Security Exception webservice

in my website http://ift.tt/1EvwneC i use web service .ashx for thumb images and it's work in local but in host no.

Security Exception

Description: The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file.

Exception Details: System.Security.SecurityException: System.Security.Permissions.SecurityPermission

var photo = ImageToByte(finalImage);
        var factory = (IWICComponentFactory)new WICImagingFactory();
        var inputStream = factory.CreateStream();
        inputStream.InitializeFromMemory(photo, (uint)photo.Length);
        var decoder = factory.CreateDecoderFromStream(inputStream, null, WICDecodeOptions.WICDecodeMetadataCacheOnLoad);
        var frame = decoder.GetFrame(0);
        // Compute target size
        uint thumbWidth, thumbHeight;
        thumbWidth =Convert.ToUInt32( photowidth);
        thumbHeight = Convert.ToUInt32(photoheight) ;
        // Prepare output stream to cache file
        var outputStream = new MemoryIStream();
        // Prepare JPG encoder
        var encoder = factory.CreateEncoder(Consts.GUID_ContainerFormatJpeg, null);
        encoder.Initialize(outputStream, WICBitmapEncoderCacheOption.WICBitmapEncoderNoCache);
        // Prepare output frame
        IWICBitmapFrameEncode outputFrame;
        var arg = new IPropertyBag2[1];
        encoder.CreateNewFrame(out outputFrame, arg);
        var propBag = arg[0];
        var propertyBagOption = new PROPBAG2[1];
        propertyBagOption[0].pstrName = "ImageQuality";
        propBag.Write(1, propertyBagOption, new object[] { 0.85F });
        outputFrame.Initialize(propBag);
        outputFrame.SetResolution(96, 96);
        outputFrame.SetSize(thumbWidth, thumbHeight);
        // Prepare scaler
        var scaler = factory.CreateBitmapScaler();
        scaler.Initialize(frame, thumbWidth, thumbHeight, WICBitmapInterpolationMode.WICBitmapInterpolationModeFant);
        // Write the scaled source to the output frame
        outputFrame.WriteSource(scaler, new WICRect { X = 0, Y = 0, Width = (int)thumbWidth, Height = (int)thumbHeight });
        outputFrame.Commit();
        encoder.Commit();
        var outputArray = outputStream.ToArray();
        outputStream.Close();

        var cachePolicy = context.Response.Cache;
        cachePolicy.SetCacheability(HttpCacheability.Public);
        cachePolicy.SetOmitVaryStar(true);
        cachePolicy.SetExpires(DateTime.Now + TimeSpan.FromDays(365));
        cachePolicy.SetValidUntilExpires(true);
        cachePolicy.SetLastModified(File.GetLastWriteTime(photoPath));
        // Write to the cache file
        //File.WriteAllBytes(photoCachePath, outputArray);
        // Write to the response
        context.Response.ContentType = "image/jpg";
        context.Response.OutputStream.Write(outputArray, 0, outputArray.Length);

show error for this

var factory = (IWICComponentFactory)new WICImagingFactory();