diff --git a/app/src/main/java/com/pkusz/min_vpn_client/GlobalSetting.java b/app/src/main/java/com/pkusz/min_vpn_client/GlobalSetting.java
index 8dba707..0a29b7f 100644
--- a/app/src/main/java/com/pkusz/min_vpn_client/GlobalSetting.java
+++ b/app/src/main/java/com/pkusz/min_vpn_client/GlobalSetting.java
@@ -1,5 +1,10 @@
 package com.pkusz.min_vpn_client;
+// 本类存储一些静态布尔型常量，用于控制APP的一些参数
+// 这些参数将不允许用户进行修改，只作为APP开发者的调试参数而存在
 
 public class GlobalSetting {
-    public static boolean openBiometric = false;
+    // public static boolean openBiometric = false;
+
+    // 控制与VPNServer的对称加密通信方法，true表示使用sm4，false表示使用AES
+    public static boolean isSM4 =false; 
 }
diff --git a/app/src/main/java/com/pkusz/min_vpn_client/services/MINVpnService.java b/app/src/main/java/com/pkusz/min_vpn_client/services/MINVpnService.java
index a303d2f..017cae2 100644
--- a/app/src/main/java/com/pkusz/min_vpn_client/services/MINVpnService.java
+++ b/app/src/main/java/com/pkusz/min_vpn_client/services/MINVpnService.java
@@ -24,6 +24,7 @@ import android.widget.Toast;
 import androidx.annotation.NonNull;
 import androidx.annotation.RequiresApi;
 
+import com.pkusz.min_vpn_client.GlobalSetting;
 import com.pkusz.min_vpn_client.R;
 import com.pkusz.min_vpn_client.activity.main.MainActivity;
 import com.pkusz.min_vpn_client.model.MINVpnSettingAPI;
@@ -153,7 +154,7 @@ public class MINVpnService extends VpnService implements Handler.Callback{
 
         minVpnConnection = new MINVpnConnection(
                 this, mNextConnectionId.getAndIncrement(), server, port, secret,
-                proxyHost, proxyPort, allow, packages,false);
+                proxyHost, proxyPort, allow, packages, GlobalSetting.isSM4);
 
         // 对vpn connection进行各种监听设置，并启动执行其run函数
         startConnection(minVpnConnection);