Media Key Block
Encyclopedia
The Media Key Block is one of the keys that are included inside the copying protection system (DRM
) AACS
. This system is used to protect Blu-ray and HD DVD
formats from being copied. The system has been developed by big companies from the film industry and the electronics industry like: IBM
, Intel, Microsoft
, Matsushita (Panasonic), Sony
, Toshiba
, The Walt Disney Company
and Warner Bros.
.
The MKB key is found in the physical support (the disc) together with the content of the disc encrypted. The MKB has the function of validating the reproduction devices on which the disc is being played and obtaining, from the devices codes, the key that will allow the decryption of the disc content. That is the Media key (Km).
(s) and the MKB. The MKB is also found encrypted in the disc to prevent it from being extracted off the disc and being manipulated and/or reproduced by another non authorized device.
The reproduction device will have available its own keys, uniques for each model, called Device Keys
. These keys are conceded by the AACS organization. In the moment of the reproduction, one of these keys will decrypt the MKB contained on the disc and as a result of this process we obtain the Media key.
The Media key is combined together with the VID (Volume ID) and as a result we obtain the Volume Unique Key (Kvu). With the Kvu we are able to decrypt the Encrypted Title Key and obtain the Title keys which finally allows to decrypt the content of the disc and view it.
This way the system can protect contents from being viewed in devices that have not been authorized. Therefore, the system allows modifying the MKB in future relaunch of a determined content in order to select the devices in which this content can be viewed.
Even though it seems a simple mechanism the MKB key which is found in the physical support of the disc follows a complex structure. The MKB is distributed in blocks that contain the version of the Media key, the list of devices that have been revoked, a field to authenticate the MKB, and other fields that specify parameters corresponding to the decrypting algorithm and define the structure of the own Media Key and also the Media key itself.
The MKB itself is found inside the field Media Key Data Record and has a variable length but it is always a multiple of 4 bytes.
This situation has become even worse with the recent publication in multiple web sites of the Media Key, that is, the key that allows decrypting the Volume ID
, and at the same time, the encrypted content, without the need of using a certified device by the AACS or a valid MKB. This is especially critical because nowadays the Volume ID is the same in all the Blu-ray or HD-DVDs with equal content.
Digital rights management
Digital rights management is a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals with the intent to limit the use of digital content and devices after sale. DRM is any technology that inhibits uses of digital content that...
) AACS
Advanced Access Content System
The Advanced Access Content System is a standard for content distribution and digital rights management, intended to restrict access to and copying of the "next generation" of optical discs and DVDs. The specification was publicly released in April 2005 and the standard has been adopted as the...
. This system is used to protect Blu-ray and HD DVD
HD DVD
HD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format...
formats from being copied. The system has been developed by big companies from the film industry and the electronics industry like: IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
, Intel, Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
, Matsushita (Panasonic), Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
, Toshiba
Toshiba
is a multinational electronics and electrical equipment corporation headquartered in Tokyo, Japan. It is a diversified manufacturer and marketer of electrical products, spanning information & communications equipment and systems, Internet-based solutions and services, electronic components and...
, The Walt Disney Company
The Walt Disney Company
The Walt Disney Company is the largest media conglomerate in the world in terms of revenue. Founded on October 16, 1923, by Walt and Roy Disney as the Disney Brothers Cartoon Studio, Walt Disney Productions established itself as a leader in the American animation industry before diversifying into...
and Warner Bros.
Warner Bros.
Warner Bros. Entertainment, Inc., also known as Warner Bros. Pictures or simply Warner Bros. , is an American producer of film and television entertainment.One of the major film studios, it is a subsidiary of Time Warner, with its headquarters in Burbank,...
.
The MKB key is found in the physical support (the disc) together with the content of the disc encrypted. The MKB has the function of validating the reproduction devices on which the disc is being played and obtaining, from the devices codes, the key that will allow the decryption of the disc content. That is the Media key (Km).
How it works
Blu-Ray or HD-DVD have as content the encrypted data (usually video), the Volume ID (VID), the Encrypted Title KeyEncrypted Title Key
Encrypted Title Key is an encrypted key that belongs to anticopy Advanced Access Content System . This key is included in the Media Key Block system and is an important part of the content protection process of Blu-ray and HD-DVD contents....
(s) and the MKB. The MKB is also found encrypted in the disc to prevent it from being extracted off the disc and being manipulated and/or reproduced by another non authorized device.
Device Keys
Device Keys play a role in the cryptographic key management procedure in the Advanced Access Content System specification. This specification defines a method for protecting audiovisual entertainment content, including high-definition content....
. These keys are conceded by the AACS organization. In the moment of the reproduction, one of these keys will decrypt the MKB contained on the disc and as a result of this process we obtain the Media key.
The Media key is combined together with the VID (Volume ID) and as a result we obtain the Volume Unique Key (Kvu). With the Kvu we are able to decrypt the Encrypted Title Key and obtain the Title keys which finally allows to decrypt the content of the disc and view it.
This way the system can protect contents from being viewed in devices that have not been authorized. Therefore, the system allows modifying the MKB in future relaunch of a determined content in order to select the devices in which this content can be viewed.
Key Structure
The MKB itself is found inside the field Media Key Data Record and has a variable length but it is always a multiple of 4 bytes.
Advantages and disadvantages
Many consumers associations have complained against this protection system since it can lead to a situation where physical devices cannot reproduce contents even though they do not infringe any intellectual property. This situation can be achieved either by trying to reproduce some content in old devices, therefore not certified by the AACS, or because the device model has been disallowed by AACS, as a result all the owners of that device model will not be able to view contents protected with the MKB.This situation has become even worse with the recent publication in multiple web sites of the Media Key, that is, the key that allows decrypting the Volume ID
, and at the same time, the encrypted content, without the need of using a certified device by the AACS or a valid MKB. This is especially critical because nowadays the Volume ID is the same in all the Blu-ray or HD-DVDs with equal content.