diff --git a/dotnet/IEC61850forCSharp/AcseAuthenticationParameter.cs b/dotnet/IEC61850forCSharp/AcseAuthenticationParameter.cs
new file mode 100644
index 00000000..1e5496b6
--- /dev/null
+++ b/dotnet/IEC61850forCSharp/AcseAuthenticationParameter.cs
@@ -0,0 +1,101 @@
+/*
+ *  AcseAuthenticationParameter.cs
+ *
+ *  Copyright 2014 Michael Zillgith
+ *
+ *  This file is part of libIEC61850.
+ *
+ *  libIEC61850 is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  libIEC61850 is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with libIEC61850.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *  See COPYING file for the complete license text.
+ */
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Text;
+
+// IEC 61850 API for the libiec61850 .NET wrapper library
+namespace IEC61850
+{
+    /// <summary>
+    /// Authentication mechanism used by AcseAuthenticator
+    /// </summary>
+    public enum AcseAuthenticationMechanism
+    {
+        /** Neither ACSE nor TLS authentication used */
+        ACSE_AUTH_NONE = 0,
+
+        /** Use ACSE password for client authentication */
+        ACSE_AUTH_PASSWORD = 1,
+
+        /** Use ACSE certificate for client authentication */
+        ACSE_AUTH_CERTIFICATE = 2,
+
+        /** Use TLS certificate for client authentication */
+        ACSE_AUTH_TLS = 3
+    }
+    
+
+    public class AcseAuthenticationParameter
+    {
+        [DllImport("iec61850", CallingConvention = CallingConvention.Cdecl)]
+        static extern IntPtr AcseAuthenticationParameter_create();
+
+        [DllImport("iec61850", CallingConvention = CallingConvention.Cdecl)]
+        static extern void AcseAuthenticationParameter_setAuthMechanism(IntPtr self, int mechanism);
+        
+        [DllImport("iec61850", CallingConvention = CallingConvention.Cdecl)]
+        static extern void AcseAuthenticationParameter_setPassword(IntPtr self, string password);
+        
+        [DllImport("iec61850", CallingConvention = CallingConvention.Cdecl)]
+        static extern int AcseAuthenticationParameter_getAuthMechanism(IntPtr self);
+
+        private IntPtr self = IntPtr.Zero;
+
+        public AcseAuthenticationParameter()
+        {
+            self = AcseAuthenticationParameter_create();
+        }
+
+        public AcseAuthenticationParameter(IntPtr self)
+        {
+            this.self = self;  
+        }
+
+        public void SetAuthMechanism(AcseAuthenticationMechanism acseAuthenticationMechanism)
+        {
+            AcseAuthenticationParameter_setAuthMechanism(self,(int)acseAuthenticationMechanism);
+        }
+
+        public void SetPassword(string password)
+        {
+            AcseAuthenticationParameter_setPassword(self, password);
+        }
+
+        public AcseAuthenticationMechanism GetAuthMechanism()
+        {
+            return (AcseAuthenticationMechanism)AcseAuthenticationParameter_getAuthMechanism(self);
+        }
+    }
+
+    public class IsoApplicationReference
+    {
+        private IntPtr self = IntPtr.Zero;
+
+        public IsoApplicationReference(IntPtr self)
+        {
+            this.self= self;
+        }
+    }
+}
diff --git a/dotnet/IEC61850forCSharp/IEC61850ServerAPI.cs b/dotnet/IEC61850forCSharp/IEC61850ServerAPI.cs
index 8f321fce..27cf390d 100644
--- a/dotnet/IEC61850forCSharp/IEC61850ServerAPI.cs
+++ b/dotnet/IEC61850forCSharp/IEC61850ServerAPI.cs
@@ -25,7 +25,10 @@ using IEC61850.Model;
 using IEC61850.TLS;
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Data.Common;
 using System.Runtime.InteropServices;
+using System.Security.Principal;
 
 // IEC 61850 API for the libiec61850 .NET wrapper library
 namespace IEC61850
@@ -1749,6 +1752,9 @@ namespace IEC61850
 
         public class ClientConnection : IDisposable
         {
+            [DllImport("iec61850", CallingConvention = CallingConvention.Cdecl)]
+            static extern IntPtr ClientConnection_getSecurityToken(IntPtr self);
+
             [DllImport("iec61850", CallingConvention = CallingConvention.Cdecl)]
             static extern IntPtr ClientConnection_getPeerAddress(IntPtr self);
 
@@ -1772,6 +1778,31 @@ namespace IEC61850
                 this.self = ClientConnection_claimOwnership(self);
             }
 
+            /// <summary>
+            /// Get the security token associated with this connection
+            /// The security token is an opaque handle that is associated with the connection.It is provided by the
+            /// authenticator (if one is present). If no security token is used then this function returns NULL
+            /// </summary>
+            /// <returns>the security token or NULL</returns>
+            public object GetSecurityToken()
+            {
+                lock (this)
+                {
+                    if (self != IntPtr.Zero)
+                    {
+                        IntPtr token = ClientConnection_getSecurityToken(self);
+
+                        if (token != IntPtr.Zero)
+                        {
+                            GCHandle handle = GCHandle.FromIntPtr(token);
+                            return handle as object;
+                        }
+                    }
+                }
+
+                return null;
+            }
+
             public string GetPeerAddress()
             {
                 lock (this)
@@ -2611,6 +2642,29 @@ namespace IEC61850
             [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
             private delegate void IedServer_SVCBEventHandler(IntPtr svcb, int eventType, IntPtr parameter);
 
+            /// <summary>
+            /// set the authenticator for this server
+            /// This function sets a user specified authenticator that is used to identify and authenticate clients that
+            /// wants to connect.The authenticator is called on each connection attempt.Depending on the return value
+            /// connections are accepted.
+            /// </summary>
+            /// <param name="self">the instance of IedServer to operate on.</param>
+            /// <param name="authenticator">the user provided authenticator callback</param>
+            /// <param name="authenticatorParameter">user provided parameter that is passed to the authenticator</param>
+            [DllImport("iec61850", CallingConvention = CallingConvention.Cdecl)]
+            static extern void IedServer_setAuthenticator(IntPtr self, IedServer_AcseAuthenticator authenticator, IntPtr authenticatorParameter);
+
+            /// <summary>
+            /// Callback function to authenticate a client
+            /// </summary>
+            /// <param name="parameter">user provided parameter - set when user registers the authenticator</param>
+            /// <param name="authParameter">the authentication parameters provided by the client</param>
+            /// <param name="securityToken">pointer where to store an application specific security token - can be ignored if not used.</param>
+            /// <param name="appReference">ISO application reference (ap-title + ae-qualifier)</param>
+            /// <returns>true if client connection is accepted, false otherwise</returns>
+            [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+            private delegate bool IedServer_AcseAuthenticator(IntPtr parameter, IntPtr authParameter, IntPtr securityToken, IntPtr appReference);
+
             /// <summary>
             /// callback handler to control client read access to data attributes
             ///  User provided callback function to control MMS client read access to IEC 61850
@@ -3166,7 +3220,6 @@ namespace IEC61850
                 IedServer_setSVCBHandler(self, sampledValuesControlBlock.Self, internalSVCBEventHandler, GCHandle.ToIntPtr(info.handle));
             }
 
-
             private void InternalSVCBEventHandlerImplementation(IntPtr svcb, int eventType, IntPtr parameter)
             {
                 GCHandle handle = GCHandle.FromIntPtr(parameter);
@@ -3177,6 +3230,38 @@ namespace IEC61850
                     info.sVCBEventHandler(info.sampledValuesControlBlock, (SMVEvent)eventType, info.svcHandlerParameter);
             }
 
+            //TODO -> Add appReference
+            public delegate bool AcseAuthenticatorHandler(object parameter, AcseAuthenticationParameter authParameter, object securityToken, IsoApplicationReference isoApplicationReference);
+
+            private AcseAuthenticatorHandler acseAuthenticatorHandler = null;
+            private object acseAuthenticatorHandlerParameter = null;
+            private IedServer_AcseAuthenticator iedServer_AcseAuthenticator = null;
+
+            public void SetAuthenticator(AcseAuthenticatorHandler acseAuthenticatorHandler, object acseAuthenticatorHandlerParameter)
+            {
+                this.acseAuthenticatorHandler = acseAuthenticatorHandler;
+                this.acseAuthenticatorHandlerParameter= acseAuthenticatorHandlerParameter;
+
+                if(iedServer_AcseAuthenticator == null)
+                {
+                    iedServer_AcseAuthenticator = new IedServer_AcseAuthenticator(InternalAcseAuthenticator);
+                    IedServer_setAuthenticator(self, iedServer_AcseAuthenticator, IntPtr.Zero);
+                }
+            }
+
+            private bool InternalAcseAuthenticator(IntPtr parameter, IntPtr authParameter, IntPtr securityToken, IntPtr appReference)
+            {
+                if(acseAuthenticatorHandler != null && authParameter != IntPtr.Zero && appReference != IntPtr.Zero)
+                {
+                    AcseAuthenticationParameter acseAuthenticationParameter = new AcseAuthenticationParameter(authParameter);
+                    IsoApplicationReference isoApplicationReference = new IsoApplicationReference(appReference);
+                    GCHandle token = GCHandle.FromIntPtr(securityToken);
+                    return acseAuthenticatorHandler(acseAuthenticatorHandlerParameter, acseAuthenticationParameter, token as object, isoApplicationReference);
+                }
+
+                return false;
+            }
+
             public delegate MmsDataAccessError ReadAccessHandler(LogicalDevice ld, LogicalNode ln, DataObject dataObject, FunctionalConstraint fc, ClientConnection connection, object parameter);
 
             private ReadAccessHandler readAccessHandler = null;
diff --git a/dotnet/server_example_access_control/Program.cs b/dotnet/server_example_access_control/Program.cs
index 2e6784e1..ac67dbef 100644
--- a/dotnet/server_example_access_control/Program.cs
+++ b/dotnet/server_example_access_control/Program.cs
@@ -17,6 +17,7 @@ using IEC61850.Client;
 using ReportControlBlock = IEC61850.Server.ReportControlBlock;
 using IEC61850.Model;
 using System.Data.Common;
+using IEC61850;
 
 namespace server_access_control
 {
@@ -142,12 +143,23 @@ namespace server_access_control
             /* Install handler to control access to control blocks (RCBs, LCBs, GoCBs, SVCBs, SGCBs)*/
             bool ControlBlockAccessCallBack(object parameter, ClientConnection connection, ACSIClass acsiClass, LogicalDevice ld, LogicalNode ln, string objectName, string subObjectName, ControlBlockAccessType accessType)
             {
+                string password = parameter as string;
+                object securityToken = connection.GetSecurityToken();
+
+                if(securityToken != null)
+                {
+                    if ((securityToken as string == password))
+                        Console.WriteLine("Correct securityToken");
+                    else
+                        Console.WriteLine("Incorrect securityToken");
+                }
+
                 Console.WriteLine(acsiClass.ToString() + " "+ accessType.ToString() + " access " +  ld.GetName() + ln.GetName() +"/"+ objectName + "." + subObjectName + "\n");
 
                 return true;
             }
 
-            iedServer.SetControlBlockAccessHandler(ControlBlockAccessCallBack, iedServer);
+            iedServer.SetControlBlockAccessHandler(ControlBlockAccessCallBack, "securityToken_password");
 
             /* By default access to variables with FC=DC and FC=CF is not allowed.
             * This allow to write to simpleIOGenericIO/GGIO1.NamPlt.vendor variable used
@@ -332,6 +344,22 @@ namespace server_access_control
             iedServer.SetSVCBHandler(sVCBEventHandler, sampledValuesControlBlock_1, null);
             iedServer.SetSVCBHandler(sVCBEventHandler, sampledValuesControlBlock_2, null);
 
+            
+            bool clientAuthenticator (object parameter, AcseAuthenticationParameter authParameter, object securityToken, IsoApplicationReference isoApplicationReference)
+            {
+                Console.WriteLine("ACSE Authenticator:\n");
+
+                IEC61850.AcseAuthenticationMechanism acseAuthenticationMechanism = authParameter.GetAuthMechanism();
+
+                if (acseAuthenticationMechanism == IEC61850.AcseAuthenticationMechanism.ACSE_AUTH_PASSWORD)
+                {
+
+                }
+                return false;
+            }
+
+            iedServer.SetAuthenticator(clientAuthenticator, null);
+
             iedServer.Start(102);
 
             if (iedServer.IsRunning())
diff --git a/examples/iec61850_client_example5/client_example5.c b/examples/iec61850_client_example5/client_example5.c
index e5bb22b7..973057a7 100644
--- a/examples/iec61850_client_example5/client_example5.c
+++ b/examples/iec61850_client_example5/client_example5.c
@@ -84,6 +84,8 @@ main(int argc, char** argv)
         printf("Failed to connect to %s:%i\n", hostname, tcpPort);
     }
 
+    while (true);
+
     IedConnection_destroy(con);
 
     AcseAuthenticationParameter_destroy(auth);
diff --git a/src/mms/inc/iso_connection_parameters.h b/src/mms/inc/iso_connection_parameters.h
index cc443daf..af5a3db0 100644
--- a/src/mms/inc/iso_connection_parameters.h
+++ b/src/mms/inc/iso_connection_parameters.h
@@ -91,6 +91,9 @@ AcseAuthenticationParameter_destroy(AcseAuthenticationParameter self);
 LIB61850_API void
 AcseAuthenticationParameter_setAuthMechanism(AcseAuthenticationParameter self, AcseAuthenticationMechanism mechanism);
 
+LIB61850_API AcseAuthenticationMechanism
+AcseAuthenticationParameter_getAuthMechanism(AcseAuthenticationParameter self);
+
 LIB61850_API void
 AcseAuthenticationParameter_setPassword(AcseAuthenticationParameter self, char* password);
 
diff --git a/src/mms/iso_common/iso_connection_parameters.c b/src/mms/iso_common/iso_connection_parameters.c
index 858def8d..2478db6e 100644
--- a/src/mms/iso_common/iso_connection_parameters.c
+++ b/src/mms/iso_common/iso_connection_parameters.c
@@ -63,6 +63,12 @@ AcseAuthenticationParameter_setAuthMechanism(AcseAuthenticationParameter self, A
     self->mechanism = mechanism;
 }
 
+AcseAuthenticationMechanism
+AcseAuthenticationParameter_getAuthMechanism(AcseAuthenticationParameter self)
+{
+    return self->mechanism;
+}
+
 IsoConnectionParameters
 IsoConnectionParameters_create()
 {