diff --git a/pokerth_lib.pro b/pokerth_lib.pro
index 1341264e..ce9604bd 100644
--- a/pokerth_lib.pro
+++ b/pokerth_lib.pro
@@ -242,4 +242,5 @@ mac{
     INCLUDEPATH += /Developer/SDKs/MacOSX10.5.sdk/usr/include/
 	INCLUDEPATH += /Library/Frameworks/SDL.framework/Headers
 	INCLUDEPATH += /Library/Frameworks/SDL_mixer.framework/Headers
+	INCLUDEPATH += /opt/local/include
 }
diff --git a/src/net/clientstate.h b/src/net/clientstate.h
index 74d3da6b..faa67f94 100644
--- a/src/net/clientstate.h
+++ b/src/net/clientstate.h
@@ -266,6 +266,42 @@ protected:
 	virtual void InternalHandlePacket(boost::shared_ptr<ClientThread> client, boost::shared_ptr<NetPacket> tmpPacket) = 0;
 };
 
+// State: Wait for Authentication Challenge.
+class ClientStateWaitAuthChallenge : public AbstractClientStateReceiving
+{
+public:
+	// Access the state singleton.
+	static ClientStateWaitAuthChallenge &Instance();
+	virtual ~ClientStateWaitAuthChallenge();
+
+	virtual void Enter(boost::shared_ptr<ClientThread> client);
+	virtual void Exit(boost::shared_ptr<ClientThread> client);
+
+protected:
+	// Protected constructor - this is a singleton.
+	ClientStateWaitAuthChallenge();
+
+	virtual void InternalHandlePacket(boost::shared_ptr<ClientThread> client, boost::shared_ptr<NetPacket> tmpPacket);
+};
+
+// State: Wait for Authentication Verification.
+class ClientStateWaitAuthVerify : public AbstractClientStateReceiving
+{
+public:
+	// Access the state singleton.
+	static ClientStateWaitAuthVerify &Instance();
+	virtual ~ClientStateWaitAuthVerify();
+
+	virtual void Enter(boost::shared_ptr<ClientThread> client);
+	virtual void Exit(boost::shared_ptr<ClientThread> client);
+
+protected:
+	// Protected constructor - this is a singleton.
+	ClientStateWaitAuthVerify();
+
+	virtual void InternalHandlePacket(boost::shared_ptr<ClientThread> client, boost::shared_ptr<NetPacket> tmpPacket);
+};
+
 // State: Wait for Session ACK.
 class ClientStateWaitSession : public AbstractClientStateReceiving
 {
diff --git a/src/net/clientthread.h b/src/net/clientthread.h
index 904d32ed..7a4a61a5 100644
--- a/src/net/clientthread.h
+++ b/src/net/clientthread.h
@@ -267,6 +267,8 @@ friend class ClientStateWaitChooseServer;
 friend class ClientStateStartConnect;
 friend class ClientStateConnecting;
 friend class ClientStateStartSession;
+friend class ClientStateWaitAuthChallenge;
+friend class ClientStateWaitAuthVerify;
 friend class ClientStateWaitSession;
 friend class ClientStateWaitJoin;
 friend class ClientStateWaitGame;
diff --git a/src/net/common/clientstate.cpp b/src/net/common/clientstate.cpp
index b0b7fc6b..a61aaa41 100644
--- a/src/net/common/clientstate.cpp
+++ b/src/net/common/clientstate.cpp
@@ -676,10 +676,11 @@ ClientStateStartSession::Enter(boost::shared_ptr<ClientThread> client)
 	netInit->requestedVersion.minor = NET_VERSION_MINOR;
 	netInit->login.present = login_PR_authenticatedLogin;
 	AuthenticatedLogin_t *authLogin = &netInit->login.choice.authenticatedLogin;
-	// TODO
+	// Send authentication user data for challenge/response in init.
 	boost::shared_ptr<SessionData> tmpSession = context.GetSessionData();
 	tmpSession->CreateClientAuthSession(client->GetAuthContext(), context.GetPlayerName(), context.GetPassword());
-	tmpSession->AuthStep(1, "");
+	if (!tmpSession->AuthStep(1, ""))
+		throw ClientException(__FILE__, __LINE__, ERR_NET_INVALID_PASSWORD, 0);
 	string outUserData(tmpSession->AuthGetNextOutMsg());
 	OCTET_STRING_fromBuf(&authLogin->clientUserData,
 						 outUserData.c_str(),
@@ -700,7 +701,7 @@ ClientStateStartSession::Enter(boost::shared_ptr<ClientThread> client)
 	}
 	client->GetSender().Send(context.GetSessionData(), init);
 
-	client->SetState(ClientStateWaitSession::Instance());
+	client->SetState(ClientStateWaitAuthChallenge::Instance());
 }
 
 void
@@ -1008,6 +1009,118 @@ AbstractClientStateReceiving::HandlePacket(boost::shared_ptr<ClientThread> clien
 
 //-----------------------------------------------------------------------------
 
+ClientStateWaitAuthChallenge &
+ClientStateWaitAuthChallenge::Instance()
+{
+	static ClientStateWaitAuthChallenge state;
+	return state;
+}
+
+ClientStateWaitAuthChallenge::ClientStateWaitAuthChallenge()
+{
+}
+
+ClientStateWaitAuthChallenge::~ClientStateWaitAuthChallenge()
+{
+}
+
+void
+ClientStateWaitAuthChallenge::Enter(boost::shared_ptr<ClientThread> client)
+{
+	// Now we finally start receiving data.
+	client->StartAsyncRead();
+}
+
+void
+ClientStateWaitAuthChallenge::Exit(boost::shared_ptr<ClientThread> /*client*/)
+{
+}
+
+void
+ClientStateWaitAuthChallenge::InternalHandlePacket(boost::shared_ptr<ClientThread> client, boost::shared_ptr<NetPacket> tmpPacket)
+{
+	if (tmpPacket->GetMsg()->present == PokerTHMessage_PR_authMessage)
+	{
+		// Check subtype.
+		AuthMessage_t *netAuth = &tmpPacket->GetMsg()->choice.authMessage;
+		if (netAuth->present == AuthMessage_PR_authServerChallenge)
+		{
+			AuthServerChallenge_t *netChallenge = &netAuth->choice.authServerChallenge;
+			string challengeStr((const char *)netChallenge->serverChallenge.buf, netChallenge->serverChallenge.size);
+			boost::shared_ptr<SessionData> tmpSession = client->GetContext().GetSessionData();
+			if (!tmpSession->AuthStep(2, challengeStr.c_str()))
+				throw ClientException(__FILE__, __LINE__, ERR_NET_INVALID_PASSWORD, 0);
+			string outUserData(tmpSession->AuthGetNextOutMsg());
+
+
+			boost::shared_ptr<NetPacket> packet(new NetPacket(NetPacket::Alloc));
+			packet->GetMsg()->present = PokerTHMessage_PR_authMessage;
+			AuthMessage_t *outAuth = &packet->GetMsg()->choice.authMessage;
+			outAuth->present = AuthMessage_PR_authClientResponse;
+			AuthClientResponse_t *outResponse = &outAuth->choice.authClientResponse;
+
+			OCTET_STRING_fromBuf(&outResponse->clientResponse,
+								 outUserData.c_str(),
+								 outUserData.length());
+			client->GetSender().Send(tmpSession, packet);
+			client->SetState(ClientStateWaitAuthVerify::Instance());
+		}
+		else
+			throw ClientException(__FILE__, __LINE__, ERR_NET_INVALID_PASSWORD, 0);
+	}
+}
+
+//-----------------------------------------------------------------------------
+
+ClientStateWaitAuthVerify &
+ClientStateWaitAuthVerify::Instance()
+{
+	static ClientStateWaitAuthVerify state;
+	return state;
+}
+
+ClientStateWaitAuthVerify::ClientStateWaitAuthVerify()
+{
+}
+
+ClientStateWaitAuthVerify::~ClientStateWaitAuthVerify()
+{
+}
+
+void
+ClientStateWaitAuthVerify::Enter(boost::shared_ptr<ClientThread> /*client*/)
+{
+}
+
+void
+ClientStateWaitAuthVerify::Exit(boost::shared_ptr<ClientThread> /*client*/)
+{
+}
+
+void
+ClientStateWaitAuthVerify::InternalHandlePacket(boost::shared_ptr<ClientThread> client, boost::shared_ptr<NetPacket> tmpPacket)
+{
+	if (tmpPacket->GetMsg()->present == PokerTHMessage_PR_authMessage)
+	{
+		// Check subtype.
+		AuthMessage_t *netAuth = &tmpPacket->GetMsg()->choice.authMessage;
+		if (netAuth->present == AuthMessage_PR_authServerVerification)
+		{
+			AuthServerVerification_t *netVerification = &netAuth->choice.authServerVerification;
+			string verificationStr((const char *)netVerification->serverVerification.buf, netVerification->serverVerification.size);
+			boost::shared_ptr<SessionData> tmpSession = client->GetContext().GetSessionData();
+			if (!tmpSession->AuthStep(3, verificationStr.c_str()))
+				throw ClientException(__FILE__, __LINE__, ERR_NET_INVALID_PASSWORD, 0);
+
+			client->SetState(ClientStateWaitSession::Instance());
+		}
+		else
+			throw ClientException(__FILE__, __LINE__, ERR_NET_INVALID_PASSWORD, 0);
+	}
+}
+
+//-----------------------------------------------------------------------------
+
 ClientStateWaitSession &
 ClientStateWaitSession::Instance()
 {
@@ -1024,10 +1137,8 @@ ClientStateWaitSession::~ClientStateWaitSession()
 }
 
 void
-ClientStateWaitSession::Enter(boost::shared_ptr<ClientThread> client)
+ClientStateWaitSession::Enter(boost::shared_ptr<ClientThread> /*client*/)
 {
-	// Now we finally start receiving data.
-	client->StartAsyncRead();
 }
 
 void