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{{short description|Standard for content distribution and digital rights management}}
{{current}}
{{Update|date=August 2017}}
The '''Advanced Access Content System''' ('''AACS''') is a ] for ] and ], intended to allow restricting access to and ] of the next ] of optical discs and ]s. The specification was publicly released in April 2005 and the standard has been adopted as the access restriction scheme for ] and ] (BD). The group developing it includes ], ], ], ] (Panasonic), ], ], ], and ].
{{Use dmy dates|date=February 2020}}
]
The '''Advanced Access Content System''' ('''AACS''') is a ] for ] and ], intended to restrict access to and copying of the post-] generation of optical discs. The specification was publicly released in April 2005. The standard has been adopted as the access restriction scheme for ] and ] (BD). It is developed by ] (AACS LA), a ] that includes ], ], ], ], ], ], ] and ]. AACS has been operating under an "interim agreement" since the final specification (including provisions for ]) has not yet been finalized.


Since appearing in devices in 2006, several successful attacks have been made on the format. The first known attack relied on the ] problem, and the decryption keys for a volume were able to be extracted from a weakly protected player (]). A more recent and so far unconfirmed attack claims to have spotted one of the required keys on the disks themselves. Since appearing in devices in 2006, several AACS decryption keys have been extracted from software players and published on the Internet, allowing decryption by unlicensed software.


==System overview== ==System overview==
===Encryption===
AACS uses ] to control the use of digital media. AACS-protected content is encrypted under one or more ''title keys'' using the ] (AES). Title keys are derived from a combination of a ''media key'' and several elements, including the ''volume ID'' of the media (e.g., a physical serial number embedded on a DVD), and a ] of the title ''usage rules''.
AACS uses ] to control and restrict the use of digital media. It encrypts content under one or more ''title keys'' using the ] (AES). Title keys are decrypted using a combination of a ''media key'' (encoded in a ]) and the ''Volume ID'' of the media (e.g., a physical serial number embedded on a pre-recorded disc).


The principal difference between AACS and earlier content management systems such as ] is in the means by which title-specific decryption keys are distributed. Under ], all players of a given model are provisioned with the same, shared decryption key. Content is encrypted under the title-specific key, which is itself encrypted under each model's key. The principal difference between AACS and ] (the DRM system used on DVDs) lies in how the device decryption keys and codes are organized.


Under CSS, all players of a given model group are provisioned with the same shared activated decryption key. Content is encrypted under the title-specific key, which is itself encrypted under each model's key. Thus each disc contains a collection of several hundred encrypted keys, one for each licensed player model.
In CSS, each volume contains a collection of several hundred encrypted keys, one for each licensed player model. In principle, this approach allows licensors to "revoke" a given player model (prevent it from playing back future content) by omitting the encryption key corresponding to that model. In practice, however, revoking all players of a particular model is costly, as it causes many users to lose playback capability. Furthermore, the inclusion of a shared key across many players makes key compromise significantly more likely, as was demonstrated by a number of compromises in the mid-1990s.


In principle, this approach allows licensors to "revoke" a given player model (prevent it from playing back future content) by omitting to encrypt future title keys with the player model's key. In practice, however, revoking all players of a particular model is costly, as it causes many users to lose playback capability. Furthermore, the inclusion of a shared key across many players makes key compromise significantly more likely, as was demonstrated by a number of compromises in the mid-1990s.
The approach of AACS provisions each individual player with a unique set of decryption keys which are used in a ] scheme. This approach allows licensors to "revoke" individual players, or more specifically, the decryption keys associated with the player. Thus, if a given player's keys are compromised and published by an attacker, the AACS licensing authority can simply revoke those keys in future content, making the keys/player useless for decrypting new titles. However, if the attacker doesn't publish the compromised player key, the AACS licensing authority doesn't know which key is compromised, and it can not revoke it. An attacker can use his/her player key to get title keys of several movies, and publish the title keys or the decrypted movies, without risk of revocation of his/her player key.


The approach of AACS provisions each individual player with a unique set of decryption keys which are used in a ] scheme. This approach allows licensors to "revoke" individual players, or more specifically, the decryption keys associated with the player. Thus, if a given player's keys are compromised and published, the AACS LA can simply revoke those keys in future content, making the keys/player useless for decrypting new titles.
==Security of AACS==


AACS also incorporates ] techniques. The standard allows for multiple versions of short sections of a movie to be encrypted with different keys, while a given player will only be able to decrypt one version of each section. The manufacturer embeds varying ] (such as ]) in these sections, and upon subsequent analysis of the pirated release the compromised keys can be identified and revoked (this feature is called ''Sequence keys'' in the AACS specifications).<ref>{{cite web
{{Cleanup-section|February 2007}}
| author = Hongxia Jin |author2=Jeffery Lotspiech |author3-link=Nimrod Megiddo |author3=Nimrod Megiddo
| title = Efficient Traitor Tracing
|date=4 October 2006
| url = http://domino.watson.ibm.com/library/cyberdig.nsf/papers/AF8C220CB33D5A98852571FF00570458/$File/rj10390.pdf
| access-date = 2 May 2007}}</ref><ref>{{cite web
|title = AACS Reference: Pre-recorded Video Book
|url = http://www.aacsla.com/specifications/specs091/AACS_Spec_Prerecorded_0.91.pdf
|access-date = 2 May 2007
|archive-url = https://web.archive.org/web/20120206054929/http://www.aacsla.com/specifications/specs091/AACS_Spec_Prerecorded_0.91.pdf
|archive-date = 6 February 2012
|url-status = dead
|df = dmy-all
}}</ref>


===Concerns of experts=== === Volume IDs ===
Volume IDs are unique identifiers or ]s that are stored on pre-recorded discs with special hardware. They cannot be 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 ].<ref>{{cite web |url=http://www.aacsla.com/specifications/AACS_Spec_BD_Prerecorded_0.912.pdf |title=Blu-ray Disc Pre-recorded Book |access-date=1 November 2007 |date=27 July 2006 |publisher=AACS LA |page=15 |archive-url=https://web.archive.org/web/20071106065659/http://www.aacsla.com/specifications/AACS_Spec_BD_Prerecorded_0.912.pdf |archive-date=6 November 2007 |url-status=dead}}</ref>
The proposal was voted one of the technologies most likely to fail by '']'' magazine's readers in the January 2005 issue . Concerns about the approach include its similarity to past systems that failed, such as ] (CSS), and the inability to preserve security against attacks that compromise large numbers of players. ] ("DVD Jon"), who defeated the original DVD CSS, expected AACS to be cracked by winter 2006/2007 .


To read the Volume ID, a cryptographic ] (the ''Private Host Key'') signed by the AACS LA is required. However, this has been circumvented by modifying the firmware of some HD DVD and Blu-ray drives.<ref name=arstechnica-aacs>{{cite web
In late 2006, security expert ] released , a technical paper criticizing the implementation of AACS on ]. <blockquote>
|url=https://arstechnica.com/news.ars/post/20070415-aacs-cracks-cannot-be-revoked-says-hacker.html
Providing this protection incurs considerable costs in terms of system performance, system stability, technical support overhead, and hardware and software cost. These issues affect not only users of Vista but the entire PC industry, since the effects of the protection measures extend to cover all hardware and software that will ever come into contact with Vista, even if it's not used directly with Vista (for example hardware in a Macintosh computer or on a Linux server).
|title=New AACS cracks cannot be revoked, says hacker.
</blockquote>
|access-date=4 May 2007
|first=Jeremy
|last=Reimer
|date=15 April 2007
|work=Ars Technica
|archive-url=https://web.archive.org/web/20070504171556/http://arstechnica.com/news.ars/post/20070415-aacs-cracks-cannot-be-revoked-says-hacker.html
|archive-date=4 May 2007
|url-status=live
}}</ref><ref>{{cite web
|url = http://forum.doom9.org/showthread.php?t=124294
|title = Got VolumeID without AACS authentication :)
|access-date = 4 May 2007
|author = Geremia
|date=4 April 2007
|work=Doom9.net forums| archive-url= https://web.archive.org/web/20070510023247/http://forum.doom9.org/showthread.php?t=124294| archive-date= 10 May 2007 | url-status= live}}</ref>


===Initial steps=== === Decryption process ===
To view the movie, the player must first decrypt the content on the disc. The decryption process is somewhat convoluted. The disc contains 4 items—the Media Key Block (MKB), the Volume ID, the Encrypted Title Keys, and the Encrypted Content. The MKB is encrypted in a subset difference tree approach. Essentially, a set of keys are arranged in a tree such that any given key can be used to find every other key except its parent keys. This way, to revoke a given ], the MKB needs only be encrypted with that device key's parent key.
In July ], the first steps towards enabling full AACS-encrypted films to be copied were taken. While great care has been taken with AACS to ensure that contents are encrypted right up to the display device, it was discovered that a perfect copy of any still frame from a film could be captured from certain ] and ] software players made simply by utilizing the ] function of the Windows operating system. It was hypothesized that this approach could be automated to allow a perfect copy of an entire film to be made, in much the same way that DVD films were copied before the advent of ], but to date no such copy has been discovered, and this exploit has been closed in subsequent software versions.


Once the MKB is decrypted, it provides the Media Key, or the ''km''. The ''km'' is combined with the Volume ID (which the program can only get by presenting a cryptographic certificate to the drive, as described above) in a one-way encryption scheme (AES-G) to produce the Volume Unique Key (''Kvu''). The ''Kvu'' is used to decrypt the encrypted title keys, and that is used to decrypt the encrypted content.<ref name=arstechnica-aacs /><ref>{{cite web
Such approaches do not constitute compromises of the AACS encryption itself, relying instead on an officially licensed software player to perform the decryption. As such, the output data will not be in the form of the compressed video from the disc, but rather decompressed video.
|url = http://www.aacsla.com/specifications/specs091/AACS_Spec_Common_0.91.pdf
|title = Advanced Access Content System (AACS): Introduction and Common Cryptographic Elements
|access-date = 5 June 2007
|date = 17 February 2007
|work = AACS Licensing Administrator
|archive-url = https://web.archive.org/web/20070302130221/http://www.aacsla.com/specifications/specs091/AACS_Spec_Common_0.91.pdf
|archive-date = 2 March 2007
|url-status = dead
|df = dmy-all
}}</ref>


=== Analog Outputs ===
===Muslix64's exploit and BackupHDDVD / BackupBluRay===
{{update|'''--This needs to be updated so it doesn't deal mostly with the obsolete HD-DVD format--'''|date=November 2010}}
On ] ] a person using the alias "muslix64" a utility named ] and its source code for a working AACS decryptor on the forums.
The program is not an exploit or hack per se. Rather it is a tool that can be used to decrypt AACS protected content once one knows the encryption key. As such, it is no surprise or indication of vulnerability that such a program is possible and it can be seen as merely an implementation of the publicly available standard .
However, Muslix64 claims to have found title keys in main memory while playing HD-DVD disks using a software player, and that finding them is not difficult<ref>{{cite web | date=] | url=http://www.techamok.com/?pid=1849 | title=HD-DVD Content Protection already hacked? | work=] | accessdate=2007-01-02 }}</ref>. Details of how to do this were later revealed<ref>{{cite web | date=] | url=http://forum.doom9.org/showthread.php?t=119871&page=33 | title=How to extract HD-DVD title keys from WinDVD's memory | accessdate=2007-01-19}}</ref>.


{{main|Image Constraint Token}}
On ] ] "muslix64" published a new version of his/her program, with volume key support.
AACS-compliant players must follow guidelines pertaining to outputs over analog connections. This is set by a flag called the Image Constraint Token (ICT), which restricts the resolution for analog outputs to 960×540. Full 1920×1080 resolution is restricted to HDMI or DVI outputs that support ]. The decision to set the flag to restrict output ("down-convert") is left to the content provider. Warner Pictures is a proponent of ICT, and it is expected that Paramount and Universal will implement down-conversion as well.<ref>{{cite web|url=http://www.videobusiness.com/article/CA6300812.html |title=High-def 'down-converting' forced |access-date=4 May 2007 |date=19 January 2006 |last=Sweeting |first=Paul |work=Video Business |url-status=dead |archive-url=https://web.archive.org/web/20060415091053/http://www.videobusiness.com/article/CA6300812.html |archive-date=15 April 2006 }}</ref>
AACS guidelines require that any title which implements the ICT must clearly state so on the packaging. The German magazine "Der Spiegel" has reported about an unofficial agreement between film studios and electronics manufacturers to not use ICT until 2010 – 2012.<ref>{{cite web |url=https://arstechnica.com/news.ars/post/20060521-6880.html |title=Hollywood reportedly in agreement to delay forced quality downgrades for Blu-ray, HD DVD |access-date=2 November 2007 |author =Ken Fisher |date=21 May 2006 |work=arstechnica.com| archive-url= https://web.archive.org/web/20071105063630/http://arstechnica.com/news.ars/post/20060521-6880.html| archive-date= 5 November 2007 | url-status= live}}</ref> However, some titles have already been released that apply ICT.<ref>{{cite web|url=http://www.areadvd.de/news/2007/200710/29102007001_RE_HD_DVD.shtml |title=HD DVD: "Resident Evil" nur in Standard-Auflösung via YUV |access-date=2 November 2007 |date=29 October 2007 |work=areadvd.de |language=de |url-status=dead |archive-url=https://web.archive.org/web/20080111071532/http://www.areadvd.de/news/2007/200710/29102007001_RE_HD_DVD.shtml |archive-date=11 January 2008 }}</ref>


=== Audio watermarking ===
], developers of ] maintain that their software was not used as part of the exploit. However, it has been claimed that their key is used by ] and later the user "jx6bpm" on 's forums revealed ]'s ]'s key to be 4737676058d7029452514f0ab186dc4cca8c578f.
On 5 June 2009, the licensing agreements for AACS were finalized, which were updated to make ] detection on commercial Blu-ray disc players a requirement.<ref>{{Cite press release | title = AACS Issues Final Agreements, Enabling Commercial Deployment of Cinavia in Blu-ray Disc Players | publisher = Verance | date = 5 June 2009 | url = http://www.verance.com/AdminSavR/news/news_item.php?news_id=42 | access-date = 11 October 2010 | archive-url = https://web.archive.org/web/20091009025320/http://www.verance.com/AdminSavR/news/news_item.php?news_id=42 | archive-date = 9 October 2009 | url-status = dead | df = dmy-all }}</ref>


===Managed Copy===
The claimed attack (extraction of the encryption keys from a software player) highlights the inherent weakness of software movie players for the PC platform. The use of encryption doesn't offer any true protection in this scenario since the software player must have the encryption key available somewhere in memory and there's no way to protect against a determined hacker extracting the encryption key (if everything else fails the user could run the program in a ] making it possible to freeze the program and inspect all memory addresses without the program knowing). Avoiding such attacks would require changes to the PC platform (see ]) or that the content distributors do not permit their content to be played on PCs at all (by not providing the companies making software players with the needed encryption keys). Alternatively, they could use the AACS system's revocation mechanism to revoke a specific software player after it is known to have been compromised. In that case, the compromised players could still be used to break old titles but not newer releases as they would be released without encryption keys for the compromised software players requiring hackers to break other players. The latter alternative is not a desirable option, because it would result in legitimate users of compromised players being forced to upgrade or replace their player software in order to view new titles.
'''Managed Copy''' refers to a system by which consumers can make legal copies of films and other digital content protected by AACS. This requires the device to obtain authorization by contacting a remote server on the Internet. The copies will still be protected by ], so infinite copying is not possible (unless it is explicitly allowed by the content owner). It is mandatory for content providers to give the consumer this flexibility in both the HD DVD and the Blu-ray standards (commonly called ''Mandatory Managed Copy''). The Blu-ray standards adopted Mandatory Managed Copy later than HD DVD, after ] requested it.<ref>{{cite web
| date = 5 February 2006
| url = http://www.hp.com/hpinfo/newsroom/press/2005/051216a.html
| title =HP to Support HD-DVD High-definition DVD Format and Join HD-DVD Promotions Group
| access-date = 3 May 2007
| archive-url= https://web.archive.org/web/20070504142655/http://www.hp.com/hpinfo/newsroom/press/2005/051216a.html| archive-date= 4 May 2007 | url-status= live}}</ref>


Possible scenarios for Managed Copy include (but are not limited to):
On ] ] "LordSloth" on Doom9 discovered how to grab the volume license keys from WinDVD's memory. With that discovery, it became possible to take backup of HD DVDs. Later that day, the first pirated HD DVD, '']'', was uploaded on a private torrent tracker. That marked the start of HD DVD piracy.


* Create an exact duplicate onto a recordable disc for backup
On ] ] "muslix64" published the alpha version of ].
* Create a full-resolution copy for storage on a media server
* Create a scaled-down version for watching on a portable device


This feature was not included in the interim standard, so the first devices on the market did not have this capability.<ref name=pcworld-burning-questions>{{cite web
===Publishing of Volume Keys===
| url = http://www.pcworld.com/article/id,124961-page,1/article.html
In addition, on ] ] a website launched at containing a complete database of all known HD DVD volume keys, and a of the BackupHDDVD software allowing for online key retrieval.
| title = Burning Questions: No Copying From First High-Def Players
| first = Melissa J.
| last = Perenson
| date = 21 March 2006
| work = PC World
| access-date = 5 May 2007
| archive-date = 9 October 2007
| archive-url = https://web.archive.org/web/20071009194043/http://www.pcworld.com/article/id,124961-page,1/article.html
| url-status = dead
}}</ref> It was expected to be a part of the final AACS specification.<ref>{{Cite web
|url= https://arstechnica.com/gadgets/news/2007/05/hd-dvd-blu-ray-managed-copy-coming-later-this-year.ars
|title=HD DVD, Blu-ray "Managed Copy" coming later this year
|work=arstechnica.com
|date=24 May 2007
|access-date=29 June 2010
| archive-url= https://web.archive.org/web/20100526040122/http://arstechnica.com/gadgets/news/2007/05/hd-dvd-blu-ray-managed-copy-coming-later-this-year.ars| archive-date= 26 May 2010 | url-status= live}}</ref>


In June 2009, the final AACS agreements were ratified and posted online, and include information on the Managed Copy aspects of AACS.
On January 26, 2007 the ] reported "The AACS group has admitted that a hacker had managed to decrypt some discs and other people were now able to make copies of certain titles." In a recent interview muslix64 said the reason he hacked the AACS was he got angry when a HD-DVD he bought wouldn't play on his monitor because it didn't have the compliant connector. He says "Not being able to play a movie that I have paid for, because some executive in Hollywood decided I cannot, made me mad." Muslix64 also said "I'm just an upset customer. My efforts can be called '] enforcement'."


===AnyDVD HD=== == History ==


On 24 February 2001, Dalit Naor, Moni Naor and Jeff Lotspiech published a paper entitled "Revocation and Tracing Schemes for Stateless Receivers", where they described a broadcast encryption scheme using a construct called Naor-Naor-Lotspiech subset-difference trees. That paper laid the theoretical foundations of AACS.<ref>{{cite web|url=http://www.playfuls.com/news_05648_HD_DVDs_AACS_Protection_Bypassed_In_Only_8_Days.html |title=HD DVD's AACS Protection Bypassed. In Only 8 Days?! |access-date=25 October 2007 |author=Dan Nicolae Alexa |date=28 December 2006 |work=playfuls.com |url-status=dead |archive-url=https://web.archive.org/web/20080210005229/http://www.playfuls.com/news_05648_HD_DVDs_AACS_Protection_Bypassed_In_Only_8_Days.html |archive-date=10 February 2008 }}</ref>
] have released ] HD which allows users to watch HD-DVD (and Blu-Ray in the current beta versions) movies on non-HDCP compliant PC hardware. The movies can be decrypted on the fly direct from the HD-DVD or can be copied to harddisk. AnyDVD HD also automatically removes any unwanted logos and trailers. They have stated that AnyDVD HD uses several different mechanisms to disable the encryption, and is not dependent on the use of compromised encryption keys. They have also stated that AACS has even more flaws in its implementation than CSS, rendering it highly vulnerable, but they will release no details for obvious reasons. Users at Doom9 that the program makes use of the host certificate of ] version 6.5, but SlySoft has that the program would be unaffected by the AACS revocation system.


The AACS LA consortium was founded in 2004.<ref>{{cite magazine |url=http://archive.wired.com/entertainment/music/news/2004/07/64212 |title=Can Odd Alliance Beat Pirates? |access-date=20 January 2015 |author =Katie Dean |date=15 July 2004 |magazine=Wired }}</ref> With ] in hindsight, the '']'' magazine's readers voted AACS to be one of the technologies most likely to fail in the January 2005 issue.<ref>{{cite web
===Processing key retrieval and Arnezami contribution===
|url = http://www.spectrum.ieee.org/jan05/2703
A person known as Arnezami on the doom9 forums posted a processing key for AACS on 11 February 2007. This key is suitable to decrypt any HD-DVD or BluRay disc published to date. With the help of this key it is possible to generate a VUK (Volume Unique Key) for any disc. However, this requires knowledge
|title = Loser: DVD Copy Protection, Take 2
of the Volume ID for each particular release.
|access-date = 4 May 2007
|author = Tekla S. Perry
|date = January 2007
|work = Spectrum Online
|archive-url = https://web.archive.org/web/20070608074811/http://spectrum.ieee.org/jan05/2703
|archive-date = 8 June 2007
|url-status = dead
}}</ref>
The final AACS standard was delayed,<ref>{{cite web|url=http://www.pcworld.com/article/id,123924-page,1/article.html |title=Toshiba Hints at HD-DVD Delay |access-date=19 October 2007 |author=Martyn Williams |date=14 December 2005 |work=pcworld.com |archive-url=https://web.archive.org/web/20071005171717/http://www.pcworld.com/article/id%2C123924-page%2C1/article.html |archive-date=5 October 2007 |url-status=live }}</ref> and then delayed again when an important member of the Blu-ray group voiced concerns.<ref>{{cite web |url=http://www.heise.de/english/newsticker/news/69559 |title=AACS copy protection for Blu-ray disc and HD DVD delayed again |access-date=19 October 2007 |author =Craig Morris |date=14 February 2006 |work=heise.de | archive-url= https://web.archive.org/web/20071102222432/http://www.heise.de/english/newsticker/news/69559| archive-date= 2 November 2007 | url-status= live}}</ref> At the request of Toshiba, an interim standard was published which did not include some features, like managed copy.<ref name=pcworld-burning-questions /> On July 5, 2009 the license of AACS1 went online.<ref>{{Cite web |last=Calonge |first=Juan |date=8 June 2009 |title=AACS Final License Goes Online |url=https://www.blu-ray.com/news/?id=2849 |access-date=11 March 2023 |website=blu-ray.com}}</ref>


==Unlicensed decryption==
The Volume ID structure has four fields, one byte which designates the MediaType (always equal to 0x40), one byte which is reserved (always zero so far), an array of 12 bytes (so-called "unique number" assigned by publisher), and two bytes which are reserved (again always zero so far).
On 26 December 2006, a person using the ] "muslix64" published a working, open-sourced AACS decrypting utility named ], looking at the publicly available AACS specifications. Given the correct keys, it can be used to decrypt AACS-encrypted content. A corresponding BackupBluRay program was soon developed.<ref>{{cite web
| url = https://www.engadget.com/2007/01/24/backupbluray-available-now-too/
| first = Ben
| last = Drawbaugh
| title = BackupBluray available now too
| access-date = 3 May 2007
|date=24 January 2007
| work = Engadget| archive-url= https://web.archive.org/web/20070516060453/http://www.engadget.com/2007/01/24/backupbluray-available-now-too/| archive-date= 16 May 2007 | url-status= live}}</ref> Blu-ray Copy is a program capable of copying Blu-rays to the ] or to blank BD-R discs.<ref>{{cite news|title=Get Blu-ray Copy (Win) for free|url=http://reviews.cnet.com/8301-33153_7-57468788-10391733/get-blu-ray-copy-win-for-free/|first=Rick|last=Broida|date=9 July 2012|work=]|access-date=18 July 2013}}</ref>


==Security==
At the moment known IDs could be easily guessed or brute-forced. Arnezami found out that the "unique" part of the ID on currently available releases is not randomly generated as it was originally anticipated. Actual values for the "unique" part of a Volume ID (the "unique number" in this structure is 12 bytes long) can be the date/time of release, part of the movie title in plain text (e.g. "SERENITY "), and so on.
{{Main|Security of Advanced Access Content System}}


Both title keys and one of the keys used to decrypt them (known as ''Processing Keys'' in the AACS specifications) have been found by using debuggers to inspect the memory space of running HD DVD and Blu-ray player programs.<ref>{{cite web
Although Arnezami made a great advance, a fully automated solution for decrypting HD-DVD/BluRay is yet to be implemented with this approach. Publishers might introduce randomly generated Volume IDs in future releases (brute-forcing 12 bytes key is practically
| url = http://www.techamok.com/?pid=1849
impossible on current systems). However, due to the specific structure of the volume id it is feasible to do an automated search
| title = HD-DVD Content Protection already hacked?
of such a structure in a software player's memory (even if there are many - possibly thousands - of candidates, it is easy to find the VUK with a brute-force implementation).
| work = TechAmok
|date=28 December 2006
| access-date = 2 January 2007 }}</ref><ref>{{cite news
| url = http://news.bbc.co.uk/2/hi/technology/6301301.stm
| title = Hi-def DVD security is bypassed
|date=26 January 2007
|access-date=2 May 2007
|work=BBC News| archive-url= https://web.archive.org/web/20070505121314/http://news.bbc.co.uk/2/hi/technology/6301301.stm| archive-date= 5 May 2007 | url-status= live}}</ref><ref>{{cite web
| last = Block
| first = Ryan
| url = https://www.engadget.com/2007/01/20/blu-ray-cracked-too/
| title = Blu-ray cracked too?
|date=20 January 2007
| access-date = 22 January 2007
|work=Engadget | archive-url= https://web.archive.org/web/20070123114257/http://www.engadget.com/2007/01/20/blu-ray-cracked-too/| archive-date= 23 January 2007 | url-status= live}}</ref><ref>{{cite web
| url = https://www.theregister.co.uk/2007/01/23/blu-ray_drm_cracked/
| first = John
| last = Leyden
| work = The Register
| title = Blu-ray DRM defeated
|date=23 January 2007
| access-date = 22 January 2007| archive-url= https://web.archive.org/web/20070125175901/https://www.theregister.co.uk/2007/01/23/blu-ray_drm_cracked/| archive-date= 25 January 2007 | url-status= live}}</ref>
Hackers also claim to have found Device Keys<ref>{{cite web
|url=http://forum.doom9.org/showthread.php?t=122664
|title=WinDVD 8 Device Key Found!
|access-date=4 May 2007
|author =ATARI Vampire
|date=24 February 2007
|work=Doom9.net forums}}</ref>
(used to calculate the Processing Key) and a Host Private Key<ref>{{cite web
|url=http://forum.doom9.org/showthread.php?t=122969
|title=PowerDVD private key
|access-date=4 May 2007
|author =jx6bpm
|date=3 March 2007
|work=Doom9.net forums| archive-url= https://web.archive.org/web/20070329033807/http://forum.doom9.org/showthread.php?t=122969| archive-date= 29 March 2007 | url-status= live}}</ref>
(a key signed by the AACS LA used for hand-shaking between host and HD drive; required for reading the Volume ID). The first unprotected HD movies were available soon afterwards.<ref>
{{cite web
|url=http://www.dailytech.com/article.aspx?newsid=5747
|title=First Pirated HD DVDs Released
|access-date=3 May 2007
|first=Marcus
|last=Yam
|date=17 January 2007
|work=DailyTech
|archive-url=https://web.archive.org/web/20070219103102/http://www.dailytech.com/article.aspx?newsid=5747
|archive-date=19 February 2007
|url-status=dead
}}
</ref>
The ] on the Internet after it was found and the AACS LA sent multiple ]s in the aim of censoring it.<ref>{{cite web
|url=http://www.chillingeffects.org/notice.cgi?sID=3218
|title=AACS licensor complains of posted key
|access-date=2 May 2007}}</ref>
Some sites that rely on user-submitted content, like ] and Misplaced Pages, tried to remove any mentions of the key.<ref>{{cite magazine
|url=http://blog.wired.com/business/2007/05/wikipedia_locks.html
|title=Misplaced Pages Locks Out "The Number"
|last=Boutin
|access-date=2 May 2007
|date=1 May 2007
|magazine=Wired| archive-url= https://web.archive.org/web/20070504012402/http://blog.wired.com/business/2007/05/wikipedia_locks.html| archive-date= 4 May 2007 | url-status= live}}</ref><ref>{{cite news
|title=Digg's DRM Revolt
|first=Andy
|last=Greenberg
|date=2 May 2007
|work=Forbes
|url=https://www.forbes.com/technology/2007/05/02/digital-rights-management-tech-cx_ag_0502digg.html
|access-date=4 May 2007| archive-url= https://web.archive.org/web/20070504173353/http://www.forbes.com/technology/2007/05/02/digital-rights-management-tech-cx_ag_0502digg.html| archive-date= 4 May 2007 | url-status= dead}}</ref>
The Digg administrators eventually gave up trying to censor submissions that contained the key.<ref>{{cite news
|url=http://news.bbc.co.uk/2/hi/technology/6615047.stm
|title=DVD DRM row sparks user rebellion
|access-date = 2 May 2007
|date=2 May 2007
|work=BBC News| archive-url= https://web.archive.org/web/20070516215800/http://news.bbc.co.uk/2/hi/technology/6615047.stm| archive-date= 16 May 2007 | url-status= live}}</ref>


The AACS key extractions highlight the inherent weakness in any DRM system that permit software players for PCs to be used for playback of content. No matter how many layers of encryption are employed, it does not offer any true protection, since the keys needed to obtain the unencrypted content stream must be available somewhere in memory for playback to be possible. The PC platform offers no way to prevent memory snooping attacks on such keys, since a PC configuration can always be emulated by a ], in theory without any running program or external system being able to detect the virtualization. The only way to wholly prevent attacks like this would require changes to the PC platform (see ]) which could provide protection against such attacks. This would require that content distributors do not permit their content to be played on PCs without trusted computing technology, by not providing the companies making software players for non-trusted PCs with the needed encryption keys.
Remarkably, Arnezami didn't dissassemble or even debug software player code and used a different technique to the one employed by muslix64. Volume IDs were intercepted by a USB sniffer only and the processing key was found in a memory dump taken at the appropriate moment (after VUK generation, the software player was found to erase the processing key from RAM). This hack was carried out using WinDVD and an XBox 360 HD-DVD drive, connected to a PC using its existing USB connection. This discovery is another major fault in the current AACS implementation (sending the Volume ID unencrypted from an HD-DVD reading device over an unprotected channel to a software player).


On 16 April 2007, the AACS consortium announced that it had expired certain encryption keys used by PC-based applications. Patches were available for WinDVD and PowerDVD which used new and uncompromised encryption keys.<ref>
===Legal agreements===
{{cite web| url= http://www.aacsla.com/press/| title= Press Messages: AACS – Advanced Access Content System| access-date= 2 May 2007| archive-url= https://web.archive.org/web/20070430070403/http://www.aacsla.com/press/| archive-date= 30 April 2007| url-status= dead| df= dmy-all}}
The AACS web site notes that text for Final agreements regarding AACS licensing will be replacing the Interim agreements on ] ]. This applies to the Adopter Agreement, Content Participant Agreement, Content Provider Agreement, Reseller agreement.
</ref><ref>
:"Please note that, in anticipation of the Final AACS Content Participant Agreement being available, this Interim AACS Content Participant Agreement will no longer be available for download or execution after January 31, 2007, and the AACS LA will not accept submissions of this document after that date. Thank you for your understanding as AACS LA progresses toward offering the final license agreements.
{{cite web
|url=http://dailytech.com/AACS+Responds+to+Cracked+HD+DVD+and+Bluray+Disc+Protections/article5879.htm
|title=AACS Responds to Cracked HD DVD and Blu-ray Disc Protections
|access-date=3 May 2007
|first=Marcus
|last=Yam
|date=26 January 2007
|work=DailyTech
|archive-url=https://web.archive.org/web/20070211005800/http://dailytech.com/AACS+Responds+to+Cracked+HD+DVD+and+Bluray+Disc+Protections/article5879.htm
|archive-date=11 February 2007
|url-status=dead
}}
</ref>
The old, compromised keys can still be used to decrypt old titles, but not newer releases as they will be encrypted with these new keys. All users of the affected players (even those considered "legitimate" by the AACS LA) are forced to upgrade or replace their player software in order to view new titles.


Despite all revocations, current titles can be decrypted using new MKB v7, v9 or v10 keys widely available in the Internet.
===Hardware products===

AACS is implemented within drive. Accompanying the drive is also . It is unclear whether Plextor and/or WinDVD/Ulead software (included with the drive) is initiating and perhaps profiting from this charge, or if this is required by licensing AACS into product capabilities. Some argue it is grossly inappropriate that after you purchase a $900+ piece of hardware, that sometime in the future you would need to purchase a key to play back new Blu-ray Movies. This usage restriction is not indicated on the outside of the container, you must open it in order to discover it.
Besides spreading ''processing keys'' on the Internet, there have also been efforts to spread ''title keys'' on various sites.<ref>
{{cite web
|url=http://www.newsfactor.com/news/Blu-ray--HD-DVD-Encryption-Cracked/story.xhtml?story_id=121000E3UUOA
|title=Blu-ray and HD DVD Encryption Cracked
|access-date=29 May 2007
|author=Lindsay Martell
|date=26 January 2007
|work=NewsFactor Network
|archive-url=https://web.archive.org/web/20071103050531/http://www.newsfactor.com/news/Blu-ray--HD-DVD-Encryption-Cracked/story.xhtml?story_id=121000E3UUOA
|archive-date=3 November 2007
|url-status=dead
}}
</ref>
The AACS LA has sent ]s to such sites on at least one occasion.<ref>
{{cite web
|url=http://forum.doom9.org/attachment.php?attachmentid=7071&d=1176327932
|title=Illegal Offering of Title/Volume Keys to Circumvent AACS Copyright Protection: hdkeys.com
|format=pdf
|access-date=29 May 2007
|author =Alexander Kaplan
|date=5 April 2007
|work=DMCA takedown notice
}}</ref>
There is also commercial software (]) that can circumvent the AACS protection. Apparently this program works even with movies released after the AACS LA expired the first batch of keys.<ref>
{{cite web
|url=https://arstechnica.com/news.ars/post/20070517-latest-aacs-revision-defeated-a-week-before-release.html
|title=Latest AACS revision defeated a week before release
|access-date=29 May 2007
|author =Ryan Paul
|date=7 May 2007
|work=Ars Technica
| archive-url= https://web.archive.org/web/20070520054415/http://arstechnica.com/news.ars/post/20070517-latest-aacs-revision-defeated-a-week-before-release.html| archive-date= 20 May 2007 | url-status= live}}
</ref>

While great care has been taken with AACS to ensure that contents are encrypted right up to the display device, on the first versions of some ] and ] software players a perfect copy of any still frame from a film could be made simply by utilizing the ] function of the Windows operating system.<ref>{{cite web
| url = http://hardware.slashdot.org/article.pl?sid=06/07/07/1255224
| title = Work Around for New DVD Format Protections
|date=7 June 2006
| access-date = 2 May 2007
| work = ]}}</ref><ref>{{cite web
| url = http://www.heise-online.co.uk/security/Copy-protection-hole-in-Blu-ray-and-HD-DVD-movies--/news/75103
| archive-url = https://web.archive.org/web/20080222160135/http://www.heise-online.co.uk/security/Copy-protection-hole-in-Blu-ray-and-HD-DVD-movies--/news/75103
| title = Copy protection hole in Blu-ray and HD DVD movies
| access-date = 2 May 2007
| archive-date = 22 February 2008
|date=7 July 2006
| author = Edward Henning
| work = heise Security}}</ref>

==Patent challenges==
{{main|ECC patents}}
On 30 May 2007, Canadian encryption vendor ] sued Sony alleging that AACS violated two of its patents, "Strengthened public key protocol"<ref>
{{cite web
|url=https://patents.google.com/patent/US6563928
|title=Strengthened public key protocol
|access-date=31 May 2007
|author =Scott A. Vanstone
|date=1 April 1999
|work=US Patent Office
|display-authors=etal}}
</ref> and "Digital signatures on a Smartcard."<ref>
{{cite web
|url=https://patents.google.com/patent/US6704870
|title=Digital signatures on a Smartcard
|access-date=31 May 2007
|author =Scott A. Vanstone
|date=29 August 2001
|work=US Patent Office
|display-authors=etal}}
</ref> The patents were filed in 1999 and 2001 respectively, and in 2003 the ] paid $25 million for the right to use 26 of Certicom's patents, including the two that Sony is alleged to have infringed on.<ref>
{{cite web
|url=https://arstechnica.com/news.ars/post/20070531-encryption-vendor-claims-aacs-infringes-its-patents-sues-sony.html
|title=Encryption vendor claims AACS infringes its patents, sues Sony
|access-date=31 May 2007
|author =Nate Anderson
|date=31 May 2007
|work=Ars Technica
| archive-url= https://web.archive.org/web/20070602130802/http://arstechnica.com/news.ars/post/20070531-encryption-vendor-claims-aacs-infringes-its-patents-sues-sony.html| archive-date= 2 June 2007 | url-status= live}}
</ref>
The lawsuit was dismissed on May 27, 2009.<ref>{{cite web
| url=http://dockets.justia.com/docket/texas/txedce/2:2007cv00216/103383/
| title=Certicom Corporation et al v. Sony Corporation et al Featured Case Has Decisions
| date=2009-05-27
| publisher=justia.com
| access-date=2013-08-12}}</ref>

==See also==
* ]
* ]


==References== ==References==
{{reflist}}
<references />


==External links== ==External links==
{{wikinews|High definition anti-piracy DRM possibly hacked}}
*
* *
* *
* , an introductory forum thread. {{Webarchive|url=https://web.archive.org/web/20120205101739/http://forum.doom9.org/showthread.php?t=122363|date=dmy}} with the diagrams working.
*
* , ISAN as required in the Content ID defined in AACS
* by Hugh Bennett
* , an open source library implementing AACS
* by Hugh Bennett
* , ]'s post on metzdowd.com cryptography mailing list
* by Jeff Lotspiech
*


] {{Digital rights management}}
{{Blu-ray}}
{{HD DVD}}


] ]
]
]
]
]
]
]
]
]
]
]

Latest revision as of 21:53, 22 August 2024

Standard for content distribution and digital rights management
This article needs to be updated. Please help update this article to reflect recent events or newly available information. (August 2017)

AACS decryption process

The Advanced Access Content System (AACS) is a standard for content distribution and digital rights management, intended to restrict access to and copying of the post-DVD generation of optical discs. The specification was publicly released in April 2005. The standard has been adopted as the access restriction scheme for HD DVD and Blu-ray Disc (BD). It is developed by AACS Licensing Administrator, LLC (AACS LA), a consortium that includes Disney, Intel, Microsoft, Panasonic, Warner Bros., IBM, Toshiba and Sony. AACS has been operating under an "interim agreement" since the final specification (including provisions for Managed Copy) has not yet been finalized.

Since appearing in devices in 2006, several AACS decryption keys have been extracted from software players and published on the Internet, allowing decryption by unlicensed software.

System overview

Encryption

AACS uses cryptography to control and restrict the use of digital media. It encrypts content under one or more title keys using the Advanced Encryption Standard (AES). Title keys are decrypted using a combination of a media key (encoded in a Media Key Block) and the Volume ID of the media (e.g., a physical serial number embedded on a pre-recorded disc).

The principal difference between AACS and CSS (the DRM system used on DVDs) lies in how the device decryption keys and codes are organized.

Under CSS, all players of a given model group are provisioned with the same shared activated decryption key. Content is encrypted under the title-specific key, which is itself encrypted under each model's key. Thus each disc contains a collection of several hundred encrypted keys, one for each licensed player model.

In principle, this approach allows licensors to "revoke" a given player model (prevent it from playing back future content) by omitting to encrypt future title keys with the player model's key. In practice, however, revoking all players of a particular model is costly, as it causes many users to lose playback capability. Furthermore, the inclusion of a shared key across many players makes key compromise significantly more likely, as was demonstrated by a number of compromises in the mid-1990s.

The approach of AACS provisions each individual player with a unique set of decryption keys which are used in a broadcast encryption scheme. This approach allows licensors to "revoke" individual players, or more specifically, the decryption keys associated with the player. Thus, if a given player's keys are compromised and published, the AACS LA can simply revoke those keys in future content, making the keys/player useless for decrypting new titles.

AACS also incorporates traitor tracing techniques. The standard allows for multiple versions of short sections of a movie to be encrypted with different keys, while a given player will only be able to decrypt one version of each section. The manufacturer embeds varying digital watermarks (such as Cinavia) in these sections, and upon subsequent analysis of the pirated release the compromised keys can be identified and revoked (this feature is called Sequence keys in the AACS specifications).

Volume IDs

Volume IDs are unique identifiers or serial numbers that are stored on pre-recorded discs with special hardware. They cannot be 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.

To read the Volume ID, a cryptographic certificate (the Private Host Key) signed by the AACS LA is required. However, this has been circumvented by modifying the firmware of some HD DVD and Blu-ray drives.

Decryption process

To view the movie, the player must first decrypt the content on the disc. The decryption process is somewhat convoluted. The disc contains 4 items—the Media Key Block (MKB), the Volume ID, the Encrypted Title Keys, and the Encrypted Content. The MKB is encrypted in a subset difference tree approach. Essentially, a set of keys are arranged in a tree such that any given key can be used to find every other key except its parent keys. This way, to revoke a given device key, the MKB needs only be encrypted with that device key's parent key.

Once the MKB is decrypted, it provides the Media Key, or the km. The km is combined with the Volume ID (which the program can only get by presenting a cryptographic certificate to the drive, as described above) in a one-way encryption scheme (AES-G) to produce the Volume Unique Key (Kvu). The Kvu is used to decrypt the encrypted title keys, and that is used to decrypt the encrypted content.

Analog Outputs

Parts of this article (those related to --This needs to be updated so it doesn't deal mostly with the obsolete HD-DVD format--) need to be updated. Please help update this article to reflect recent events or newly available information. (November 2010)
Main article: Image Constraint Token

AACS-compliant players must follow guidelines pertaining to outputs over analog connections. This is set by a flag called the Image Constraint Token (ICT), which restricts the resolution for analog outputs to 960×540. Full 1920×1080 resolution is restricted to HDMI or DVI outputs that support HDCP. The decision to set the flag to restrict output ("down-convert") is left to the content provider. Warner Pictures is a proponent of ICT, and it is expected that Paramount and Universal will implement down-conversion as well. AACS guidelines require that any title which implements the ICT must clearly state so on the packaging. The German magazine "Der Spiegel" has reported about an unofficial agreement between film studios and electronics manufacturers to not use ICT until 2010 – 2012. However, some titles have already been released that apply ICT.

Audio watermarking

On 5 June 2009, the licensing agreements for AACS were finalized, which were updated to make Cinavia detection on commercial Blu-ray disc players a requirement.

Managed Copy

Managed Copy refers to a system by which consumers can make legal copies of films and other digital content protected by AACS. This requires the device to obtain authorization by contacting a remote server on the Internet. The copies will still be protected by DRM, so infinite copying is not possible (unless it is explicitly allowed by the content owner). It is mandatory for content providers to give the consumer this flexibility in both the HD DVD and the Blu-ray standards (commonly called Mandatory Managed Copy). The Blu-ray standards adopted Mandatory Managed Copy later than HD DVD, after HP requested it.

Possible scenarios for Managed Copy include (but are not limited to):

  • Create an exact duplicate onto a recordable disc for backup
  • Create a full-resolution copy for storage on a media server
  • Create a scaled-down version for watching on a portable device

This feature was not included in the interim standard, so the first devices on the market did not have this capability. It was expected to be a part of the final AACS specification.

In June 2009, the final AACS agreements were ratified and posted online, and include information on the Managed Copy aspects of AACS.

History

On 24 February 2001, Dalit Naor, Moni Naor and Jeff Lotspiech published a paper entitled "Revocation and Tracing Schemes for Stateless Receivers", where they described a broadcast encryption scheme using a construct called Naor-Naor-Lotspiech subset-difference trees. That paper laid the theoretical foundations of AACS.

The AACS LA consortium was founded in 2004. With DeCSS in hindsight, the IEEE Spectrum magazine's readers voted AACS to be one of the technologies most likely to fail in the January 2005 issue. The final AACS standard was delayed, and then delayed again when an important member of the Blu-ray group voiced concerns. At the request of Toshiba, an interim standard was published which did not include some features, like managed copy. On July 5, 2009 the license of AACS1 went online.

Unlicensed decryption

On 26 December 2006, a person using the alias "muslix64" published a working, open-sourced AACS decrypting utility named BackupHDDVD, looking at the publicly available AACS specifications. Given the correct keys, it can be used to decrypt AACS-encrypted content. A corresponding BackupBluRay program was soon developed. Blu-ray Copy is a program capable of copying Blu-rays to the hard drive or to blank BD-R discs.

Security

Main article: Security of Advanced Access Content System

Both title keys and one of the keys used to decrypt them (known as Processing Keys in the AACS specifications) have been found by using debuggers to inspect the memory space of running HD DVD and Blu-ray player programs. Hackers also claim to have found Device Keys (used to calculate the Processing Key) and a Host Private Key (a key signed by the AACS LA used for hand-shaking between host and HD drive; required for reading the Volume ID). The first unprotected HD movies were available soon afterwards. The processing key was widely published on the Internet after it was found and the AACS LA sent multiple DMCA takedown notices in the aim of censoring it. Some sites that rely on user-submitted content, like Digg and Misplaced Pages, tried to remove any mentions of the key. The Digg administrators eventually gave up trying to censor submissions that contained the key.

The AACS key extractions highlight the inherent weakness in any DRM system that permit software players for PCs to be used for playback of content. No matter how many layers of encryption are employed, it does not offer any true protection, since the keys needed to obtain the unencrypted content stream must be available somewhere in memory for playback to be possible. The PC platform offers no way to prevent memory snooping attacks on such keys, since a PC configuration can always be emulated by a virtual machine, in theory without any running program or external system being able to detect the virtualization. The only way to wholly prevent attacks like this would require changes to the PC platform (see Trusted Computing) which could provide protection against such attacks. This would require that content distributors do not permit their content to be played on PCs without trusted computing technology, by not providing the companies making software players for non-trusted PCs with the needed encryption keys.

On 16 April 2007, the AACS consortium announced that it had expired certain encryption keys used by PC-based applications. Patches were available for WinDVD and PowerDVD which used new and uncompromised encryption keys. The old, compromised keys can still be used to decrypt old titles, but not newer releases as they will be encrypted with these new keys. All users of the affected players (even those considered "legitimate" by the AACS LA) are forced to upgrade or replace their player software in order to view new titles.

Despite all revocations, current titles can be decrypted using new MKB v7, v9 or v10 keys widely available in the Internet.

Besides spreading processing keys on the Internet, there have also been efforts to spread title keys on various sites. The AACS LA has sent DMCA takedown notices to such sites on at least one occasion. There is also commercial software (AnyDVD HD) that can circumvent the AACS protection. Apparently this program works even with movies released after the AACS LA expired the first batch of keys.

While great care has been taken with AACS to ensure that contents are encrypted right up to the display device, on the first versions of some Blu-ray and HD DVD software players a perfect copy of any still frame from a film could be made simply by utilizing the Print Screen function of the Windows operating system.

Patent challenges

Main article: ECC patents

On 30 May 2007, Canadian encryption vendor Certicom sued Sony alleging that AACS violated two of its patents, "Strengthened public key protocol" and "Digital signatures on a Smartcard." The patents were filed in 1999 and 2001 respectively, and in 2003 the National Security Agency paid $25 million for the right to use 26 of Certicom's patents, including the two that Sony is alleged to have infringed on. The lawsuit was dismissed on May 27, 2009.

See also

References

  1. Hongxia Jin; Jeffery Lotspiech; Nimrod Megiddo (4 October 2006). "Efficient Traitor Tracing" (PDF). Retrieved 2 May 2007.
  2. "AACS Reference: Pre-recorded Video Book" (PDF). Archived from the original (PDF) on 6 February 2012. Retrieved 2 May 2007.
  3. "Blu-ray Disc Pre-recorded Book" (PDF). AACS LA. 27 July 2006. p. 15. Archived from the original (PDF) on 6 November 2007. Retrieved 1 November 2007.
  4. ^ Reimer, Jeremy (15 April 2007). "New AACS cracks cannot be revoked, says hacker". Ars Technica. Archived from the original on 4 May 2007. Retrieved 4 May 2007.
  5. Geremia (4 April 2007). "Got VolumeID without AACS authentication :)". Doom9.net forums. Archived from the original on 10 May 2007. Retrieved 4 May 2007.
  6. "Advanced Access Content System (AACS): Introduction and Common Cryptographic Elements" (PDF). AACS Licensing Administrator. 17 February 2007. Archived from the original (PDF) on 2 March 2007. Retrieved 5 June 2007.
  7. Sweeting, Paul (19 January 2006). "High-def 'down-converting' forced". Video Business. Archived from the original on 15 April 2006. Retrieved 4 May 2007.
  8. Ken Fisher (21 May 2006). "Hollywood reportedly in agreement to delay forced quality downgrades for Blu-ray, HD DVD". arstechnica.com. Archived from the original on 5 November 2007. Retrieved 2 November 2007.
  9. "HD DVD: "Resident Evil" nur in Standard-Auflösung via YUV". areadvd.de (in German). 29 October 2007. Archived from the original on 11 January 2008. Retrieved 2 November 2007.
  10. "AACS Issues Final Agreements, Enabling Commercial Deployment of Cinavia in Blu-ray Disc Players" (Press release). Verance. 5 June 2009. Archived from the original on 9 October 2009. Retrieved 11 October 2010.
  11. "HP to Support HD-DVD High-definition DVD Format and Join HD-DVD Promotions Group". 5 February 2006. Archived from the original on 4 May 2007. Retrieved 3 May 2007.
  12. ^ Perenson, Melissa J. (21 March 2006). "Burning Questions: No Copying From First High-Def Players". PC World. Archived from the original on 9 October 2007. Retrieved 5 May 2007.
  13. "HD DVD, Blu-ray "Managed Copy" coming later this year". arstechnica.com. 24 May 2007. Archived from the original on 26 May 2010. Retrieved 29 June 2010.
  14. Dan Nicolae Alexa (28 December 2006). "HD DVD's AACS Protection Bypassed. In Only 8 Days?!". playfuls.com. Archived from the original on 10 February 2008. Retrieved 25 October 2007.
  15. Katie Dean (15 July 2004). "Can Odd Alliance Beat Pirates?". Wired. Retrieved 20 January 2015.
  16. Tekla S. Perry (January 2007). "Loser: DVD Copy Protection, Take 2". Spectrum Online. Archived from the original on 8 June 2007. Retrieved 4 May 2007.
  17. Martyn Williams (14 December 2005). "Toshiba Hints at HD-DVD Delay". pcworld.com. Archived from the original on 5 October 2007. Retrieved 19 October 2007.
  18. Craig Morris (14 February 2006). "AACS copy protection for Blu-ray disc and HD DVD delayed again". heise.de. Archived from the original on 2 November 2007. Retrieved 19 October 2007.
  19. Calonge, Juan (8 June 2009). "AACS Final License Goes Online". blu-ray.com. Retrieved 11 March 2023.
  20. Drawbaugh, Ben (24 January 2007). "BackupBluray available now too". Engadget. Archived from the original on 16 May 2007. Retrieved 3 May 2007.
  21. Broida, Rick (9 July 2012). "Get Blu-ray Copy (Win) for free". CNET. Retrieved 18 July 2013.
  22. "HD-DVD Content Protection already hacked?". TechAmok. 28 December 2006. Retrieved 2 January 2007.
  23. "Hi-def DVD security is bypassed". BBC News. 26 January 2007. Archived from the original on 5 May 2007. Retrieved 2 May 2007.
  24. Block, Ryan (20 January 2007). "Blu-ray cracked too?". Engadget. Archived from the original on 23 January 2007. Retrieved 22 January 2007.
  25. Leyden, John (23 January 2007). "Blu-ray DRM defeated". The Register. Archived from the original on 25 January 2007. Retrieved 22 January 2007.
  26. ATARI Vampire (24 February 2007). "WinDVD 8 Device Key Found!". Doom9.net forums. Retrieved 4 May 2007.
  27. jx6bpm (3 March 2007). "PowerDVD private key". Doom9.net forums. Archived from the original on 29 March 2007. Retrieved 4 May 2007.{{cite web}}: CS1 maint: numeric names: authors list (link)
  28. Yam, Marcus (17 January 2007). "First Pirated HD DVDs Released". DailyTech. Archived from the original on 19 February 2007. Retrieved 3 May 2007.
  29. "AACS licensor complains of posted key". Retrieved 2 May 2007.
  30. Boutin (1 May 2007). "Misplaced Pages Locks Out "The Number"". Wired. Archived from the original on 4 May 2007. Retrieved 2 May 2007.
  31. Greenberg, Andy (2 May 2007). "Digg's DRM Revolt". Forbes. Archived from the original on 4 May 2007. Retrieved 4 May 2007.
  32. "DVD DRM row sparks user rebellion". BBC News. 2 May 2007. Archived from the original on 16 May 2007. Retrieved 2 May 2007.
  33. "Press Messages: AACS – Advanced Access Content System". Archived from the original on 30 April 2007. Retrieved 2 May 2007.
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