diff --git a/websocket-sharp.userprefs b/websocket-sharp.userprefs
index 95d21ed1..1810154c 100644
--- a/websocket-sharp.userprefs
+++ b/websocket-sharp.userprefs
@@ -1,8 +1,8 @@
 <Properties>
-  <MonoDevelop.Ide.Workspace ActiveConfiguration="Release_Ubuntu" ctype="Workspace" />
+  <MonoDevelop.Ide.Workspace ActiveConfiguration="Debug_Ubuntu" ctype="Workspace" />
   <MonoDevelop.Ide.Workbench ActiveDocument="websocket-sharp/WebSocket.cs" ctype="Workbench">
     <Files>
-      <File FileName="websocket-sharp/WebSocket.cs" Line="1" Column="1" />
+      <File FileName="websocket-sharp/WebSocket.cs" Line="264" Column="15" />
     </Files>
   </MonoDevelop.Ide.Workbench>
   <MonoDevelop.Ide.DebuggingService.Breakpoints>
diff --git a/websocket-sharp/Ext.cs b/websocket-sharp/Ext.cs
index 901ccaeb..c5cb5172 100644
--- a/websocket-sharp/Ext.cs
+++ b/websocket-sharp/Ext.cs
@@ -28,6 +28,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace WebSocketSharp
 {
@@ -40,11 +41,91 @@ namespace WebSocketSharp
       return b == Convert.ToByte(c);
     }
 
-    public static void NotEqualsDo(this string a, string b, Action<string> action)
+    public static uint GenerateKey(this Random rand, int space)
+    {
+      uint max = (uint)(0xffffffff / space);
+
+      int upper16 = (int)((max & 0xffff0000) >> 16);
+      int lower16 = (int)(max & 0x0000ffff);
+
+      return ((uint)rand.Next(upper16 + 1) << 16) + (uint)rand.Next(lower16 + 1);
+    }
+
+    public static string GenerateSecKey(this Random rand, out uint key)
+    {
+      int space = rand.Next(1, 13);
+      int ascii = rand.Next(1, 13);
+
+      key = rand.GenerateKey(space);
+
+      long mKey = key * space;
+      char[] mKeyChars = mKey.ToString().ToCharArray();
+      int mKeyCharsLen = mKeyChars.Length;
+
+      int secKeyCharsLen = mKeyCharsLen + space + ascii;
+      char[] secKeyChars = new char[secKeyCharsLen].InitializeWith(' ');
+
+      secKeyChars[0] = mKeyChars[0];
+      secKeyChars[secKeyCharsLen - 1] = mKeyChars[mKeyCharsLen - 1];
+
+      int i = 0;
+      for (int j = 1; j < mKeyCharsLen - 1; j++)
+      {
+        i = rand.Next(i + 1, secKeyCharsLen - mKeyCharsLen + j + 1);
+        secKeyChars[i] = mKeyChars[j];
+      }
+
+      var convToAscii = secKeyChars
+                        .IndexOf(' ')
+                        .OrderBy( x => Guid.NewGuid() )
+                        .Where( (x, idx) => idx < ascii );
+
+      int k; 
+      foreach (int index in convToAscii)
+      {
+        k = rand.Next(2) == 0 ? rand.Next(33, 48) : rand.Next(58, 127);
+        secKeyChars[index] = Convert.ToChar(k);
+      }
+
+      return new String(secKeyChars);
+    }
+
+    public static IEnumerable<int> IndexOf<T>(this T[] array, T val)
+    {
+      for (int i = 0; i < array.Length; i++)
+      {
+        if (array[i].Equals(val))
+        {
+          yield return i;
+        }
+      }
+    }
+
+    public static T[] InitializeWith<T>(this T[] array, T val)
+    {
+      for (int i = 0; i < array.Length; i++)
+      {
+        array[i] = val;
+      }
+
+      return array;
+    }
+
+    public static Byte[] InitializeWithASCII(this Byte[] bytes, Random rand)
+    {
+      for (int i = 0; i < bytes.Length; i++)  
+      {  
+        bytes[i] = (byte)rand.Next(32, 127);
+      }  
+  
+      return bytes;  
+    }
+
+    public static void NotEqualsDo(this string a, string b, Action<string, string> action)
     {
       if (a != b)
       {
-        action(a);
+        action(a, b);
       }
     }
   }
diff --git a/websocket-sharp/WebSocket.cs b/websocket-sharp/WebSocket.cs
index c72a8743..d17b863e 100644
--- a/websocket-sharp/WebSocket.cs
+++ b/websocket-sharp/WebSocket.cs
@@ -33,11 +33,13 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Net;
 using System.Net.Security;
 using System.Net.Sockets;
 using System.Text;
 using System.Threading;
+using System.Security.Cryptography;
 
 namespace WebSocketSharp
 {
@@ -256,17 +258,39 @@ namespace WebSocketSharp
         host += ":" + port;
       }
 
-      string subprotocol = protocol != String.Empty
+      string subProtocol = protocol != String.Empty
                            ? String.Format("Sec-WebSocket-Protocol: {0}\r\n", protocol)
                            : protocol;
+#if !CHALLENGE
+      string secKeys = String.Empty;
+      string key3AsASCII = String.Empty;
+#else
+      Random rand = new Random();
 
+      uint key1, key2;
+      string secKey1 = rand.GenerateSecKey(out key1);
+      string secKey2 = rand.GenerateSecKey(out key2);
+
+      byte[] key3 = new byte[8].InitializeWithASCII(rand);
+
+      string secKeys = "Sec-WebSocket-Key1: {0}\r\n" +
+                       "Sec-WebSocket-Key2: {1}\r\n";
+      secKeys = String.Format(secKeys, secKey1, secKey2);
+
+      string key3AsASCII = Encoding.ASCII.GetString(key3);
+
+      byte[] expectedRes = createExpectedRes(key1, key2, key3);
+      byte[] actualRes = new byte[16];
+#endif
       string request = "GET " + path + " HTTP/1.1\r\n" +
                        "Upgrade: WebSocket\r\n" +
                        "Connection: Upgrade\r\n" +
-                       subprotocol +
+                       subProtocol +
                        "Host: " + host + "\r\n" +
                        "Origin: " + origin + "\r\n" +
-                       "\r\n";
+                       secKeys +
+                       "\r\n" +
+                       key3AsASCII;
 #if DEBUG
       Console.WriteLine("WS: Info @doHandshake: Handshake from client: \n{0}", request);
 #endif
@@ -283,6 +307,10 @@ namespace WebSocketSharp
             wsStream.ReadByte().EqualsWithSaveTo('\r', rawdata) &&
             wsStream.ReadByte().EqualsWithSaveTo('\n', rawdata))
         {
+#if CHALLENGE
+          wsStream.Read(actualRes, 0, actualRes.Length);
+          rawdata.AddRange(actualRes);
+#endif
           break;
         }
       }
@@ -297,15 +325,25 @@ namespace WebSocketSharp
         Console.WriteLine("{0}", s);
       }
 #endif
-      Action<string> action = s => { throw new IOException("Invalid handshake response: " + s); };
+      Action<string, string> action = (a, b) =>
+      { 
+        throw new IOException("Invalid handshake response: " + a);
+      };
+#if !CHALLENGE
       response[0].NotEqualsDo("HTTP/1.1 101 Web Socket Protocol Handshake", action);
+#else
+      response[0].NotEqualsDo("HTTP/1.1 101 WebSocket Protocol Handshake", action);
+#endif
       response[1].NotEqualsDo("Upgrade: WebSocket", action);
       response[2].NotEqualsDo("Connection: Upgrade", action);
 
       for (int i = 3; i < response.Length; i++)
       {
+#if !CHALLENGE
         if (response[i].Contains("WebSocket-Protocol:"))
-//        if (response[i].Contains("Sec-WebSocket-Protocol:"))
+#else
+        if (response[i].Contains("Sec-WebSocket-Protocol:"))
+#endif
         {
           int j = response[i].IndexOf(":");
           protocol = response[i].Substring(j + 1).Trim();
@@ -315,10 +353,39 @@ namespace WebSocketSharp
 #if DEBUG
       Console.WriteLine("WS: Info @doHandshake: Sub protocol: {0}", protocol);
 #endif
+#if CHALLENGE
+      string expectedResHexStr = BitConverter.ToString(expectedRes);
+      string actualResHexStr = BitConverter.ToString(actualRes);
 
+      actualResHexStr.NotEqualsDo(expectedResHexStr, (a, b) =>
+        {
+          Console.WriteLine("WS: Error @doHandshake: Invalid challenge response.");
+          Console.WriteLine("\texpected: {0}", b);
+          Console.WriteLine("\tactual  : {0}", a);
+          throw new IOException("Invalid challenge response: " + a);
+        }
+      );
+  #if DEBUG
+      Console.WriteLine("WS: Info @doHandshake: challenge response: {0}", actualResHexStr);
+  #endif
+#endif
       ReadyState = WsState.OPEN;
     }
 
+    private byte[] createExpectedRes(uint key1, uint key2, byte[] key3)
+    {
+      byte[] key1Bytes = BitConverter.GetBytes(key1);
+      byte[] key2Bytes = BitConverter.GetBytes(key2);
+
+      Array.Reverse(key1Bytes);
+      Array.Reverse(key2Bytes);
+
+      byte[] concatKeys = key1Bytes.Concat(key2Bytes).Concat(key3).ToArray();
+
+      MD5 md5 = MD5.Create();
+      return md5.ComputeHash(concatKeys);
+    }
+
     private void message()
     {
 #if DEBUG
diff --git a/websocket-sharp/bin/Debug/websocket-sharp.dll b/websocket-sharp/bin/Debug/websocket-sharp.dll
index 2d822e8d..709ca57d 100755
Binary files a/websocket-sharp/bin/Debug/websocket-sharp.dll and b/websocket-sharp/bin/Debug/websocket-sharp.dll differ
diff --git a/websocket-sharp/bin/Debug/websocket-sharp.dll.mdb b/websocket-sharp/bin/Debug/websocket-sharp.dll.mdb
index c4d7b185..cc7980ce 100644
Binary files a/websocket-sharp/bin/Debug/websocket-sharp.dll.mdb and b/websocket-sharp/bin/Debug/websocket-sharp.dll.mdb differ
diff --git a/websocket-sharp/bin/Debug_Ubuntu/websocket-sharp.dll b/websocket-sharp/bin/Debug_Ubuntu/websocket-sharp.dll
index 5a8e6cd9..8af4fa1f 100755
Binary files a/websocket-sharp/bin/Debug_Ubuntu/websocket-sharp.dll and b/websocket-sharp/bin/Debug_Ubuntu/websocket-sharp.dll differ
diff --git a/websocket-sharp/bin/Debug_Ubuntu/websocket-sharp.dll.mdb b/websocket-sharp/bin/Debug_Ubuntu/websocket-sharp.dll.mdb
index aa91a37d..5f51c80e 100644
Binary files a/websocket-sharp/bin/Debug_Ubuntu/websocket-sharp.dll.mdb and b/websocket-sharp/bin/Debug_Ubuntu/websocket-sharp.dll.mdb differ
diff --git a/websocket-sharp/bin/Release/websocket-sharp.dll b/websocket-sharp/bin/Release/websocket-sharp.dll
index 012e365b..022c9957 100755
Binary files a/websocket-sharp/bin/Release/websocket-sharp.dll and b/websocket-sharp/bin/Release/websocket-sharp.dll differ
diff --git a/websocket-sharp/bin/Release_Ubuntu/websocket-sharp.dll b/websocket-sharp/bin/Release_Ubuntu/websocket-sharp.dll
index 3844a3cd..fa19e1b4 100755
Binary files a/websocket-sharp/bin/Release_Ubuntu/websocket-sharp.dll and b/websocket-sharp/bin/Release_Ubuntu/websocket-sharp.dll differ
diff --git a/websocket-sharp/websocket-sharp.csproj b/websocket-sharp/websocket-sharp.csproj
index 98f67fdc..ab6fb5c3 100644
--- a/websocket-sharp/websocket-sharp.csproj
+++ b/websocket-sharp/websocket-sharp.csproj
@@ -16,7 +16,7 @@
     <DebugType>full</DebugType>
     <Optimize>false</Optimize>
     <OutputPath>bin\Debug</OutputPath>
-    <DefineConstants>DEBUG</DefineConstants>
+    <DefineConstants>DEBUG,CHALLENGE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <ConsolePause>false</ConsolePause>
@@ -34,7 +34,7 @@
     <DebugType>full</DebugType>
     <Optimize>false</Optimize>
     <OutputPath>bin\Debug_Ubuntu</OutputPath>
-    <DefineConstants>DEBUG</DefineConstants>
+    <DefineConstants>DEBUG,CHALLENGE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <ConsolePause>false</ConsolePause>
diff --git a/websocket-sharp/websocket-sharp.pidb b/websocket-sharp/websocket-sharp.pidb
index a5553774..af744ce5 100644
Binary files a/websocket-sharp/websocket-sharp.pidb and b/websocket-sharp/websocket-sharp.pidb differ
diff --git a/wsclient/bin/Debug/websocket-sharp.dll b/wsclient/bin/Debug/websocket-sharp.dll
index 2d822e8d..709ca57d 100755
Binary files a/wsclient/bin/Debug/websocket-sharp.dll and b/wsclient/bin/Debug/websocket-sharp.dll differ
diff --git a/wsclient/bin/Debug/websocket-sharp.dll.mdb b/wsclient/bin/Debug/websocket-sharp.dll.mdb
index c4d7b185..cc7980ce 100644
Binary files a/wsclient/bin/Debug/websocket-sharp.dll.mdb and b/wsclient/bin/Debug/websocket-sharp.dll.mdb differ
diff --git a/wsclient/bin/Debug/wsclient.exe b/wsclient/bin/Debug/wsclient.exe
index 01d320cb..e5d37a65 100755
Binary files a/wsclient/bin/Debug/wsclient.exe and b/wsclient/bin/Debug/wsclient.exe differ
diff --git a/wsclient/bin/Debug/wsclient.exe.mdb b/wsclient/bin/Debug/wsclient.exe.mdb
index a4789812..15ee5a33 100644
Binary files a/wsclient/bin/Debug/wsclient.exe.mdb and b/wsclient/bin/Debug/wsclient.exe.mdb differ
diff --git a/wsclient/bin/Debug_Ubuntu/websocket-sharp.dll b/wsclient/bin/Debug_Ubuntu/websocket-sharp.dll
index 5a8e6cd9..8af4fa1f 100755
Binary files a/wsclient/bin/Debug_Ubuntu/websocket-sharp.dll and b/wsclient/bin/Debug_Ubuntu/websocket-sharp.dll differ
diff --git a/wsclient/bin/Debug_Ubuntu/websocket-sharp.dll.mdb b/wsclient/bin/Debug_Ubuntu/websocket-sharp.dll.mdb
index aa91a37d..5f51c80e 100644
Binary files a/wsclient/bin/Debug_Ubuntu/websocket-sharp.dll.mdb and b/wsclient/bin/Debug_Ubuntu/websocket-sharp.dll.mdb differ
diff --git a/wsclient/bin/Debug_Ubuntu/wsclient.exe b/wsclient/bin/Debug_Ubuntu/wsclient.exe
index d7ae3e72..cca0a0cc 100755
Binary files a/wsclient/bin/Debug_Ubuntu/wsclient.exe and b/wsclient/bin/Debug_Ubuntu/wsclient.exe differ
diff --git a/wsclient/bin/Debug_Ubuntu/wsclient.exe.mdb b/wsclient/bin/Debug_Ubuntu/wsclient.exe.mdb
index 3019a68a..047b062e 100644
Binary files a/wsclient/bin/Debug_Ubuntu/wsclient.exe.mdb and b/wsclient/bin/Debug_Ubuntu/wsclient.exe.mdb differ
diff --git a/wsclient/bin/Release/websocket-sharp.dll b/wsclient/bin/Release/websocket-sharp.dll
index 012e365b..022c9957 100755
Binary files a/wsclient/bin/Release/websocket-sharp.dll and b/wsclient/bin/Release/websocket-sharp.dll differ
diff --git a/wsclient/bin/Release/wsclient.exe b/wsclient/bin/Release/wsclient.exe
index cbffe9bc..881580e6 100755
Binary files a/wsclient/bin/Release/wsclient.exe and b/wsclient/bin/Release/wsclient.exe differ
diff --git a/wsclient/bin/Release_Ubuntu/websocket-sharp.dll b/wsclient/bin/Release_Ubuntu/websocket-sharp.dll
index 3844a3cd..fa19e1b4 100755
Binary files a/wsclient/bin/Release_Ubuntu/websocket-sharp.dll and b/wsclient/bin/Release_Ubuntu/websocket-sharp.dll differ
diff --git a/wsclient/bin/Release_Ubuntu/wsclient.exe b/wsclient/bin/Release_Ubuntu/wsclient.exe
index 3e36cff1..57263711 100755
Binary files a/wsclient/bin/Release_Ubuntu/wsclient.exe and b/wsclient/bin/Release_Ubuntu/wsclient.exe differ