// Authenticate is the core method for this custom authentication.
// When an Internet resource requests authentication, the WebRequest.GetResponse 
// method calls the AuthenticationManager.Authenticate method. This method, in 
// turn, calls the Authenticate method on each of the registered authentication
// modules, in the order in which they were registered. When the authentication is 
// complete an Authorization object is returned to the WebRequest.
public Authorization Authenticate(String challenge, WebRequest request, ICredentials credentials) 
{
  Encoding ASCII = Encoding.ASCII;        

  // Get the username and password from the credentials
  NetworkCredential MyCreds = credentials.GetCredential(request.RequestUri, "Basic");        

  if (PreAuthenticate(request, credentials) == null)
    Console.WriteLine("\n Pre-authentication is not allowed.");
  else
    Console.WriteLine("\n Pre-authentication is allowed.");

  // Verify that the challenge satisfies the authorization requirements.
  bool challengeOk = checkChallenge(challenge, MyCreds.Domain);

  if (!challengeOk)
    return null;

  // Create the encrypted string according to the Basic authentication format as
  // follows:
  // a)Concatenate the username and password separated by colon;
  // b)Apply ASCII encoding to obtain a stream of bytes;
  // c)Apply Base64 encoding to this array of bytes to obtain the encoded 
  // authorization.
  string BasicEncrypt = MyCreds.UserName + ":" + MyCreds.Password;

  string BasicToken = "Basic " + Convert.ToBase64String(ASCII.GetBytes(BasicEncrypt));

  // Create an Authorization object using the encoded authorization above.
  Authorization resourceAuthorization = new Authorization(BasicToken);

  // Get the Message property, which contains the authorization string that the 
  // client returns to the server when accessing protected resources.
  Console.WriteLine("\n Authorization Message:{0}",resourceAuthorization.Message);

  // Get the Complete property, which is set to true when the authentication process 
  // between the client and the server is finished.
  Console.WriteLine("\n Authorization Complete:{0}",resourceAuthorization.Complete);

  Console.WriteLine("\n Authorization ConnectionGroupId:{0}",resourceAuthorization.ConnectionGroupId);

  return resourceAuthorization;
}

public Authorization Authenticate( string challenge,WebRequest request,ICredentials credentials)
{
    try
    {
        string message;
        // Check if Challenge string was raised by a site which requires 'CloneBasic' authentication.
        if ((challenge == null) || (!challenge.StartsWith("CloneBasic")))
            return null; 
        NetworkCredential myCredentials;
        if (credentials is CredentialCache)
        {
            myCredentials = credentials.GetCredential(request.RequestUri,"CloneBasic");
            if (myCredentials == null)
                return null;
        }
        else
        {
            myCredentials = (NetworkCredential)credentials;
        }
        // Message encryption scheme : 
        //   a)Concatenate username and password seperated by space;
        //   b)Apply ASCII encoding to obtain a stream of bytes;
        //   c)Apply Base64 Encoding to this array of bytes to obtain our encoded authorization message.

        message = myCredentials.UserName + " " + myCredentials.Password;
        // Apply AsciiEncoding to 'message' string to obtain it as an array of bytes.
        Encoding ascii = Encoding.ASCII;
        byte[] byteArray = new byte[ascii.GetByteCount(message)];
        byteArray = ascii.GetBytes(message);

        // Performing Base64 transformation.
        message = Convert.ToBase64String(byteArray);
        Authorization myAuthorization = new Authorization("CloneBasic " + message,true);
        string[] protectionRealm = new string[]{request.RequestUri.AbsolutePath};
        myAuthorization.ProtectionRealm = protectionRealm;

        return myAuthorization;
    }
    catch(Exception e)
    {
        Console.WriteLine("The following exception was raised in Authenticate method:{0}",e.Message);
        return null;
    }
  }

public Authorization Authenticate( string challenge,WebRequest request,ICredentials credentials)
{
    try
    {
        string message;
        // Check if Challenge string was raised by a site which requires CloneBasic authentication.
        if ((challenge == null) || (!challenge.StartsWith("CloneBasic")))
            return null; 
        NetworkCredential myCredentials;
        if (credentials is CredentialCache)
        {
            myCredentials = credentials.GetCredential(request.RequestUri,"CloneBasic");
            if (myCredentials == null)
                return null;
        }
        else
        {
            myCredentials = (NetworkCredential)credentials;
        }
        // Message encryption scheme : 
        // a)Concatenate username and password seperated by space;
        // b)Apply ASCII encoding to obtain a stream of bytes;
        // c)Apply Base64 Encoding to this array of bytes to obtain our encoded authorization message.

        message = myCredentials.UserName + " " + myCredentials.Password;
        // Apply AsciiEncoding to our user name and password to obtain it as an array of bytes.
        Encoding asciiEncoding = Encoding.ASCII;
        byte[] byteArray = new byte[asciiEncoding.GetByteCount(message)];
        byteArray = asciiEncoding.GetBytes(message);

        // Perform Base64 transform.
        message = Convert.ToBase64String(byteArray);
    // The following overloaded contructor sets the 'Message' property of authorization to the base64 string;
    // that  we just formed and it also sets the 'Complete' property to true and the connection group id;
    // to the domain of the NetworkCredential object.
        Authorization myAuthorization = new Authorization("CloneBasic " + message,true,request.ConnectionGroupName);
        return myAuthorization;
    }
    catch(Exception e)
    {
            Console.WriteLine("Exception Raised ...:"+e.Message);    
        return null;
    }
  }