diff --git a/LICENSE.txt b/LICENSE.txt
index 46bfdcb4..4be89ce9 100644
--- a/LICENSE.txt
+++ b/LICENSE.txt
@@ -624,6 +624,7 @@ copy of the Program in return for a fee.
                      END OF TERMS AND CONDITIONS
 
 Copyright (C) 2015 clowwindy <clowwindy42@gmail.com>
+Copyright (C) 2020 Shadowsocks Project <https://shadowsocks.org>
 
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
diff --git a/shadowsocks-csharp/Controller/Service/PACServer.cs b/shadowsocks-csharp/Controller/Service/PACServer.cs
index 7833e01a..57e64ca2 100644
--- a/shadowsocks-csharp/Controller/Service/PACServer.cs
+++ b/shadowsocks-csharp/Controller/Service/PACServer.cs
@@ -1,15 +1,10 @@
-using System;
-using System.Collections;
-using System.Globalization;
-using System.IO;
+using Shadowsocks.Encryption;
+using Shadowsocks.Model;
+using Shadowsocks.Util;
+using System;
 using System.Net;
 using System.Net.Sockets;
 using System.Text;
-using Shadowsocks.Encryption;
-using Shadowsocks.Model;
-using Shadowsocks.Properties;
-using Shadowsocks.Util;
-using System.Threading.Tasks;
 using System.Web;
 
 namespace Shadowsocks.Controller
@@ -53,12 +48,7 @@ namespace Shadowsocks.Controller
 
         private static string GetHash(string content)
         {
-            var contentBytes = Encoding.ASCII.GetBytes(content);
-            using (var md5 = System.Security.Cryptography.MD5.Create())
-            {
-                var md5Bytes = md5.ComputeHash(contentBytes);
-                return HttpServerUtility.UrlTokenEncode(md5Bytes);
-            };
+            return HttpServerUtility.UrlTokenEncode(MbedTLS.MD5(Encoding.ASCII.GetBytes(content)));
         }
 
         public override bool Handle(byte[] firstPacket, int length, Socket socket, object state)
diff --git a/shadowsocks-csharp/Encryption/EncryptorFactory.cs b/shadowsocks-csharp/Encryption/EncryptorFactory.cs
index 169a67ce..fcae221a 100644
--- a/shadowsocks-csharp/Encryption/EncryptorFactory.cs
+++ b/shadowsocks-csharp/Encryption/EncryptorFactory.cs
@@ -70,7 +70,7 @@ namespace Shadowsocks.Encryption
         {
             if (method.IsNullOrEmpty())
             {
-                method = "aes-256-cfb";
+                method = Model.Server.DefaultMethod;
             }
 
             method = method.ToLowerInvariant();
diff --git a/shadowsocks-csharp/Model/Server.cs b/shadowsocks-csharp/Model/Server.cs
index 88f72c2c..6e08f50e 100755
--- a/shadowsocks-csharp/Model/Server.cs
+++ b/shadowsocks-csharp/Model/Server.cs
@@ -11,6 +11,9 @@ namespace Shadowsocks.Model
     [Serializable]
     public class Server
     {
+        public const string DefaultMethod = "chacha20-ietf-poly1305";
+        public const int DefaultPort = 8388;
+
         #region ParseLegacyURL
         public static readonly Regex
             UrlFinder = new Regex(@"ss://(?<base64>[A-Za-z0-9+-/=_]+)(?:#(?<tag>\S+))?", RegexOptions.IgnoreCase),
@@ -69,8 +72,8 @@ namespace Shadowsocks.Model
         public Server()
         {
             server = "";
-            server_port = 8388;
-            method = "chacha20-ietf-poly1305";
+            server_port = DefaultPort;
+            method = DefaultMethod;
             plugin = "";
             plugin_opts = "";
             plugin_args = "";
diff --git a/shadowsocks-csharp/Properties/AssemblyInfo.cs b/shadowsocks-csharp/Properties/AssemblyInfo.cs
index bbb3a28a..b140accf 100755
--- a/shadowsocks-csharp/Properties/AssemblyInfo.cs
+++ b/shadowsocks-csharp/Properties/AssemblyInfo.cs
@@ -11,7 +11,7 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyConfiguration("")]
 [assembly: AssemblyCompany("")]
 [assembly: AssemblyProduct("Shadowsocks")]
-[assembly: AssemblyCopyright("clowwindy & community 2019")]
+[assembly: AssemblyCopyright("clowwindy & community 2020")]
 [assembly: AssemblyTrademark("")]
 [assembly: AssemblyCulture("")]
 
diff --git a/shadowsocks-csharp/View/ConfigForm.cs b/shadowsocks-csharp/View/ConfigForm.cs
index 8151dc58..379edc29 100755
--- a/shadowsocks-csharp/View/ConfigForm.cs
+++ b/shadowsocks-csharp/View/ConfigForm.cs
@@ -316,7 +316,7 @@ namespace Shadowsocks.View
             IPTextBox.Text = server.server;
             ServerPortTextBox.Text = server.server_port.ToString();
             PasswordTextBox.Text = server.password;
-            EncryptionSelect.Text = server.method ?? "aes-256-cfb";
+            EncryptionSelect.Text = server.method ?? Server.DefaultMethod;
             PluginTextBox.Text = server.plugin;
             PluginOptionsTextBox.Text = server.plugin_opts;
             PluginArgumentsTextBox.Text = server.plugin_args;