headers in its response to communicate with the client.
+Therefore, in case of CORS requests, it is important to consider sending _Access-Control-Expose-Headers_ with the value
+_"WWW-Authenticate, Server-Authorization"_ on each response from your server. As explained in the
+[specifications](http://www.w3.org/TR/cors/#access-control-expose-headers-response-header), it will indicate that these headers
+can safely be accessed by the client (using getResponseHeader() on the XmlHttpRequest object). Otherwise you will be met with a
+["simple response header"](http://www.w3.org/TR/cors/#simple-response-header) which excludes these fields and would prevent the
+Hawk client from authenticating the requests.You can read more about the why and how in this
+[article](http://www.html5rocks.com/en/tutorials/cors/#toc-adding-cors-support-to-the-server)
 
 
 # Single URI Authorization
diff --git a/lib/browser.js b/lib/browser.js
index 8d12284..032c859 100755
--- a/lib/browser.js
+++ b/lib/browser.js
@@ -111,7 +111,7 @@ hawk.client = {
         if (!artifacts.hash &&
             options.hasOwnProperty('payload')) {
 
-            artifacts.hash = hawk.crypto.calculateHash(options.payload, credentials.algorithm, options.contentType);
+            artifacts.hash = hawk.crypto.calculatePayloadHash(options.payload, credentials.algorithm, options.contentType);
         }
 
         var mac = hawk.crypto.calculateMac('header', credentials, artifacts);
@@ -210,7 +210,7 @@ hawk.client = {
             return false;
         }
 
-        var calculatedHash = hawk.crypto.calculateHash(options.payload, credentials.algorithm, request.getResponseHeader('content-type'));
+        var calculatedHash = hawk.crypto.calculatePayloadHash(options.payload, credentials.algorithm, request.getResponseHeader('content-type'));
         return (calculatedHash === attributes.hash);
     }
 };
@@ -255,7 +255,7 @@ hawk.crypto = {
         return normalized;
     },
 
-    calculateHash: function (payload, algorithm, contentType) {
+    calculatePayloadHash: function (payload, algorithm, contentType) {
 
         var hash = CryptoJS.algo[algorithm.toUpperCase()].create();
         hash.update('hawk.' + hawk.crypto.headerVersion + '.payload\n');
@@ -275,41 +275,38 @@ hawk.crypto = {
 
 hawk.utils = {
 
-    ntpOffset: 0,
+    storage: {                                      // localStorage compatible interface
+        _cache: {},
+        setItem: function (key, value) {
 
-    storage: false,
-
-    useLocalStorage: function (storage) {
-
-        hawk.utils.storage = storage;
+            hawk.utils.storage._cache[key] = value;
+        },
+        getItem: function (key) {
 
-        if (hawk.utils.storage) {
-            hawk.utils.ntpOffset = hawk.utils.getLocalNtpOffset();
+            return hawk.utils.storage._cache[key];
         }
     },
 
-    setLocalNtpOffset: function (offset) {
+    setStorage: function (storage) {
 
-        hawk.utils.storage.setItem('hawk_ntp_offset', offset);
+        var ntpOffset = hawk.utils.getNtpOffset() || 0;
+        hawk.utils.storage = storage;
+        hawk.utils.setNtpOffset(ntpOffset);
     },
 
-    getLocalNtpOffset: function () {
+    setNtpOffset: function (offset) {
 
-        return hawk.utils.storage.getItem('hawk_ntp_offset');
+        hawk.utils.storage.setItem('hawk_ntp_offset', offset);
     },
 
-    setNtpOffset: function (offset) {
-
-        hawk.utils.ntpOffset = offset;
+    getNtpOffset: function () {
 
-        if (hawk.utils.storage) {
-            hawk.utils.setLocalNtpOffset(offset);
-        }
+        return parseInt(hawk.utils.storage.getItem('hawk_ntp_offset') || '0', 10);
     },
 
     now: function () {
 
-        return Date.now() + hawk.utils.ntpOffset;
+        return Date.now() + hawk.utils.getNtpOffset();
     },
 
     escapeHeaderAttribute: function (attribute) {
@@ -421,14 +418,6 @@ hawk.utils = {
 };
 
 
-try {
-    hawk.utils.useLocalStorage(localStorage)
-}
-catch (err) {
-    // localStorage not used
-}
-
-
 // Based on: Crypto-JS v3.1.2
 // Copyright (c) 2009-2013, Jeff Mott. All rights reserved.
 // http://code.google.com/p/crypto-js/
diff --git a/lib/client.js b/lib/client.js
index ea54250..492aa4f 100755
--- a/lib/client.js
+++ b/lib/client.js
@@ -105,7 +105,7 @@ exports.header = function (uri, method, options) {
     if (!artifacts.hash &&
         options.hasOwnProperty('payload')) {
 
-        artifacts.hash = Crypto.calculateHash(options.payload, credentials.algorithm, options.contentType);
+        artifacts.hash = Crypto.calculatePayloadHash(options.payload, credentials.algorithm, options.contentType);
     }
 
     var mac = Crypto.calculateMac('header', credentials, artifacts);
@@ -193,7 +193,7 @@ exports.authenticate = function (res, credentials, artifacts, options) {
         return false;
     }
 
-    var calculatedHash = Crypto.calculateHash(options.payload, credentials.algorithm, res.headers['content-type']);
+    var calculatedHash = Crypto.calculatePayloadHash(options.payload, credentials.algorithm, res.headers['content-type']);
     return (calculatedHash === attributes.hash);
 };
 
diff --git a/lib/crypto.js b/lib/crypto.js
index c4c3d5e..7e66725 100755
--- a/lib/crypto.js
+++ b/lib/crypto.js
@@ -78,12 +78,25 @@ exports.generateNormalizedString = function (type, options) {
 };
 
 
-exports.calculateHash = function (payload, algorithm, contentType) {
+exports.calculatePayloadHash = function (payload, algorithm, contentType) {
+
+    var hash = exports.createPayloadHash(algorithm, contentType);
+    hash.update(payload || '');
+    return exports.finalizePayloadHash(hash);
+};
+
+
+exports.createPayloadHash = function (algorithm, contentType) {
 
     var hash = Crypto.createHash(algorithm);
     hash.update('hawk.' + exports.headerVersion + '.payload\n');
     hash.update(Utils.parseContentType(contentType) + '\n');
-    hash.update(payload || '');
+    return hash;
+};
+
+
+exports.finalizePayloadHash = function (hash) {
+
     hash.update('\n');
     return hash.digest('base64');
 };
diff --git a/lib/server.js b/lib/server.js
index fdf0371..4d7a832 100755
--- a/lib/server.js
+++ b/lib/server.js
@@ -171,7 +171,7 @@ exports.authenticate = function (req, credentialsFunc, options, callback) {
                 return callback(Boom.unauthorized('Missing required payload hash', 'Hawk'), credentials, artifacts);
             }
 
-            var hash = Crypto.calculateHash(options.payload, credentials.algorithm, request.contentType);
+            var hash = Crypto.calculatePayloadHash(options.payload, credentials.algorithm, request.contentType);
             if (!Cryptiles.fixedTimeComparison(hash, attributes.hash)) {
                 return callback(Boom.unauthorized('Bad payload hash', 'Hawk'), credentials, artifacts);
             }
@@ -212,7 +212,7 @@ exports.authenticate = function (req, credentialsFunc, options, callback) {
 
 exports.authenticatePayload = function (payload, credentials, artifacts, contentType) {
 
-    var calculatedHash = Crypto.calculateHash(payload, credentials.algorithm, contentType);
+    var calculatedHash = Crypto.calculatePayloadHash(payload, credentials.algorithm, contentType);
     return Cryptiles.fixedTimeComparison(calculatedHash, artifacts.hash);
 };
 
@@ -267,7 +267,7 @@ exports.header = function (credentials, artifacts, options) {
     if (!artifacts.hash &&
         options.hasOwnProperty('payload')) {
 
-        artifacts.hash = Crypto.calculateHash(options.payload, credentials.algorithm, options.contentType);
+        artifacts.hash = Crypto.calculatePayloadHash(options.payload, credentials.algorithm, options.contentType);
     }
 
     var mac = Crypto.calculateMac('response', credentials, artifacts);
diff --git a/package.json b/package.json
index 9c42cd6..4d5f59f 100755
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "hawk",
   "description": "HTTP Hawk Authentication Scheme",
-  "version": "0.12.2",
+  "version": "0.13.0",
   "author": "Eran Hammer <eran@hueniverse.com> (http://hueniverse.com)",
   "contributors": [],
   "repository": "git://github.com/hueniverse/hawk",
diff --git a/test/browser.js b/test/browser.js
index 378a563..323cfbe 100755
--- a/test/browser.js
+++ b/test/browser.js
@@ -197,7 +197,56 @@ describe('Browser', function () {
         };
 
         credentialsFunc('123456', function (err, credentials) {
-            Browser.utils.useLocalStorage(LocalStorage)
+
+            Browser.utils.setNtpOffset(60 * 60 * 1000);
+            var header = Browser.client.header('http://example.com:8080/resource/4?filter=a', req.method, { credentials: credentials, ext: 'some-app-data' });
+            req.authorization = header.field;
+            expect(req.authorization).to.exist;
+
+            Hawk.server.authenticate(req, credentialsFunc, {}, function (err, credentials, artifacts) {
+
+                expect(err).to.exist;
+                expect(err.message).to.equal('Stale timestamp');
+
+                var res = {
+                    headers: {
+                        'www-authenticate': err.response.headers['WWW-Authenticate']
+                    },
+                    getResponseHeader: function (header) {
+
+                        return res.headers[header.toLowerCase()];
+                    }
+                };
+
+                expect(Browser.utils.getNtpOffset()).to.equal(60 * 60 * 1000);
+                expect(Browser.client.authenticate(res, credentials, header.artifacts)).to.equal(true);
+                expect(Browser.utils.getNtpOffset()).to.equal(0);
+
+                req.authorization = Browser.client.header('http://example.com:8080/resource/4?filter=a', req.method, { credentials: credentials, ext: 'some-app-data' }).field;
+                expect(req.authorization).to.exist;
+
+                Hawk.server.authenticate(req, credentialsFunc, {}, function (err, credentials, artifacts) {
+
+                    expect(err).to.not.exist;
+                    expect(credentials.user).to.equal('steve');
+                    expect(artifacts.ext).to.equal('some-app-data');
+                    done();
+                });
+            });
+        });
+    });
+
+    it('should generate a header with stale ts and successfully authenticate on second call (manual localStorage)', function (done) {
+
+        var req = {
+            method: 'GET',
+            url: '/resource/4?filter=a',
+            host: 'example.com',
+            port: 8080
+        };
+
+        credentialsFunc('123456', function (err, credentials) {
+            Browser.utils.setStorage(LocalStorage)
 
             Browser.utils.setNtpOffset(60 * 60 * 1000);
             var header = Browser.client.header('http://example.com:8080/resource/4?filter=a', req.method, { credentials: credentials, ext: 'some-app-data' });
@@ -220,9 +269,9 @@ describe('Browser', function () {
                 };
 
                 expect(parseInt(LocalStorage.getItem('hawk_ntp_offset'))).to.equal(60 * 60 * 1000);
-                expect(Browser.utils.ntpOffset).to.equal(60 * 60 * 1000);
+                expect(Browser.utils.getNtpOffset()).to.equal(60 * 60 * 1000);
                 expect(Browser.client.authenticate(res, credentials, header.artifacts)).to.equal(true);
-                expect(Browser.utils.ntpOffset).to.equal(0);
+                expect(Browser.utils.getNtpOffset()).to.equal(0);
                 expect(parseInt(LocalStorage.getItem('hawk_ntp_offset'))).to.equal(0);
 
                 req.authorization = Browser.client.header('http://example.com:8080/resource/4?filter=a', req.method, { credentials: credentials, ext: 'some-app-data' }).field;
diff --git a/test/readme.js b/test/readme.js
index 4c9c44b..f39e033 100755
--- a/test/readme.js
+++ b/test/readme.js
@@ -85,7 +85,7 @@ describe('Hawk', function () {
                     resource: '/resource?a=1&b=2',
                     host: 'example.com',
                     port: 8000,
-                    hash: Hawk.crypto.calculateHash(payloadOptions.payload, credentials.algorithm, payloadOptions.contentType),
+                    hash: Hawk.crypto.calculatePayloadHash(payloadOptions.payload, credentials.algorithm, payloadOptions.contentType),
                     ext: options.ext
                 });