Are some arcade ROMs encrypted?
Yes, encryption is fairly common in arcade games but the ROM dumping process is no different. It is the job of the emulator to decrypt the ROM and make it playable (just like part of the arcade board decrypts the ROM). Sometimes the encryption algorithm is known and can implemented into emulators but in the case of CPS-2 an XOR file is used to un-encrypt ROM data. This XOR file is created by tricking a real CPS-2 board into decrypting the ROMs and sending the un-encrypted data to a PC. By comparing the encrypted data and un-encrypted data an XOR file can then created for the emulators to use. In case you haven’t guessed, encrypted data is decrypted by simply XORing the data in the XOR file (a simple binary operator).
