Initial pass at Encrypted CTB format support for UVTools

Helpers.cs: Added new SHA256 and AES helper methods

FileFormat.cs: Add as available file format, does not appear in the UI

CTBEncryptedFile.cs: New FileFormat implementation for these encrypted CTB files. Keys are left as an excercise

UVtools.Core/FileFormats/FileFormat.cs

@@ -278,6 +278,7 @@ namespace UVtools.Core.FileFormats
             new SL1File(),      // Prusa SL1
             new ChituboxZipFile(), // Zip
             new ChituboxFile(), // cbddlp, cbt, photon
+            new CTBEncryptedFile(), // Mars 3, Epax 5k
             new PhotonSFile(), // photons
             new PHZFile(), // phz
             new FDGFile(), // fdg

UVtools.Core/Helpers.cs

@@ -57,6 +57,47 @@ namespace UVtools.Core
             return Convert.ToBase64String(SHA1.ComputeHash(input));
         }
 
+        public static SHA256 SHA256 { get; } = SHA256.Create();
+        public static byte[] ComputeSHA256Hash(byte[] input)
+        {
+            return SHA256.ComputeHash(input);
+        }
+
+        public static byte[] AesCryptBytes(byte[] data, byte[] key, CipherMode mode, PaddingMode paddingMode, bool encrypt, byte[] iv = null)
+        {
+            if (data.Length % 0x10 != 0)
+            {
+                byte[] temp = new byte[((data.Length / 0x10) + 1) * 0x10];
+                Array.Copy(data, 0, temp, 0, data.Length);
+                data = temp;
+            }
+
+
+            AesManaged aes = new AesManaged();
+
+            aes.KeySize = key.Length * 8;
+            aes.Key = key;
+            aes.Padding = paddingMode;
+            aes.Mode = mode;
+            if (iv != null)
+            {
+                aes.IV = iv;
+            }
+            ICryptoTransform cryptor = encrypt ? aes.CreateEncryptor() : aes.CreateDecryptor();
+
+            byte[] outputBuffer = null;
+            using (MemoryStream msDecrypt = new MemoryStream(data))
+            {
+                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, cryptor, CryptoStreamMode.Read))
+                {
+                    outputBuffer = new byte[data.Length];
+                    csDecrypt.Read(outputBuffer, 0, data.Length);
+                }
+            }
+
+            return outputBuffer;
+        }
+
         public static bool SetPropertyValue(PropertyInfo attribute, object obj, string value)
         {
             var name = attribute.PropertyType.Name.ToLower();