diff --git a/System.Application.SteamTools.Client.Desktop.Avalonia.App/Program.cs b/System.Application.SteamTools.Client.Desktop.Avalonia.App/Program.cs
index 5edf0161d..2ca64db37 100644
--- a/System.Application.SteamTools.Client.Desktop.Avalonia.App/Program.cs
+++ b/System.Application.SteamTools.Client.Desktop.Avalonia.App/Program.cs
@@ -5,7 +5,7 @@ using System.IO;
 using System.Properties;
 using System.Reflection;
 using System.Threading.Tasks;
-using System.Windows;
+using LogLevel = Microsoft.Extensions.Logging.LogLevel;
 
 [assembly: AssemblyTitle(ThisAssembly.AssemblyTrademark + " v" + ThisAssembly.Version)]
 namespace System.Application.UI
@@ -36,7 +36,7 @@ namespace System.Application.UI
             }
             catch (Exception ex)
             {
-                AppHelper.SetNLoggerMinLevel(LogLevel.Trace);
+                AppHelper.TrySetLoggerMinLevel(LogLevel.Trace);
                 // NLog: catch any exception and log it.
                 logger.Error(ex, "Stopped program because of exception");
 #if DEBUG
diff --git a/System.Application.SteamTools.Client.Desktop/UI/AppHelper.cs b/System.Application.SteamTools.Client.Desktop/UI/AppHelper.cs
index 96555e9fc..c72b1b2cb 100644
--- a/System.Application.SteamTools.Client.Desktop/UI/AppHelper.cs
+++ b/System.Application.SteamTools.Client.Desktop/UI/AppHelper.cs
@@ -65,12 +65,24 @@ namespace System.Application.UI
 
         static void SetNLoggerMinLevel(LogLevel logLevel) => SetNLoggerMinLevel(ConvertLogLevel(logLevel));
 
-        public static void SetNLoggerMinLevel(NLogLevel logLevel)
+        static void SetNLoggerMinLevel(NLogLevel logLevel)
         {
             NLogManager.GlobalThreshold = logLevel;
             NInternalLogger.LogLevel = logLevel;
         }
 
+        public static void TrySetLoggerMinLevel(LogLevel logLevel)
+        {
+            try
+            {
+                LoggerFilterOptions.MinLevel = logLevel;
+            }
+            catch
+            {
+            }
+            SetNLoggerMinLevel(ConvertLogLevel(logLevel));
+        }
+
         /// <summary>
         /// 日志过滤选项
         /// </summary>
diff --git a/System.Application.SteamTools.Client/Models/AppSettings.cs b/System.Application.SteamTools.Client/Models/AppSettings.cs
index 5fa246ce8..753a352fc 100644
--- a/System.Application.SteamTools.Client/Models/AppSettings.cs
+++ b/System.Application.SteamTools.Client/Models/AppSettings.cs
@@ -52,5 +52,28 @@ namespace System.Application.Models
         [N_JsonProperty("3")]
         [S_JsonProperty("3")]
         public string? AppSecretVisualStudioAppCenter { get; set; }
+
+        [MPKey(4)]
+        [N_JsonProperty("4")]
+        [S_JsonProperty("4")]
+        public string? RSASecret { get; set; }
+
+        RSA? rsa;
+
+        [MPIgnore]
+        [N_JsonIgnore]
+        [S_JsonIgnore]
+        public RSA RSA
+        {
+            get
+            {
+                if (rsa == null)
+                {
+                    if (RSASecret == null) throw new ArgumentNullException(nameof(RSASecret));
+                    rsa = RSAUtils.CreateFromJsonString(RSASecret);
+                }
+                return rsa;
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/System.Application.SteamTools.Services.CloudService.Models/Models/ApiResponseCode.cs b/System.Application.SteamTools.Services.CloudService.Models/Models/ApiResponseCode.cs
index af06649f0..ac6407044 100644
--- a/System.Application.SteamTools.Services.CloudService.Models/Models/ApiResponseCode.cs
+++ b/System.Application.SteamTools.Services.CloudService.Models/Models/ApiResponseCode.cs
@@ -105,6 +105,8 @@ namespace System.Application.Models
 
         EmptyUserAgent,
 
+        RequiredSecurityKey,
+
         #endregion
     }
 }
\ No newline at end of file
diff --git a/System.Application.SteamTools.Services.CloudService.Models/Services.CloudService/Constants.cs b/System.Application.SteamTools.Services.CloudService.Models/Services.CloudService/Constants.cs
index 6ebf0c756..6fbf66457 100644
--- a/System.Application.SteamTools.Services.CloudService.Models/Services.CloudService/Constants.cs
+++ b/System.Application.SteamTools.Services.CloudService.Models/Services.CloudService/Constants.cs
@@ -10,8 +10,21 @@ namespace System.Application.Services.CloudService
 
         public static string NetworkConnectionInterruption => SR.NetworkConnectionInterruption;
 
+        public static class Headers
+        {
+            public static class Request
+            {
+                public const string AppVersion = "App-Version";
+                public const string SecurityKey = "App-SKey";
+            }
+        }
+
         public const string HeaderAppVersion = "App-Version";
 
+        public const string HeaderSecurityKey = "App-S-Key";
+
+        public const string HeaderRspCiphertext = "App-Rsp-Ciphertext";
+
         /// <summary>
         /// 短信间隔，60秒
         /// </summary>
diff --git a/System.Application.SteamTools.Services.CloudService/HttpContentCompat.cs b/System.Application.SteamTools.Services.CloudService/HttpContentCompat.cs
new file mode 100644
index 000000000..051ba2a1f
--- /dev/null
+++ b/System.Application.SteamTools.Services.CloudService/HttpContentCompat.cs
@@ -0,0 +1,29 @@
+#if !NET5_0_OR_GREATER
+using System.IO;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+// ReSharper disable once CheckNamespace
+namespace System
+{
+    public static class HttpContentCompat
+    {
+        public static Task<byte[]> ReadAsByteArrayAsync(this HttpContent @this, CancellationToken _)
+        {
+            return @this.ReadAsByteArrayAsync();
+        }
+
+        public static Task<Stream> ReadAsStreamAsync(this HttpContent @this, CancellationToken _)
+        {
+            return @this.ReadAsStreamAsync();
+        }
+
+        public static Task<string> ReadAsStringAsync(this HttpContent @this, CancellationToken _)
+        {
+            return @this.ReadAsStringAsync();
+        }
+    }
+}
+
+#endif
\ No newline at end of file
diff --git a/System.Application.SteamTools.Services.CloudService/Models/ICloudServiceSettings.cs b/System.Application.SteamTools.Services.CloudService/Models/ICloudServiceSettings.cs
index 9d4272f41..dd2a51073 100644
--- a/System.Application.SteamTools.Services.CloudService/Models/ICloudServiceSettings.cs
+++ b/System.Application.SteamTools.Services.CloudService/Models/ICloudServiceSettings.cs
@@ -1,4 +1,4 @@
-using System.Application.Services.CloudService;
+using System.Security.Cryptography;
 
 namespace System.Application.Models
 {
@@ -7,5 +7,7 @@ namespace System.Application.Models
         string? ApiBaseUrl { get; set; }
 
         Guid AppVersion { get; set; }
+
+        RSA RSA { get; }
     }
 }
\ No newline at end of file
diff --git a/System.Application.SteamTools.Services.CloudService/ServiceCollectionExtensions.cs b/System.Application.SteamTools.Services.CloudService/ServiceCollectionExtensions.cs
index 8bf92992e..cdb08f528 100644
--- a/System.Application.SteamTools.Services.CloudService/ServiceCollectionExtensions.cs
+++ b/System.Application.SteamTools.Services.CloudService/ServiceCollectionExtensions.cs
@@ -2,6 +2,7 @@
 using System;
 using System.Application.Services;
 using System.Application.Services.CloudService;
+using System.Net;
 
 // ReSharper disable once CheckNamespace
 namespace Microsoft.Extensions.DependencyInjection
@@ -23,7 +24,10 @@ namespace Microsoft.Extensions.DependencyInjection
                 var sc = s.GetRequiredService<CloudServiceClientBase>();
                 c.BaseAddress = new Uri(sc.ApiBaseUrl);
                 c.DefaultRequestHeaders.UserAgent.ParseAdd(sc.UserAgent);
-                c.DefaultRequestHeaders.Add(Constants.HeaderAppVersion, sc.Settings.AppVersion.ToStringN());
+                c.DefaultRequestHeaders.Add(Constants.Headers.Request.AppVersion, sc.Settings.AppVersion.ToStringN());
+#if NET5_0_OR_GREATER
+                c.DefaultRequestVersion = HttpVersion.Version20;
+#endif
             });
             services.TryAddSingleton<T>();
             services.TryAddSingleton<ICloudServiceClient>(s => s.GetRequiredService<T>());
diff --git a/System.Application.SteamTools.Services.CloudService/Services/CloudService/ApiConnection.cs b/System.Application.SteamTools.Services.CloudService/Services/CloudService/ApiConnection.cs
index c20397dd5..88ca3f167 100644
--- a/System.Application.SteamTools.Services.CloudService/Services/CloudService/ApiConnection.cs
+++ b/System.Application.SteamTools.Services.CloudService/Services/CloudService/ApiConnection.cs
@@ -10,6 +10,7 @@ using System.IO.FileFormats;
 using System.Linq;
 using System.Net.Http;
 using System.Net.Http.Headers;
+using System.Security.Cryptography;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
@@ -23,7 +24,7 @@ namespace System.Application.Services.CloudService
         readonly ILogger logger;
         readonly IHttpPlatformHelper http_helper;
         readonly IApiConnectionPlatformHelper conn_helper;
-        readonly Lazy<JsonSerializer> jsonSerializer = new Lazy<JsonSerializer>(() => new JsonSerializer());
+        readonly Lazy<JsonSerializer> jsonSerializer = new(() => new JsonSerializer());
         readonly IModelValidator validator;
 
         public ApiConnection(
@@ -86,11 +87,15 @@ namespace System.Application.Services.CloudService
         /// <param name="request">请求模型</param>
         /// <returns></returns>
         HttpContent? GetRequestContent<TRequestModel>(
-           Serializable.ImplType serializableImplType,
-           TRequestModel? request,
-           CancellationToken cancellationToken)
+            bool isSecurity,
+            Aes? aes,
+            Serializable.ImplType serializableImplType,
+            TRequestModel? request,
+            CancellationToken cancellationToken)
         {
             if (request == null) return null;
+            if (isSecurity && aes == null) throw new ArgumentNullException(nameof(aes));
+
             HttpContent? httpContent;
             if (request is IUploadFileSource uploadFile) // 上传单个文件
             {
@@ -102,6 +107,10 @@ namespace System.Application.Services.CloudService
             }
             else
             {
+                if (isSecurity && serializableImplType != Serializable.ImplType.MessagePack)
+                {
+                    serializableImplType = Serializable.ImplType.MessagePack;
+                }
                 switch (serializableImplType) // 序列化模型
                 {
                     case Serializable.ImplType.NewtonsoftJson:
@@ -110,6 +119,10 @@ namespace System.Application.Services.CloudService
                     case Serializable.ImplType.MessagePack:
                         var byteArray = Serializable.SMP(request, cancellationToken);
                         if (byteArray == null) return null;
+                        if (isSecurity)
+                        {
+                            byteArray = aes.ThrowIsNull(nameof(aes)).Encrypt(byteArray);
+                        }
                         httpContent = new ByteArrayContent(byteArray);
                         httpContent.Headers.ContentType = new MediaTypeHeaderValue(MediaTypeNames.MessagePack);
                         break;
@@ -343,7 +356,7 @@ namespace System.Application.Services.CloudService
         {
             get
             {
-                if (DI.Platform == Platform.Windows || DI.Platform == Platform.Linux || DI.Platform == Platform.Unknown) return true;
+                if (DI.Platform == Platform.Windows || (DI.Platform == Platform.Apple && DI.DeviceIdiom == DeviceIdiom.Desktop) || DI.Platform == Platform.Linux || DI.Platform == Platform.Unknown) return true;
                 return Connectivity.NetworkAccess == NetworkAccess.Internet;
             }
         }
@@ -375,7 +388,8 @@ namespace System.Application.Services.CloudService
             HttpMethod method,
             string requestUri,
             TRequestModel? requestModel,
-            bool responseContentMaybeNull)
+            bool responseContentMaybeNull,
+            bool isSecurity)
         {
             #region ModelValidator
 
@@ -396,15 +410,56 @@ namespace System.Application.Services.CloudService
             }
 
             IApiResponse<TResponseModel> responseResult;
+
+            Aes? aes = null;
+
             try
             {
+                if (isSecurity)
+                {
+                    // 行业标准加密
+                    aes = AESUtils.Create();
+                }
+
+                var serializableImplType = Serializable.ImplType.MessagePack;
+
                 using var request = new HttpRequestMessage(method, requestUri)
                 {
                     Content = GetRequestContent(
-                        Serializable.ImplType.MessagePack,
+                        isSecurity,
+                        aes,
+                        serializableImplType,
                         requestModel,
                         cancellationToken),
                 };
+
+                switch (serializableImplType)
+                {
+                    case Serializable.ImplType.NewtonsoftJson:
+                    case Serializable.ImplType.SystemTextJson:
+                        request.Headers.Accept.ParseAdd(MediaTypeNames.JSON);
+                        break;
+                    case Serializable.ImplType.MessagePack:
+                        if (isSecurity)
+                        {
+                            request.Headers.Accept.ParseAdd(MediaTypeNames.Security);
+                        }
+                        else
+                        {
+                            request.Headers.Accept.ParseAdd(MediaTypeNames.MessagePack);
+                        }
+                        break;
+                    default:
+                        throw new ArgumentOutOfRangeException(nameof(serializableImplType), serializableImplType, null);
+                }
+
+                if (isSecurity)
+                {
+                    var skey_bytes = aes.ThrowIsNull(nameof(aes)).ToParamsByteArray();
+                    var skey_str = conn_helper.RSA.EncryptToString(skey_bytes);
+                    request.Headers.Add(Constants.Headers.Request.SecurityKey, skey_str);
+                }
+
                 await SetRequestHeaderAuthorization(request);
                 var client = conn_helper.CreateClient();
                 using var response = await client.SendAsync(request,
@@ -420,37 +475,47 @@ namespace System.Application.Services.CloudService
                 {
                     if (!isApi && typeof(TResponseModel) == typeof(byte[]))
                     {
-                        var bytes = await response.Content.ReadAsByteArrayAsync().ConfigureAwait(false);
+                        var bytes = await response.Content.ReadAsByteArrayAsync(cancellationToken).ConfigureAwait(false);
                         responseResult = ApiResponse.Code(code,
                             content: (TResponseModel)(object)bytes);
                     }
                     else if (!isApi && typeof(TResponseModel) == typeof(string))
                     {
-                        var str = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
+                        var str = await response.Content.ReadAsStringAsync(cancellationToken).ConfigureAwait(false);
                         responseResult = ApiResponse.Code(code,
                             content: (TResponseModel)(object)str);
                     }
                     else
                     {
-                        var mime = response.Content.Headers.ContentType.MediaType;
+                        var rspIsCiphertext = false;
+
+                        var mime = response.Content.Headers.ContentType?.MediaType;
+
+                        if (mime == MediaTypeNames.Security)
+                        {
+                            mime = MediaTypeNames.MessagePack;
+                            rspIsCiphertext = true;
+                        }
+
                         switch (mime)
                         {
                             case MediaTypeNames.JSON:
                                 {
-                                    using var stream = await response.Content
-                                        .ReadAsStreamAsync().ConfigureAwait(false);
+                                    if (rspIsCiphertext)
+                                    {
+                                        throw new NotSupportedException("At present, JSON does not implement security on the server side, so this cannot happen.");
+                                    }
+                                    using var stream = await response.Content.ReadAsStreamAsync(cancellationToken).ConfigureAwait(false);
                                     using var reader = new StreamReader(stream, Encoding.UTF8);
                                     using var json = new JsonTextReader(reader);
-                                    responseResult = ApiResponse
-                                        .Deserialize<TResponseModel>(jsonSerializer.Value, json);
+                                    responseResult = ApiResponse.Deserialize<TResponseModel>(jsonSerializer.Value, json);
                                 }
                                 break;
                             case MediaTypeNames.MessagePack:
                                 {
-                                    using var stream = await response.Content
-                                        .ReadAsStreamAsync().ConfigureAwait(false);
-                                    responseResult = await ApiResponse
-                                        .DeserializeAsync<TResponseModel>(stream, cancellationToken);
+                                    using var stream = await response.Content.ReadAsStreamAsync(cancellationToken).ConfigureAwait(false);
+                                    using CryptoStream? cryptoStream = rspIsCiphertext ? new CryptoStream(stream, aes.ThrowIsNull(nameof(aes)).CreateDecryptor(), CryptoStreamMode.Read) : null;
+                                    responseResult = await ApiResponse.DeserializeAsync<TResponseModel>(rspIsCiphertext ? cryptoStream.ThrowIsNull(nameof(cryptoStream)) : stream, cancellationToken);
                                 }
                                 break;
                             default:
@@ -465,6 +530,10 @@ namespace System.Application.Services.CloudService
                 logger.LogError(ex, nameof(ApiConnection));
                 responseResult = ApiResponse.Code<TResponseModel>(GetCodeByException(ex));
             }
+            finally
+            {
+                aes?.Dispose();
+            }
             await GlobalResponseIntercept(
                 isApi,
                 method,
@@ -564,7 +633,7 @@ namespace System.Application.Services.CloudService
             return responseResult;
         }
 
-        public async Task<IApiResponse<TResponseModel>> SendAsync<TRequestModel, TResponseModel>(CancellationToken cancellationToken, HttpMethod method, string requestUri, TRequestModel? request, bool responseContentMaybeNull = false)
+        public async Task<IApiResponse<TResponseModel>> SendAsync<TRequestModel, TResponseModel>(CancellationToken cancellationToken, HttpMethod method, string requestUri, TRequestModel? request, bool responseContentMaybeNull, bool isSecurity)
         {
             var rsp = await SendCoreAsync<TRequestModel, TResponseModel>(
                 isApi: true,
@@ -572,7 +641,8 @@ namespace System.Application.Services.CloudService
                 method,
                 requestUri,
                 requestModel: request,
-                responseContentMaybeNull);
+                responseContentMaybeNull,
+                isSecurity);
             return rsp;
         }
 
@@ -584,7 +654,8 @@ namespace System.Application.Services.CloudService
                 HttpMethod.Get,
                 requestUri,
                 requestModel: null,
-                responseContentMaybeNull: false);
+                responseContentMaybeNull: false,
+                isSecurity: false);
             return rsp;
         }
 
@@ -596,11 +667,12 @@ namespace System.Application.Services.CloudService
                 HttpMethod.Get,
                 requestUri,
                 requestModel: null,
-                responseContentMaybeNull: false);
+                responseContentMaybeNull: false,
+                isSecurity: false);
             return rsp;
         }
 
-        public async Task<IApiResponse> SendAsync<TRequestModel>(CancellationToken cancellationToken, HttpMethod method, string requestUri, TRequestModel? request)
+        public async Task<IApiResponse> SendAsync<TRequestModel>(CancellationToken cancellationToken, HttpMethod method, string requestUri, TRequestModel? request, bool isSecurity)
         {
             var rsp = await SendCoreAsync<TRequestModel, object>(
                 isApi: true,
@@ -608,7 +680,8 @@ namespace System.Application.Services.CloudService
                 method,
                 requestUri,
                 requestModel: request,
-                responseContentMaybeNull: true);
+                responseContentMaybeNull: true,
+                isSecurity);
             return rsp;
         }
 
@@ -620,11 +693,12 @@ namespace System.Application.Services.CloudService
                 method,
                 requestUri,
                 requestModel: null,
-                responseContentMaybeNull: true);
+                responseContentMaybeNull: true,
+                isSecurity: false);
             return rsp;
         }
 
-        public async Task<IApiResponse<TResponseModel>> SendAsync<TResponseModel>(CancellationToken cancellationToken, HttpMethod method, string requestUri, bool responseContentMaybeNull = false)
+        public async Task<IApiResponse<TResponseModel>> SendAsync<TResponseModel>(CancellationToken cancellationToken, HttpMethod method, string requestUri, bool responseContentMaybeNull, bool isSecurity)
         {
             var rsp = await SendCoreAsync<object, TResponseModel>(
                 isApi: true,
@@ -632,7 +706,8 @@ namespace System.Application.Services.CloudService
                 method,
                 requestUri,
                 requestModel: null,
-                responseContentMaybeNull);
+                responseContentMaybeNull,
+                isSecurity);
             return rsp;
         }
     }
diff --git a/System.Application.SteamTools.Services.CloudService/Services/CloudService/CloudServiceClientBase.cs b/System.Application.SteamTools.Services.CloudService/Services/CloudService/CloudServiceClientBase.cs
index 45692c9a6..158288e66 100644
--- a/System.Application.SteamTools.Services.CloudService/Services/CloudService/CloudServiceClientBase.cs
+++ b/System.Application.SteamTools.Services.CloudService/Services/CloudService/CloudServiceClientBase.cs
@@ -5,6 +5,7 @@ using System.Application.Models;
 using System.Application.Services.CloudService.Clients;
 using System.Application.Services.CloudService.Clients.Abstractions;
 using System.Net.Http;
+using System.Security.Cryptography;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -31,6 +32,8 @@ namespace System.Application.Services.CloudService
 
         internal ICloudServiceSettings Settings => settings;
 
+        RSA IApiConnectionPlatformHelper.RSA => Settings.RSA;
+
         protected sealed override string? ClientName => ClientName_;
 
         public CloudServiceClientBase(
diff --git a/System.Application.SteamTools.Services.CloudService/Services/CloudService/IApiConnection.cs b/System.Application.SteamTools.Services.CloudService/Services/CloudService/IApiConnection.cs
index c11eaf03c..bb104ad77 100644
--- a/System.Application.SteamTools.Services.CloudService/Services/CloudService/IApiConnection.cs
+++ b/System.Application.SteamTools.Services.CloudService/Services/CloudService/IApiConnection.cs
@@ -52,7 +52,8 @@ namespace System.Application.Services.CloudService
             HttpMethod method,
             string requestUri,
             TRequestModel? request,
-            bool responseContentMaybeNull = false);
+            bool responseContentMaybeNull = false,
+            bool isSecurity = false);
 
         /// <summary>
         /// RequestModel(调用服务端接口)
@@ -67,7 +68,8 @@ namespace System.Application.Services.CloudService
             CancellationToken cancellationToken,
             HttpMethod method,
             string requestUri,
-            TRequestModel? request);
+            TRequestModel? request,
+            bool isSecurity = false);
 
         /// <summary>
         /// NoModel(调用服务端接口)
@@ -93,7 +95,8 @@ namespace System.Application.Services.CloudService
             CancellationToken cancellationToken,
             HttpMethod method,
             string requestUri,
-            bool responseContentMaybeNull = false);
+            bool responseContentMaybeNull = false,
+            bool isSecurity = false);
 
         #endregion
     }
diff --git a/System.Application.SteamTools.Services.CloudService/Services/CloudService/IApiConnectionPlatformHelper.cs b/System.Application.SteamTools.Services.CloudService/Services/CloudService/IApiConnectionPlatformHelper.cs
index b6242d930..1807423f7 100644
--- a/System.Application.SteamTools.Services.CloudService/Services/CloudService/IApiConnectionPlatformHelper.cs
+++ b/System.Application.SteamTools.Services.CloudService/Services/CloudService/IApiConnectionPlatformHelper.cs
@@ -1,6 +1,7 @@
 using System.Application.Columns;
 using System.Application.Models;
 using System.Net.Http;
+using System.Security.Cryptography;
 using System.Threading.Tasks;
 
 namespace System.Application.Services.CloudService
@@ -33,5 +34,7 @@ namespace System.Application.Services.CloudService
         void ShowResponseErrorMessage(string message);
 
         HttpClient CreateClient();
+
+        RSA RSA { get; }
     }
 }
\ No newline at end of file
diff --git a/System.Application.SteamTools.Services.CloudService/System.Application.SteamTools.Services.CloudService.csproj b/System.Application.SteamTools.Services.CloudService/System.Application.SteamTools.Services.CloudService.csproj
index e018ee975..d2b42aa7d 100644
--- a/System.Application.SteamTools.Services.CloudService/System.Application.SteamTools.Services.CloudService.csproj
+++ b/System.Application.SteamTools.Services.CloudService/System.Application.SteamTools.Services.CloudService.csproj
@@ -1,7 +1,7 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.1</TargetFramework>
+    <TargetFrameworks>netstandard2.1;net5.0</TargetFrameworks>
     <RootNamespace>System.Application</RootNamespace>
   </PropertyGroup>
 
diff --git a/System.Common.CoreLib/MediaTypeNames.cs b/System.Common.CoreLib/MediaTypeNames.cs
index 29a821d58..a20b91c0d 100644
--- a/System.Common.CoreLib/MediaTypeNames.cs
+++ b/System.Common.CoreLib/MediaTypeNames.cs
@@ -54,5 +54,7 @@
         public const string XML = "text/xml";
 
         public const string XML_APP = "application/xml";
+
+        public const string Security = "application/vnd.sapi+x-msgpack";
     }
 }
\ No newline at end of file