diff --git a/README.md b/README.md
index eb7ba62..8c75ce6 100755
--- a/README.md
+++ b/README.md
@@ -6,15 +6,19 @@
 
 JSON Web Token authentication requires verifying a signed token. The `'jwt'` scheme takes the following options:
 
-- `key` - (required) The private key the token was signed with.
-- `validateFunc` - (optional) validation and user lookup function with the signature `function(token, callback)` where:
+- `key` - (required) Either the private key the token was signed with or a key lookup function with signature `function(token, callback)` where:
+    - `token` - the *unverified* encoded jwt token
+    - `callback` - a callback function with the signature `function(err, key, extraInfo)` where:
+        - `err` - an internal error
+        - `key` - the private key that will be used to verify the token
+        - `extraInfo` - data that will be passed to `validateFunc` (e.g. credentials)
+- `validateFunc` - (optional) validation and user lookup function with the signature `function(token, extraInfo, callback)` where:
     - `token` - the verified and decoded jwt token
+    - `extraInfo` - data that was passed from the key lookup function (e.g. credentials)
     - `callback` - a callback function with the signature `function(err, isValid, credentials)` where:
         - `err` - an internal error.
         - `isValid` - `true` if the token was valid otherwise `false`.
-        - `credentials` - a credentials object passed back to the application in `request.auth.credentials`. Typically, `credentials` are only
-          included when `isValid` is `true`, but there are cases when the application needs to know who tried to authenticate even when it fails
-          (e.g. with authentication mode `'try'`).
+        - `credentials` - a credentials object passed back to the application in `request.auth.credentials`. Typically, `credentials` are only included when `isValid` is `true`, but there are cases when the application needs to know who tried to authenticate even when it fails (e.g. with authentication mode `'try'`).
 
 See the example folder for an executable example.
 
@@ -26,7 +30,6 @@ var Hapi = require('hapi'),
 
 server.connection({ port: 8080 });
 
-
 var accounts = {
     123: {
         id: 123,
@@ -36,7 +39,6 @@ var accounts = {
     }
 };
 
-
 var privateKey = 'BbZJjyoXAdr8BUZuiKKARWimKfrSmQ6fv8kZ7OFfc';
 
 // Use this token to build your request with the 'Authorization' header.  
@@ -44,8 +46,7 @@ var privateKey = 'BbZJjyoXAdr8BUZuiKKARWimKfrSmQ6fv8kZ7OFfc';
 //     Authorization: Bearer <token>
 var token = jwt.sign({ accountId: 123 }, privateKey);
 
-
-var validate = function (decodedToken, callback) {
+var validate = function (decodedToken, extraInfo, callback) {
 
     var error,
         credentials = accounts[decodedToken.accountId] || {};
@@ -57,7 +58,6 @@ var validate = function (decodedToken, callback) {
     return callback(error, true, credentials)
 };
 
-
 server.register(require('hapi-auth-jwt'), function (error) {
 
     server.auth.strategy('token', 'jwt', {
@@ -86,6 +86,89 @@ server.register(require('hapi-auth-jwt'), function (error) {
     });
 });
 
+server.start();
+
+```
+
+With a key lookup method:
+
+```javascript
+
+var Hapi = require('hapi'),
+    jwt = require('jsonwebtoken'),
+    server = new Hapi.Server();
+
+server.connection({ port: 8080 });
+
+var accounts = {
+    123: {
+        id: 123,
+        user: 'john',
+        fullName: 'John Doe',
+        privateKey: 'BbZJjyoXAdr8BUZuiKKARWimKfrSmQ6fv8kZ7OFfc'
+        scope: ['a', 'b']
+    }
+};
+
+var getKey = function(token, callback) {
+  var data = jwt.decode(token);
+  var account = accounts[data.id];
+  var key = account.privateKey;
+
+  var credentials = {
+    id: account.id,
+    user: account.user
+    fullName: account.fullName,
+    scope: account.scope
+  }
+
+  callback(null, key, credentials);
+}
+
+// Use this token to build your request with the 'Authorization' header.  
+// Ex:
+//     Authorization: Bearer <token>
+var token = jwt.sign({ accountId: 123 }, privateKey);
+
+var validate = function (decodedToken, extraInfo, callback) {
+
+    var error,
+        credentials = extraInfo || {};
+
+    if (!credentials) {
+        return callback(error, false, credentials);
+    }
+
+    return callback(error, true, credentials)
+};
+
+server.register(require('hapi-auth-jwt'), function (error) {
+
+    server.auth.strategy('token', 'jwt', {
+        key: getKey,
+        validateFunc: validate
+    });
+
+    server.route({
+        method: 'GET',
+        path: '/',
+        config: {
+            auth: 'token'
+        }
+    });
+
+    // With scope requirements
+    server.route({
+        method: 'GET',
+        path: '/withScope',
+        config: {
+            auth: {
+                strategy: 'token',
+                scope: ['a']
+            }
+        }
+    });
+});
 
 server.start();
 
diff --git a/lib/index.js b/lib/index.js
index 396bdaa..5f56b76 100755
--- a/lib/index.js
+++ b/lib/index.js
@@ -20,6 +20,9 @@ exports.register.attributes = {
     pkg: require('../package.json')
 };
 
+function isFunction(functionToCheck) {
+  return Object.prototype.toString.call(functionToCheck) === '[object Function]';
+}
 
 internals.implementation = function (server, options) {
 
@@ -53,42 +56,49 @@ internals.implementation = function (server, options) {
 
       var token = parts[1];
 
-      jwt.verify(token, settings.key, function(err, decoded) {
-        if(err && err.message === 'jwt expired') {
-          return reply(Boom.unauthorized('Expired token received for JSON Web Token validation', 'Bearer'));
-        } else if (err) {
-          return reply(Boom.unauthorized('Invalid signature received for JSON Web Token validation', 'Bearer'));
-        }
+      var getKey = isFunction(settings.key) ?
+        settings.key :
+        function(token, callback) { callback(null, settings.key); };
 
-        if (!settings.validateFunc) {
-          return reply.continue({ credentials: decoded });
-        }
+      getKey(token, function(err, key, extraInfo){
+        if (err) { return reply(Boom.wrap(err)); }
 
+        // handle err
+        jwt.verify(token, key, function(err, decoded) {
+          if(err && err.message === 'jwt expired') {
+            return reply(Boom.unauthorized('Expired token received for JSON Web Token validation', 'Bearer'));
+          } else if (err) {
+            return reply(Boom.unauthorized('Invalid signature received for JSON Web Token validation', 'Bearer'));
+          }
 
-        settings.validateFunc(decoded, function (err, isValid, credentials) {
+          if (!settings.validateFunc) {
+            return reply.continue({ credentials: decoded });
+          }
 
-          credentials = credentials || null;
+          settings.validateFunc(decoded, extraInfo, function (err, isValid, credentials) {
 
-          if (err) {
-            return reply(err, null, { credentials: credentials });
-          }
+            credentials = credentials || null;
 
-          if (!isValid) {
-            return reply(Boom.unauthorized('Invalid token', 'Bearer'), null, { credentials: credentials });
-          }
+            if (err) {
+              return reply(err, null, { credentials: credentials, log: { tags: ['auth', 'jwt'], data: err } });
+            }
 
-          if (!credentials || typeof credentials !== 'object') {
+            if (!isValid) {
+              return reply(Boom.unauthorized('Invalid token', 'Bearer'), null, { credentials: credentials });
+            }
 
-            return reply(Boom.badImplementation('Bad credentials object received for jwt auth validation'), null, { log: { tags: 'credentials' } });
-          }
+            if (!credentials || typeof credentials !== 'object') {
 
-          // Authenticated
+              return reply(Boom.badImplementation('Bad credentials object received for jwt auth validation'), null, { log: { tags: 'credentials' } });
+            }
 
-          return reply.continue({ credentials: credentials });
-        });
+            // Authenticated
 
-      });
+            return reply.continue({ credentials: credentials });
+          });
 
+        });
+      });
     }
   };
 
diff --git a/package.json b/package.json
index 0db84a1..374fe50 100755
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "hapi-auth-jwt",
   "description": "JSON Web Token (JWT) authentication plugin",
-  "version": "2.1.0",
+  "version": "2.1.1",
   "author": "Ryan Fitzgerald <ryan.fitz1@gmail.com>",
   "repository": "git://github.com/ryanfitz/hapi-auth-jwt",
   "main": "index",
@@ -17,7 +17,7 @@
   "dependencies": {
     "boom": "2.x.x",
     "hoek": "2.x.x",
-    "jsonwebtoken": "3.2.x"
+    "jsonwebtoken": "^4.2.0"
   },
   "peerDependencies": {
     "hapi": ">=8.x.x"
diff --git a/test/dynamicKeys.tests.js b/test/dynamicKeys.tests.js
new file mode 100644
index 0000000..260290e
--- /dev/null
+++ b/test/dynamicKeys.tests.js
@@ -0,0 +1,142 @@
+// Load modules
+
+var Lab  = require('lab');
+var Hapi = require('hapi');
+var Code = require('code');
+var Hoek = require('hoek')
+var Boom = require('boom');
+var jwt  = require('jsonwebtoken');
+
+
+// Test shortcuts
+
+var lab = exports.lab = Lab.script();
+var expect = Code.expect;
+var before = lab.before;
+var describe = lab.describe;
+var it = lab.it;
+
+describe('Dynamic Secret', function () {
+  var keys = {
+    'john': 'johnkey',
+    'jane': 'janekey'
+  };
+
+  var info = {
+    'john': 'johninfo',
+    'jane': 'janeinfo',
+  }
+
+  var tokenHeader = function (username, options) {
+    if (!keys[username]){
+      throw new Error('Invalid user name ' + username + '. Valid options \'john\' or \'jane\'');
+    }
+
+    options = options || {};
+
+    return 'Bearer ' + jwt.sign({username: username}, keys[username], options);
+  };
+
+  var tokenHandler = function (request, reply) {
+    reply(request.auth.credentials.username);
+  };
+
+  var getKey = function(token, callback){
+    getKey.lastToken = token;
+    var data = jwt.decode(token);
+    Hoek.nextTick(function(){
+      callback(null, keys[data.username], info[data.username]);
+    })();
+  }
+
+  var validateFunc = function(decoded, extraInfo, callback){
+    validateFunc.lastExtraInfo = extraInfo;
+    callback(null, true, decoded);
+  }
+
+  var errorGetKey = function(token, callback){
+    callback(new Error('Failed'));
+  }
+
+  var boomErrorGetKey = function(token, callback){
+    callback(Boom.forbidden('forbidden'));
+  }
+
+  var server = new Hapi.Server({ debug: false });
+  server.connection();
+
+  before(function (done) {
+    server.register(require('../'), function (err) {
+      expect(err).to.not.exist;
+      server.auth.strategy('normalError', 'jwt', false, { key: errorGetKey });
+      server.auth.strategy('boomError', 'jwt', false, { key: boomErrorGetKey });
+      server.auth.strategy('default', 'jwt', false, { key: getKey, validateFunc: validateFunc });
+      server.route([
+        { method: 'POST', path: '/token', handler: tokenHandler, config: { auth: 'default' } },
+        { method: 'POST', path: '/normalError', handler: tokenHandler, config: { auth: 'normalError' } },
+        { method: 'POST', path: '/boomError', handler: tokenHandler, config: { auth: 'boomError' } }
+      ]);
+
+      done();
+    });
+  });
+
+  ['jane', 'john'].forEach(function(user){
+
+    it('uses key function passing ' + user + '\'s token if ' + user + ' is user', function (done) {
+
+      var request = { method: 'POST', url: '/token', headers: { authorization: tokenHeader(user) } };
+
+      server.inject(request, function (res) {
+        expect(res.result).to.exist;
+        expect(res.result).to.equal(user);
+
+        jwt.verify(getKey.lastToken, keys[user], function(err, decoded){
+          if (err) { return done(err); }
+          expect(decoded.username).to.equal(user);
+
+          done();
+        });
+      });
+    });
+
+    it('uses validateFunc function passing ' + user + '\'s extra info if ' + user + ' is user', function (done) {
+
+      var request = { method: 'POST', url: '/token', headers: { authorization: tokenHeader(user) } };
+
+      server.inject(request, function (res) {
+        expect(res.result).to.exist;
+        expect(res.result).to.equal(user);
+
+        expect(validateFunc.lastExtraInfo).to.equal(info[user]);
+        done();
+      });
+    });
+  });
+
+  it('return 500 if an is error thrown when getting key', function(done){
+
+    var request = { method: 'POST', url: '/normalError', headers: { authorization: tokenHeader('john') } };
+
+    server.inject(request, function (res) {
+      expect(res).to.exist;
+      expect(res.result.statusCode).to.equal(500);
+      expect(res.result.error).to.equal('Internal Server Error');
+      expect(res.result.message).to.equal('An internal server error occurred');
+      done();
+    });
+  });
+
+  it('return 403 if an is error thrown when getting key', function(done){
+
+    var request = { method: 'POST', url: '/boomError', headers: { authorization: tokenHeader('john') } };
+
+    server.inject(request, function (res) {
+      expect(res).to.exist;
+      expect(res.result.statusCode).to.equal(403);
+      expect(res.result.error).to.equal('Forbidden');
+      expect(res.result.message).to.equal('forbidden');
+      done();
+    });
+  });
+});
\ No newline at end of file
diff --git a/test/index.js b/test/index.js
index 4d2e5a4..0810047 100755
--- a/test/index.js
+++ b/test/index.js
@@ -24,7 +24,7 @@ describe('Token', function () {
     return 'Bearer ' + Jwt.sign({username : username}, privateKey, options);
   };
 
-  var loadUser = function (decodedToken, callback) {
+  var loadUser = function (decodedToken, _, callback) {
     var username = decodedToken.username;
 
     if (username === 'john') {