Advanced Access Content System: Difference between revisions

Revision as of 03:14, 7 July 2019

Revision as of 02:56, 27 September 2019

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|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

|dead-url-status = yesdead

|df = dmy-all

}}</ref>

=== 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 [[ROM-Mark|BD-ROM Mark]].<ref>{{cite web |url=http://www.aacsla.com/specifications/AACS_Spec_BD_Prerecorded_0.912.pdf |title=Blu-ray Disc Pre-recorded Book |accessdate=2007-11-01 |date=27 July 2006 |publisher=AACS LA |page=15 |archiveurl=https://web.archive.org/web/20071106065659/http://www.aacsla.com/specifications/AACS_Spec_BD_Prerecorded_0.912.pdf |archivedate=6 November 2007 |deadurlurl-status=yesdead |df=dmy-all }}</ref>

To read the Volume ID, a cryptographic [[Public key certificate|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.<ref name=arstechnica-aacs>{{cite web

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|archiveurl=https://web.archive.org/web/20070504171556/http://arstechnica.com/news.ars/post/20070415-aacs-cracks-cannot-be-revoked-says-hacker.html

|archivedate=4 May 2007

|deadurlurl-status=nolive

}}</ref><ref>{{cite web

|url = http://forum.doom9.org/showthread.php?t=124294

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|author = Geremia

|date=4 April 2007

|work=Doom9.net forums| archiveurl= https://web.archive.org/web/20070510023247/http://forum.doom9.org/showthread.php?t=124294| archivedate= 10 May 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</ref>

=== Decryption process ===

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|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

|dead-url-status = yesdead

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{{main|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 [[High-bandwidth Digital Content Protection|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.<ref>{{cite web|url=http://www.videobusiness.com/article/CA6300812.html |title=High-def ‘down-converting’ forced |accessdate=2007-05-04 |date=19 January 2006 |last=Sweeting |first=Paul |work=Video Business |deadurlurl-status=yesdead |archiveurl=https://web.archive.org/web/20060415091053/http://www.videobusiness.com/article/CA6300812.html |archivedate=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 |accessdate=2007-11-02 |author =Ken Fisher |date=21 May 2006 |work=arstechnica.com| archiveurl= https://web.archive.org/web/20071105063630/http://arstechnica.com/news.ars/post/20060521-6880.html| archivedate= 5 November 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</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 |accessdate=2007-11-02 |date=29 October 2007 |work=areadvd.de |language=German |deadurlurl-status=yesdead |archiveurl=https://web.archive.org/web/20080111071532/http://www.areadvd.de/news/2007/200710/29102007001_RE_HD_DVD.shtml |archivedate=11 January 2008 }}</ref>

=== 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.<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 | accessdate = 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 | dead-url-status = yesdead | df = dmy-all }}</ref>

===Managed Copy===

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| title =HP to Support HD-DVD High-definition DVD Format and Join HD-DVD Promotions Group

| accessdate = 2007-05-03

| archiveurl= https://web.archive.org/web/20070504142655/http://www.hp.com/hpinfo/newsroom/press/2005/051216a.html| archivedate= 4 May 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</ref>

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

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|work=arstechnica.com

|accessdate=29 June 2010

| archiveurl= https://web.archive.org/web/20100526040122/http://arstechnica.com/gadgets/news/2007/05/hd-dvd-blu-ray-managed-copy-coming-later-this-year.ars| archivedate= 26 May 2010 <!--DASHBot-->| deadurlurl-status= nolive}}</ref>

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

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== 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?! |accessdate=2007-10-25 |author=Dan Nicolae Alexa |date=28 December 2006 |work=playfuls.com |deadurlurl-status=yesdead |archiveurl=https://web.archive.org/web/20080210005229/http://www.playfuls.com/news_05648_HD_DVDs_AACS_Protection_Bypassed_In_Only_8_Days.html |archivedate=10 February 2008 }}</ref>

The AACS LA consortium was founded in 2004.<ref>{{cite news |url=http://archive.wired.com/entertainment/music/news/2004/07/64212 |title=Can Odd Alliance Beat Pirates? |accessdate=2015-01-20 |author =Katie Dean |date=15 July 2004 |work=Wired }}</ref> 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.<ref>{{cite web

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|archiveurl = https://web.archive.org/web/20070608074811/http://spectrum.ieee.org/jan05/2703

|archivedate = 8 June 2007

|deadurlurl-status = yesdead

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}}</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 |accessdate=2007-10-19 |author=Martyn Williams |date=14 December 2005 |work=pcworld.com |archiveurl=https://web.archive.org/web/20071005171717/http://www.pcworld.com/article/id%2C123924-page%2C1/article.html |archivedate=5 October 2007 |deadurlurl-status=nolive }}</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 |accessdate=2007-10-19 |author =Craig Morris |date=14 February 2006 |work=heise.de | archiveurl= https://web.archive.org/web/20071102222432/http://www.heise.de/english/newsticker/news/69559| archivedate= 2 November 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</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 /> As of 15 October 2007, the final AACS standard had not yet been released.<ref>{{cite web |url=http://www.contentagenda.com/article/CA6491476.html |title=AACS still trying to manage copying |accessdate=2007-10-25 |author =Paul Sweeting |date=15 October 2007 |work=contentagenda.com}}</ref>

==Unlicensed decryption==

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| accessdate = 2007-05-03

|date=24 January 2007

| work = Engadget| archiveurl= https://web.archive.org/web/20070516060453/http://www.engadget.com/2007/01/24/backupbluray-available-now-too/| archivedate= 16 May 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</ref> Blu-ray Copy is a program capable of copying Blu-rays to the [[hard drive]] 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=July 9, 2012|work=[[CNET]]|accessdate=2013-07-18}}</ref>

==Security==

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|date=26 January 2007

|accessdate=2007-05-02

|work=BBC news| archiveurl= https://web.archive.org/web/20070505121314/http://news.bbc.co.uk/2/hi/technology/6301301.stm| archivedate= 5 May 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</ref>

<ref>{{cite web

| last = Block

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|date=20 January 2007

| accessdate = 2007-01-22

|work=Engadget | archiveurl= https://web.archive.org/web/20070123114257/http://www.engadget.com/2007/01/20/blu-ray-cracked-too/| archivedate= 23 January 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</ref>

<ref>{{cite web

| url = https://www.theregister.co.uk/2007/01/23/blu-ray_drm_cracked/

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| title = Blu-ray DRM defeated

|date=23 January 2007

| accessdate = 2007-01-22| archiveurl= https://web.archive.org/web/20070125175901/https://www.theregister.co.uk/2007/01/23/blu-ray_drm_cracked/| archivedate= 25 January 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</ref>

Hackers also claim to have found Device Keys<ref>{{cite web

|url=http://forum.doom9.org/showthread.php?t=122664

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|author ="jx6bpm"

|date=3 March 2007

|work=Doom9.net forums| archiveurl= https://web.archive.org/web/20070329033807/http://forum.doom9.org/showthread.php?t=122969| archivedate= 29 March 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</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

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|archive-url=https://web.archive.org/web/20070219103102/http://www.dailytech.com/article.aspx?newsid=5747

|archive-date=19 February 2007

|dead-url-status=yesdead

|df=dmy-all

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|accessdate=2007-05-02

|date=1 May 2007

|work=Wired| archiveurl= https://web.archive.org/web/20070504012402/http://blog.wired.com/business/2007/05/wikipedia_locks.html| archivedate= 4 May 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</ref>

<ref>{{cite news

|title=Digg's DRM Revolt

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|work=Forbes

|url=https://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= 4 May 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</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

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|accessdate = 2007-05-02

|date=2 May 2007

|work=BBC news| archiveurl= https://web.archive.org/web/20070516215800/http://news.bbc.co.uk/2/hi/technology/6615047.stm| archivedate= 16 May 2007 <!--DASHBot-->| deadurlurl-status= nolive}}</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 [[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.<ref>

{{cite web| url= http://www.aacsla.com/press/| title= Press Messages: AACS – Advanced Access Content System| accessdate= 2007-05-02| archiveurl= https://web.archive.org/web/20070430070403/http://www.aacsla.com/press/| archivedate= 30 April 2007| deadurlurl-status= yesdead| df= dmy-all}}

</ref>

<ref>

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|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

|dead-url-status=yesdead

|df=dmy-all

}}

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|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

|dead-url-status=yesdead

|df=dmy-all

}}

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|date=7 May 2007

|work=Ars Technica

| archiveurl= https://web.archive.org/web/20070520054415/http://arstechnica.com/news.ars/post/20070517-latest-aacs-revision-defeated-a-week-before-release.html| archivedate= 20 May 2007 <!--DASHBot-->| deadurlurl-status= nolive}}

</ref>

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|date=31 May 2007

|work=Ars Technica

| archiveurl= https://web.archive.org/web/20070602130802/http://arstechnica.com/news.ars/post/20070531-encryption-vendor-claims-aacs-infringes-its-patents-sues-sony.html| archivedate= 2 June 2007 <!--DASHBot-->| deadurlurl-status= nolive}}

</ref>