private static byte[] CreateSequence(Nintendo.Sead.Random random)
{
// Create byte array
byte[] sequence = new byte[16];
// Create each byte
for (int i = 0; i < sequence.Length; i++)
{
// Create empty byte string
string byteString = "";
// Get characters from key material
byteString += KeyMaterialString[(int)(random.GetUInt32() >> 24)];
byteString += KeyMaterialString[(int)(random.GetUInt32() >> 24)];
// Parse the resulting byte
sequence[i] = Convert.ToByte(byteString, 16);
}
// Return the sequence
return(sequence);
}
public static void Decrypt(Stream inputStream, Stream outputStream, string gamePath)
{
// Read the entire file into an array
byte[] encryptedData = new byte[inputStream.Length - 8];
inputStream.Seek(0, SeekOrigin.Begin);
inputStream.Read(encryptedData, 0, (int)inputStream.Length - 8);
// Generate a CRC32 over the game path
Crc32 crc32 = new Crc32();
uint seed = crc32.Get(Encoding.ASCII.GetBytes(gamePath));
// Create a new SeadRandom instance using the seed
Nintendo.Sead.Random seadRandom = new Nintendo.Sead.Random(seed);
// Create the encryption key and IV
byte[] encryptionKey = CreateSequence(seadRandom);
byte[] iv = CreateSequence(seadRandom);
// Generate a KeyParameter instance
KeyParameter parameter = new KeyParameter(encryptionKey);
// Initialize the AES-CBC cipher
IBufferedCipher cipher = CipherUtilities.GetCipher("AES/CBC/NoPadding");
cipher.Init(false, new ParametersWithIV(parameter, iv));
// Return the decrypted bytes
byte[] output = cipher.DoFinal(encryptedData);
// Seek to the beginning
outputStream.Seek(0, SeekOrigin.Begin);
// Write to the output stream
outputStream.Write(output, 0, output.Length);
// Seek back to the beginning
outputStream.Seek(0, SeekOrigin.Begin);
}
