/// <summary>
/// Decrypts data from server-side packets (sent from servers to clients.)
/// </summary>
/// <param name="source">The encrypted packet data.</param>
/// <param name="key">Key to decrypt with.</param>
/// <returns>The decrypted packet data.</returns>
/// <exception cref="ArgumentOutOfRangeException">
/// Thrown if the key is invalid or the packet data is too short.
/// </exception>
public static byte[] Decrypt(byte[] source, byte key)
{
if (key >= 0x10)
{
throw new ArgumentOutOfRangeException(nameof(key), $"Key too large ({key} >= 0x10)");
}
if (source.Length < 8)
{
throw new ArgumentOutOfRangeException(nameof(source), $"Packet too small ({source.Length} < 8)");
}
var oracleByte = CryptoOracle.CryptTable2[(key << 8) + source[0]];
var buffer = (byte[])source.Clone();
buffer[7] ^= oracleByte;
for (var i = 10; i < source.Length; i++)
{
buffer[i] ^= buffer[i - 4];
}
var compressedData = new byte[source.Length - 8];
Array.Copy(buffer, 8, compressedData, 0, source.Length - 8);
return(MiniLzo.Decompress(compressedData));
}
