Module auth 

CSS drive authentication — full key hierarchy.

Protocol:

1. Bus authentication (challenge-response) → bus key
2. Read disc key block (READ DVD STRUCTURE) → XOR with bus key → decrypt with player keys → disc key
3. Read title key (REPORT KEY format 0x04) → XOR with bus key → decrypt with disc key → title key

Functions

authenticate

Perform CSS bus authentication only.

authenticate_and_read_title_key

Full CSS key extraction: bus auth → disc key → title key.

test_crypt_key

Exposed for testing only.