Add project files.

AssetStudio/Game/Crypto/Blk.cs

@@ -0,0 +1,76 @@
+using System;
+
+namespace AssetStudio
+{
+    public static class Blk
+    {
+        private const int KeySize = 0x1000;
+        private const int SeedBlockSize = 0x800;
+
+        public static byte[] ExpansionKey;
+        public static byte[] SBox;
+        public static byte[] ConstKey;
+        public static ulong ConstVal;
+
+        public static byte[] Decrypt(FileReader reader)
+        {
+            reader.Endian = EndianType.LittleEndian;
+
+            var signature = reader.ReadStringToNull();
+            if (signature != "blk")
+                throw new Exception("not a blk");
+
+            var count = reader.ReadInt32();
+            var key = reader.ReadBytes(count);
+            reader.Position += count;
+            var seedSize = Math.Min(reader.ReadInt16(), SBox == null ? SeedBlockSize : SeedBlockSize * 2);
+
+            var dataSize = (int)(reader.BaseStream.Length - reader.BaseStream.Position);
+            var buffer = reader.ReadBytes(dataSize);
+
+            long keySeed = -1;
+            for (int i = 0; i < seedSize / 8; i++)
+            {
+                keySeed ^= BitConverter.ToInt64(buffer, i * 8);
+            }
+
+            DecryptKey(key);
+
+            var keyLow = BitConverter.ToUInt64(key, 0);
+            var keyHigh = BitConverter.ToUInt64(key, 8);
+            var seed = keyLow ^ keyHigh ^ (ulong)keySeed ^ ConstVal;
+
+            var xorpad = new byte[KeySize];
+            var rand = new MT19937_64(seed);
+            for (int i = 0; i < KeySize / 8; i++)
+            {
+                Buffer.BlockCopy(BitConverter.GetBytes(rand.Int63()), 0, xorpad, i * 8, 8);
+            }
+
+            for (int i = 0; i < dataSize; i++)
+            {
+                buffer[i] ^= xorpad[i % KeySize];
+            }
+
+            return buffer;
+        }
+
+        private static void DecryptKey(byte[] key)
+        {
+            if (SBox != null)
+            {
+                for (int i = 0; i < 0x10; i++)
+                {
+                    key[i] = SBox[(i % 4 * 0x100) | key[i]];
+                }
+            }
+
+            AES.Decrypt(key, ExpansionKey);
+
+            for (int i = 0; i < 0x10; i++)
+            {
+                key[i] ^= ConstKey[i];
+            }
+        }
+    }
+}