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The '''security of [[Advanced Access Content System]]''' (AACS) has been a subject of discussion amongst security researchers, high definition video enthusiasts, and consumers at large since its inception. A successor to [[Content Scramble System]] (CSS), the [[digital rights management]] mechanism used by commercial [[DVD]]s, AACS was intended to improve upon the design of CSS by addressing flaws which had led to the [[DeCSS|total circumvention of CSS]] in 1999. The AACS system relies on a [[Tree_Tree (set_theoryset theory)|subset difference tree]] combined with a [[certificate revocation list|certificate revocation]] mechanism to ensure the security of high definition video content in the event of a compromise.
 
Even before AACS was put into use, security researchers expressed doubts about the system's ability to withstand attacks.
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|-
| style="background:#EAEAEA;"| '''[[Cryptography|Algorithm]]'''
| Proprietary [[Linear-feedback shift register|LFSR]]-based
| [[Advanced Encryption Standard|AES]]
|-
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| 128-bit
|-
| style="background:#EAEAEA;"| '''[[Certificate revocation list|Certificate revocation]]'''
| No
| Yes
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{{wikinews|High definition anti-piracy DRM possibly hacked}}
 
The AACS proposal was voted one of the technologies most likely to fail by ''[[IEEE Spectrum]]'' magazine's readers in the January 2005 issue.<ref>{{cite web
| url = http://www.spectrum.ieee.org/jan05/2703
| title = Loser: DVD Copy Protection, Take 2
| accessdate = 2007-05-04
| author = Tekla S. Perry
|date = January 2007
| work = Spectrum Online}}</ref>
|url-status = dead
|archiveurl = https://web.archive.org/web/20070608074811/http://spectrum.ieee.org/jan05/2703
|archivedate = 2007-06-08
}}</ref>
Concerns about the approach included its similarity to past systems that failed, such as CSS, and the inability to preserve security against attacks that compromise large numbers of players. [[Jon Lech Johansen]], who was part of the team that circumvented CSS, said he expected AACS to be cracked by the end of 2006 or the beginning of 2007.<ref>{{cite web
| url = http://nanocrew.net/2006/01/08/deaacscom/
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|work=So sue me}}</ref>
In late 2006, security expert [[Peter Gutmann (computer scientist)|Peter Gutmann]] released "''A Cost Analysis of Windows Vista Content Protection''", a technical paper criticizing the implementation of various content protection technologies in [[Windows Vista]].<ref name=vista-cost>{{cite paperweb
| author = Peter Gutmann
| date = 2006-12-26
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}}
 
Microsoft later claimed that the paper contained various factual errors.<ref>{{cite web|url=http://windowsvistablog.com/blogs/windowsvista/archive/2007/01/20/windows-vista-content-protection-twenty-questions-and-answers.aspx|title=Windows Vista Content Protection - Twenty Questions (and Answers)|url-status=dead|archiveurl=https://web.archive.org/web/20130121121652/http://blogs.windows.com/windows/archive/b/windowsvista/archive/2007/01/20/windows-vista-content-protection-twenty-questions-and-answers.aspx|archivedate=2013-01-21}}</ref><ref>[[Peter Gutmann (computer scientist)#Criticism of Peter Gutmann.27s analysis of Vista DRM]]</ref>
 
While great care had been taken with AACS to ensure that content was encrypted along the entire path from the disc to the [[display device]], it was discovered in July 2006 that a perfect copy of any still frame from a film could be captured from certain [[Blu-ray]] and [[HD DVD]] software players by using the [[Print Screen]] 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
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| date = 2007-01-26
|accessdate=2007-05-02
|work=[[BBC newsNews]]}}</ref><ref>{{cite web
| last = Block
| first = Ryan
| url = httphttps://www.engadget.com/2007/01/20/blu-ray-cracked-too/
| title = Blu-ray cracked too?
| date = 2007-01-20
| accessdate = 2007-01-22
|work=Engadget }}</ref><ref>{{cite web
| url = httphttps://www.theregister.co.uk/2007/01/23/blu-ray_drm_cracked/
| first = John
| last = Leyden
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|title=WinDVD 8 Device Key Found!
|accessdate=2007-05-04
|author="ATARI Vampire"
|date=2007-02-24
|work=Doom9.net forums}}</ref>
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|title=PowerDVD private key
|accessdate=2007-05-04
|author="jx6bpm"
|date=2007-03-03
|work=Doom9.net forums}}</ref>
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|last=Yam
|date=2007-01-17
|work=DailyTech}}</ref>
|archive-date=2007-02-19
|archive-url=https://web.archive.org/web/20070219103102/http://www.dailytech.com/article.aspx?newsid=5747
|url-status=dead
}}</ref>
The Processing Key for the first Media Key Block version, which could be used to decrypt any AACS protected content released up to that point, was found and published on the Internet at the [[Doom9]] forums. AACS Licensing Authority sent multiple [[DMCA takedown notice]]s to web sites hosting the key.<ref>{{cite web
|url=http://www.chillingeffects.org/notice.cgi?sID=3218
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|date=2007-05-02
|work=[[Forbes]]
|url=httphttps://www.forbes.com/technology/2007/05/02/digital-rights-management-tech-cx_ag_0502digg.html
|accessdate=2007-05-04|archiveurl=https://web.archive.org/web/20070504173353/http://www.forbes.com/technology/2007/05/02/digital-rights-management-tech-cx_ag_0502digg.html|archivedate=2007-05-04}}</ref>
Both sites' administrators eventually decided to allow publication of the key.<ref>{{cite web
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|accessdate = 2007-05-02
|date=2007-05-02
|work=[[BBC newsNews]]}}</ref>
 
{{DetailsFurther|AACS encryption key controversy}}
 
[[Cyberlink]], the company which sells the [[PowerDVD]] player, stated that their software could not have been used as part of these exploits.<ref>{{cite web
|date = 2007-01-02
|first =Chris Chris
|last =Lanier Lanier
|url = http://msmvps.com/blogs/chrisl/archive/2007/01/02/463980.aspx
|title = Cyberlink Responds to Alleged AACS Crack
|accessdate = 2007-05-02}}</ref>
|url-status = dead
|archiveurl = https://web.archive.org/web/20070616212554/http://msmvps.com/blogs/chrisl/archive/2007/01/02/463980.aspx
|archivedate = 2007-06-16
}}</ref>
 
On April 16, 2007, the AACS consortium announced that it had revoked the Device Keys used by both Cyberlink PowerDVD and InterVideo [[WinDVD]], and patches were made available for users which provided uncompromised encryption keys and better security for the keys.<ref>{{cite web
|url=http://www.aacsla.com/press/
|title=Press Messages: AACS - Advanced Access Content System
|accessdate=2007-05-02}}</ref>
|archive-date=2007-04-30
|archive-url=https://web.archive.org/web/20070430070403/http://www.aacsla.com/press/
|url-status=dead
}}</ref>
<ref>{{cite web
|url=http://dailytech.com/AACS+Responds+to+Cracked+HD+DVD+and+Bluray+Disc+Protections/article5879.htm
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To continue having the ability to view new content users were forced to apply the patches, which also hardened the security of player applications.
 
On 23 May 2007 the Processing Key for the next version of the Media Key Block was posted to the comments page of a Freedom to Tinker blog post.<ref>{{cite web
|url = http://www.freedom-to-tinker.com/?p=1155#comment-367359
|title = You Can Own an Integer Too
|accessdate = 2007-06-09
|accessdate=2007-06-09}} [http://web.archive.org/web/20070824092116/http://www.freedom-to-tinker.com/?p=1155#comment-367359 Archived copy of page] (original link dead)</ref>
|url-status = bot: unknown
|archiveurl = https://web.archive.org/web/20070824092116/http://www.freedom-to-tinker.com/?p=1155#comment-367359
|archivedate = 2007-08-24
}} (original link dead)</ref>
 
The use of encryption does not offer any true protection against memory snooping, since the software player must have the encryption key available somewhere in memory and there is no way to protect against a determined PC owner extracting the encryption key (if everything else fails the user could run the program in a [[virtual machine]] making it possible to freeze the program and inspect all memory addresses without the program knowing).
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[[SlySoft]] has released [[AnyDVD]] HD which allows users to watch HD DVD and Blu-ray movies on non-[[HDCP]]-compliant PC hardware. The movies can be decrypted on the fly directly from the disc, or can be copied to another medium. AnyDVD HD is also capable of automatically removing any unwanted logos and trailers. Slysoft has 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; this renders it highly vulnerable,<ref>{{cite web
| url = http://forum.slysoft.com/showpost.php?s=dd10095bbb7307dcbb16168166d2087e&p=9286&postcount=2
| title = Device key revokation
| accessdate = 2007-04-09
| date = 2007-02-13
| author = "peer"
|work = Slysoft forums}}</ref>
|url-status = dead
but they will release no details on their implementation. Users at Doom9 claim that the program makes use of the host certificate of [[PowerDVD]] version 6.5,<ref> {{cite web
|archiveurl = https://web.archive.org/web/20070927092642/http://forum.slysoft.com/showpost.php?s=dd10095bbb7307dcbb16168166d2087e&p=9286&postcount=2
|archivedate = 2007-09-27
}}</ref>
but they will release no details on their implementation. Users at Doom9 claim that the program makes use of the host certificate of [[PowerDVD]] version 6.5,<ref>{{cite web
| url = http://forum.doom9.org/showthread.php?t=122272
| title = AnyDVD method of operation
| accessdate = 2007-04-09
| date = 2007-02-15
| author = "evdberg"
| work = Doom9.net Forums }} </ref>
but SlySoft has claimed that the program would be unaffected by the AACS revocation system.<ref>{{cite web
| url = http://forum.slysoft.com/showpost.php?p=15263&postcount=10
| title = And after the process. key is revoked?
| accessdate = 2007-04-09
| date = 2007-03-02
| author = "James"
|work = Slysoft forums }}</ref>
|url-status = dead
|archiveurl = https://web.archive.org/web/20070927092544/http://forum.slysoft.com/showpost.php?p=15263&postcount=10
|archivedate = 2007-09-27
}}</ref>
 
=== Media key block renewals ===
{{Expand section|with=missing details, especially media key blocks #13–#64|small=no|date=December 2022}}
{{Outdated_section|date=December 2015}}
{| class="wikitable"
|-
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| colspan="3" | Never used<ref>{{cite web |url=http://forum.doom9.org/showthread.php?p=1009643#post1009643 |title= New Processing Key found!! (MKB v3 is now open) |accessdate=2007-11-02 |author=aKzenT |date=2007-06-01 |work=doom9.org forums}}</ref>
|-
| [[AACS_encryption_key_controversyAACS encryption key controversy#2007|3]]
| [[The Matrix Trilogy|The ''Matrix'' Trilogy]]
| 2007-05-22
| 2007-05-17<ref>{{cite web |url=http://www.engadgethd.com/2007/05/17/newest-aacs-circumvented-the-matrix-trilogy-set-free/ |title=Newest AACS circumvented: The Matrix Trilogy set free |accessdate=2007-11-02 |author=Thomas Ricker |date=2007-05-17 |work=engadgethd.com}}</ref>
|-
| [[AACS_encryption_key_controversyAACS encryption key controversy#2008|4]]
| ''[[Transformers (film)|Transformers]]'', ''[[Spider-Man 3]]''
|
| 2007-10-30
|-
| 5
| colspan="3" | Never used<ref name="forum.slysoft.com">{{cite web |url=http://forum.slysoft.com/showthread.php?t=15550 |title=AVP: Requiem/Alvin ndand the Cipmunks logfiles |accessdate=2008-04-09 |author= |date= |work=}}</ref>
|-
| [[AACS_encryption_key_controversyAACS encryption key controversy#2008|6]]
| colspan="3" | Never used<ref name="forum.slysoft.com"/>
|-
| [[AACS_encryption_key_controversyAACS encryption key controversy#2008|7]]
| ''[[Alvin and the Chipmunks (film)|Alvin and the Chipmunks]]'', ''[[Aliens vs. Predator: Requiem]]''
| 2008-04-06<ref>{{cite web |url=http://forum.slysoft.com/showthread.php?t=15550 |title=AVP: Requiem/Alvin ndand the Cipmunks logfiles |accessdate=2008-04-09 |author= |date= |work= |publisher=}}</ref>
| 2008-04-11<ref>{{cite web |url=http://forum.slysoft.com/showthread.php?t=15698 |title=AnyDVD (HD) 6.4.1.1 released |accessdate=2008-04-11 |author= |date= |work= |publisher=}}</ref>
|-
| [[AACS_encryption_key_controversyAACS encryption key controversy#2008|8]]
| ''[[The Forbidden Kingdom]]''
| 2008-08-26<ref>{{cite web |url=http://forum.slysoft.com/showthread.php?t=19612 |title=The Forbidden Kingdom (2008) - MKBv8 - Update server down? |accessdate=2008-04-09 |author= |date= |work= |publisher=}}</ref>
| 2008-08-26<ref>{{cite web |url=http://forum.slysoft.com/showthread.php?t=19612 |title=The Forbidden Kingdom (2008) - MKBv8 - Update server down? |accessdate=2008-04-11 |author= |date= |work= |publisher=}}</ref>
|-
| [[AACS_encryption_key_controversyAACS encryption key controversy#2009|9]]
| ?
| Approximately 2008-09-03<ref>{{cite web |url=http://forum.slysoft.com/showthread.php?t=19806&highlight=MKBV9 |title=Blu-ray YELLOW DRAGON'S COLORS Read Error |accessdate=2009-03-28 |author= |date= |work= |publisher=}}</ref>
| 2009-03-20<ref name="MKBvand">{{cite web |url=http://forum.doom9.org/showthread.php?t=145789 |title=MKBv9 and MKBv10 Processing Keys found
|accessdate=2009-03-28 |author= |date= |work= |publisher=}}</ref>
|-
| [[AACS_encryption_key_controversyAACS encryption key controversy#2009|10]]
| ?
| ?
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| ?
|-
| [[AACS_encryption_key_controversyAACS encryption key controversy#2009|12]]
| ''[[Body of Lies (film)|Body of Lies]]'', [[Baraka (film)|Baraka]]
| 2008-10-09
| 2009-04-06<ref>{{cite web |url=http://forum.doom9.org/showpost.php?p=1270338&postcount=156 |title=Disc using MKBv12 decrypted
|accessdate=2009-04-06 |author= |date= |work= |publisher=}}</ref>
|-
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|
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| ?
| Approximately 2018-06-19<ref>{{cite web |url=https://forum.doom9.org/showthread.php?p=1844914#post1844914 |title=Public MKBs |accessdate=2022-12-22 |date=2018-06-19}}</ref>
| ?
|-
| 66
| ?
| Approximately 2018-11-20<ref>{{cite web |url=https://forum.doom9.org/showthread.php?p=1858010#post1858010 |title=Public MKBs |accessdate=2022-12-22 |date=2018-11-20}}</ref>
| ?
|-
| 67
| colspan="3" | Never used<ref name="doom9-post1868374">{{cite web |url=https://forum.doom9.org/showthread.php?p=1868374#post1868374 |title=Public MKBs |accessdate=2022-12-22 |date=2019-03-11}}</ref>
|-
| 68
| ?
| Approximately 2019-03-11<ref name="doom9-post1868374" />
| ?
|-
| 69
| colspan="3" | Never used<ref name="doom9-post1878517">{{cite web |url=https://forum.doom9.org/showthread.php?p=1878517#post1878517 |title=Public MKBs |accessdate=2022-12-22 |date=2019-07-04 |work=doom9.org forums}}</ref>
|-
| 70
| ?
| Approximately 2019-07-04<ref name="doom9-post1878517" />
| ?
|-
| 71
| ?
| ?<ref>{{cite web |url=https://forum.doom9.org/showthread.php?p=1887549#post1887549 |title=Public MKBs |accessdate=2022-12-22 |date=2019-10-15 |work=doom9.org forums |quote=…&nbsp;MKBv71 was identical to MKBv70 as far as HRL/DRL&nbsp;…}}</ref>
| ?
|-
| 72
| ?
| Approximately 2019-10-15<ref name="doom9-post1887549">{{cite web |url=https://forum.doom9.org/showthread.php?p=1887549#post1887549 |title=Public MKBs |accessdate=2022-12-22 |date=2019-10-15 |work=doom9.org forums}}</ref>
| ?
|-
| 73
| colspan="3" | Never used<ref name="doom9-post1906427">{{cite web |url=https://forum.doom9.org/showthread.php?p=1906427#post1906427 |title=Public MKBs |accessdate=2022-12-22 |date=2020-04-05 |work=doom9.org forums}}</ref>
|-
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| colspan="3" | Never used<ref name="doom9-post1906427" />
|-
| 75
| ?
| ?<ref name="doom9-post1970801">{{cite web |url=https://forum.doom9.org/showthread.php?p=1970801#post1970801 |title=Public MKBs |accessdate=2022-12-22 |date=2022-06-24 |work=doom9.org forums |quote=…&nbsp;I found out that MKBv75 does exist. However, HRL/DRL is identical to MKBv72}}</ref>
| ?
|-
| 76
| ?
| Approximately 2020-04-05<ref name="doom9-post1906427" />
| ?
|-
| 77
| ?
| Approximately 2022-06-24<ref name="doom9-post1970801" />
| ?
|-
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| ?
| Approximately 2022-08-02<ref name="doom9-post1972563">{{cite web |url=https://forum.doom9.org/showthread.php?p=1972563#post1972563 |title=Public MKBs |accessdate=2022-12-22 |date=2022-08-02 |work=doom9.org forums}}</ref>
| ?
|}
 
==See also==
* [[AnyDVD]]
 
==References==
Retrieved from "https://en.wikipedia.org/wiki/Security_of_Advanced_Access_Content_System"