Added ChangeSalt argument function

Lain/CryLain.cs

@@ -1,8 +1,11 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
+using System.Runtime.Serialization.Formatters.Binary;
 using System.Security;
 using System.Security.Cryptography;
 using System.Text;
+using System.Windows.Forms;
 
 namespace Lain
 {
@@ -21,6 +24,15 @@ internal static string HashKey(string key)
             }
         }
 
+        private static string HashKeyCustomSalt(string key, string customSalt)
+        {
+            using (SHA256 sha256 = SHA256.Create())
+            {
+                byte[] hashed = sha256.ComputeHash(Encoding.UTF8.GetBytes(key + customSalt));
+                return Convert.ToBase64String(hashed);
+            }
+        }
+
         internal static SecureString ToSecureString(string key)
         {
             SecureString ss = new SecureString();
@@ -80,6 +92,31 @@ internal string Decrypt(string key, string data)
             return decrypted;
         }
 
+        internal static bool ChangeSalt(string toSalt, string oldKey)
+        {
+            string _newKey = CryLain.HashKeyCustomSalt(oldKey, toSalt);
+
+            if (string.IsNullOrEmpty(oldKey) || string.IsNullOrEmpty(_newKey)) return false;
+
+            try
+            {
+                File.WriteAllText(Required.LainSerial, _newKey);
+                return true;
+            }
+            catch (Exception err)
+            {
+                MessageBox.Show(err.Message, "Lain", MessageBoxButtons.OK, MessageBoxIcon.Information);
+                Environment.Exit(0);
+                return false;
+            }
+            finally
+            {
+                oldKey = string.Empty;
+                _newKey = string.Empty;
+                toSalt = string.Empty;
+            }
+        }
+
         private string Protect(string plainText, byte[] Key, byte[] IV)
         {
             if (plainText == null || plainText.Length <= 0)

Lain/Forms/MainForm.cs

@@ -162,12 +162,7 @@ private void CheckForUpdate()
                             File.Move(tempFile, appFile);
 
                             // BYPASS SINGLE-INSTANCE MECHANISM
-                            if (Program.MUTEX != null)
-                            {
-                                Program.MUTEX.ReleaseMutex();
-                                Program.MUTEX.Dispose();
-                                Program.MUTEX = null;
-                            }
+                            Program.RestartLain();
 
                             Application.Restart();
                         }