This disk key is stored on the hidden sector of the DVD along with a a table containing the disk key encrypted will each of the 409 possible player keys. It also holds the disk key encrypted with the disk key. The player decrypts the appropriate entry in the table and then verifies that it has correctly decoding the disk key, by decoding the encrypted disk key. The result, should be the disk key. That is to say that the decryption of the disk key, using the disk key, should prove to be the identity function.
Players have more than one player key, so if the operation fails, they try again with an alternate.
So, let's begin to talk about how the encryption works. We're going to begin with a little bit of background, then look at how data is encrypted, and then look at how keys, such as the title key above, are encrypted. One technique used to encode a stream is to XOR it with a pseudo-random bit stream. If this random-looking bit stream can be regenerated by the receiver of the message, the receiver will be able to decode the message by repeating the XOR operation. The LFSR is one popular technique for generating a pseudo-random bit stream.