Blu-ray uses complex DRM schemes to protect their discs from unauthorized copying. DRM has been a controversial subject since the DVD-era.

It's uncommon for commercial BD discs to be unencrypted or DRM-free, but it's up to the studio/developer if they want to publish a DRM-free disc*. Here are the DRM schemes that Blu-ray uses, each one is very unique and many individuals have been successful at cracking these.

Advanced Access Content System (AACS) is part of the Blu-ray DRM and it's an advanced and complex cryptic DRM that works by encrypting the content on the disc using a combination of symmetric and asymmetric key cryptography. The AACS cryptic system is overwhelmingly complex to explain, so I'll just cut it short. The system also employs digital signatures and a key revocation system to protect against unauthorized copying and distribution. It encrypts content under one or more title keys using the Advanced Encryption Standard (AES). To view a BD movie, the player must first decrypt the content on the disc. The decryption process is somewhat complex. The disc contains 4 items—the Media Key Block (MKB), the Volume ID, the Encrypted Title Keys, and the Encrypted Content. Think of the keys like the offline activation keys for DVD-ROM games, except the player is the one reading and activating them, not you. 

AACS decryption process

There have been several successful unauthorized cracks on it, including the very famous  AACS encryption key controversy and  PS3's compromised private key in 2007. AACS was created by a consortium of companies known as the AACS Licensing Authority (AACS LA), which includes major players in the entertainment and tech industry, such as Sony, Disney, Warner Bros. Intel, Microsoft, Panasonic, IBM, and Toshiba.

 Each year new keys are regularly published which makes this a game of cat and mouse for hackers. Here's the famous encryption key, one of the most banned numbers back in the day:  09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 . 

    A compromised player can still be used to view old discs, but not newer releases without encryption keys for a compromised player. If other players become cracked, revoking access could result in legitimate users of compromised players needing to upgrade or replace their software or firmware to be able to watch new discs.

Many individuals who wish to watch BD-ROMs on their computer typically use either Windows or Linux in conjunction with the VLC player. Although the VLC player can successfully play older physical BD-ROMS (or unencrypted ISO files) with the use of older keys, it is unable to play newer ones without obtaining new keys. The process of obtaining these new keys can prove to be quite challenging.

Volume IDs are unique identifiers or serial numbers that are stored on pressed pre-recorded discs with special hardware. They cannot be physically duplicated on consumers' recordable media. The point of this is to prevent simple bit-by-bit copies since the Volume ID is required (though not sufficient) for decoding content. On Blu-ray discs, the Volume ID is stored in the BD-ROM Mark.

Here's an example of a BD-ROM title with unique keys for the 2007 U.S. release of Robocop:

• CPS Unit  Key (Title Key):  2CC3A36907E90C22E0B0B16856DB12AD121991EA
• Volume Unit Key:  98B02655F0A387AFDF636352875E0AB6
• Media Key:  5B90FE346BBF4CA41570D3F25CAD9B4A 

AACS: Directory containing the Blu-ray's DRM AACS decryption files.

• MKB_RW.inf file: Read/Write Media Key Block.
• Content001.cer
• Content002.cer
• ContentHash001.tbl
• ContentHash002.tbl
• ContentRevocation.lst
• CPSUnit0000x.cci: CPS Unit Usage files.
• mcmf.xml
• MKB_RO.inf
• MKB_RW.inf
• SKBx.inf
• Unit_Key_RO.inf: AACS CPS Unit Key.
• DUPLICATE: Directory of duplicated AACS files.

Author(s) : Æ Firestone