public static void DecryptNgxRom(string inPath, string outPath)
{
File.Copy(inPath, outPath, true);
using (var fs = File.Open(outPath, FileMode.Open, FileAccess.ReadWrite))
{
BinaryReader br = new BinaryReader(fs);
fs.Seek(-8, SeekOrigin.End);
int unencryptedStart = br.ReadInt32() ^ 0x12345678;
int unencryptedEnd = br.ReadInt32() ^ 0x12345678;
int keyLength;
byte[] keyData = GetNgxRomKey(br, unencryptedStart, unencryptedEnd, out keyLength);
BurnCacheHeader header = null;
CryptNgxRom(fs, ref header, keyData, keyLength);
// Swap sprite and text blocks
BinaryWriter bw = new BinaryWriter(fs);
fs.Seek(header.Blocks[1].Offset, SeekOrigin.Begin);
byte[] textBlock = br.ReadBytes((int)header.GetLength(1));
byte[] spriteBlock = br.ReadBytes((int)header.GetLength(2));
fs.Seek(header.Blocks[1].Offset, SeekOrigin.Begin);
bw.Write(spriteBlock);
header.Blocks[2].Offset = (uint)fs.Position;
bw.Write(textBlock);
// Update header
fs.Seek(0, SeekOrigin.Begin);
header.Write(bw);
fs.SetLength(fs.Length - 8);
}
}
static void CryptNgxRom(Stream fs, ref BurnCacheHeader header, byte[] keyData, int keyLength)
{
BinaryReader br = new BinaryReader(fs);
BinaryWriter bw = new BinaryWriter(fs);
// Crypt cache header
fs.Seek(0, SeekOrigin.Begin);
byte[] cacheHeader = br.ReadBytes(0x100);
for (int i = 0; i < cacheHeader.Length; ++i)
{
cacheHeader[i] ^= keyData[i % keyLength];
}
fs.Seek(0, SeekOrigin.Begin);
bw.Write(cacheHeader);
if (header == null)
{
using (MemoryStream ms = new MemoryStream(cacheHeader))
{
BinaryReader hbr = new BinaryReader(ms);
header = new BurnCacheHeader();
header.Read(hbr);
}
}
// Encryption map (key index -> cache block)
Dictionary <int, int> encryptionMap = new Dictionary <int, int>
{
{ 1, 0 }, // Code
{ 2, 3 }, // PCM A
{ 3, 4 }, // PCM B
{ 4, 5 }, // Sprite Attr
{ 5, 6 } // Text Attr
};
foreach (var pair in encryptionMap)
{
CryptNeoGeoBlock(fs, header.Blocks[pair.Value].Offset, header.GetLength(pair.Value), keyData,
pair.Key * ROM_KEY_OFFSET_MULTIPLE, keyLength);
}
}
