Advanced Access Content System

The Advanced Access Content System ( AACS ) is a digital rights management ( DRM), which is used in recordable and prerecorded optical media.

The AACS, which also serves as copy protection developed by Intel Corporation, Microsoft, Panasonic, Sony, Toshiba, Walt Disney and Warner Bros..

The authority responsible for the licensing of AACS organization called Advanced Access Content System License Administrator ( AACS LA).

Key Features

AACS tried to combine the core elements of the failed on proprietary encryption algorithm with CSS cryptographic algorithms for a new copy protection system for prerecorded and recordable media.

Components to include:

• Encryption of all contents with AES 128 -bit encryption
• A significantly expanded rights management ( specified in the licensing policies )
• License key management, that is, for example, can also be "protected " copies with limited playing capability are generated (in time or on certain drives )
• Possibility of blocking of license keys
• Drive verification by hardware key
• Encrypted communication between all components to each other
• Network connectivity or Internet possible
• Activation of content via Internet possible
• Expandable list of compatible copy protection systems with exact specification of rights transitions (eg, between AACS and DRM systems from Microsoft).

The aim of AACS is not, so do not take high-resolution video content " unprotected " without encryption and without digital rights management publicly available. This goes beyond the previous copy protection such as a DVD and is a completely self-contained digital rights management.

AACS affects not only prerecorded media and online content eg media servers, but should also extend to high-resolution images from television broadcasts, even those that are sent without encryption, so " free-to -air ".

Moreover, AACS wants but overcome and avoid having a copy to a " dead end " for digital data, when new interfaces and transmission methods are developed, which were not included in the original version of the copy also the " one-way " copy protection.

Realization

AACS is designed as a complete rights management for video data. All content is encrypted using AES -128. The corresponding key is determined by the player from his own Device Key Block and existing on the medium - Media Key Blocks. In the case of pre-recorded media, the media key block for all copies is identical. In blank media every medium has its own individual media key block, so that the recording device for each blank media own, the media key block must produce the medium with inclusive encryption.

In this way it is prevented that it is possible to copy on blank media movies recorded in any number and play on any device ( recording on a DVD -R for example, are not encrypted and are not subject to rights management).

The key management is working with the right management. The aim is that the customer with the AACS encrypted content similar freedoms receives as, for example, are within its budget for unencrypted content on eg VHS tape. In this case, however, restrictions are conceivable, which devices can play the copies and how long they can be played at all ( refer to the signal source but would provide appropriate DRM - control signals, which is not currently the case).

With AACS it should be possible to send protected (encrypted) content over a network, provided that the sender and receiver have appropriate licenses. This assumes that the transfer takes place in turn encrypted. For example, Microsoft plans to provide such functionality with its Windows Media Server. A possible protection method for the transmission of content over a network is DTCP.

In order for a PC can play AACS protected content, must also be a licensed AACS player program be at least next to a AACS - enabled drive (HD DVD or Blu- ray Disc). Its ability to run and the ability to play with AACS "secured " high-resolution movies, may depend on various criteria such as encrypted PCIe bus, HDCP -compliant graphics card and the appropriate operating system patches again.

Analog outputs for the video signal at any time by the rights management completely turned off either on lower resolutions (PAL / NTSC) or scaled down.

This goes so far that AACS defined as amended in 2009, "analog sunset", ie a period of time can be certified within which AACS licensed devices with analog output signals and produces and sells: Only by 2010 it was possible to output the image in high resolution over component outputs ( corresponding devices were allowed to be sold until 2012). Since 2013, no licensing a device with analog video outputs in SD quality ( U.S. and Japan: NTSC, Rest of World: PAL ) is possible. The sale of such devices is set after 2015 also. From 2015 new AACS devices so it will be on sale only with encrypted by HDCP digital video output.

This AACS works makes sense, all components must be dominated by the set- top box recording devices to players AACS (or compatible with AACS copy protection systems). All components must be licensed by the AACS LA (or the licensors of compatible copy protection systems ) and finally AACS must function properly in the interaction of the components.

For a large part of the planned rights management features of HD DVD and Blu- ray Disc, the underlying AACS is responsible, as for the proposed revocation list and to any restrictions in the image output.

Media Support

Currently it obligatory on the following HDTV recording formats, the use of AACS as a DRM system for stored media data:

• HD DVD
• Blu- Ray Disc

Not affected by AACS is the recording format AVCHD. This format corresponds in fact to the file format to build your file structure in the HD DVD and BluRay. In plain language this means that although stand- alone devices in HD DVD and Blu- Ray format will need to record with AACS, but a PC can take on a corresponding drive in AVCHD the same data without AACS.

Criticism

From the user's perspective, there are at AACS the fundamental criticism that it is a comprehensive DRM. This means:

• The " protection" of AACS extends unlike previous systems not only on prerecorded media, but it will ( without the user can do something about it ) which were previously unprotected formats (such as free to air television broadcasts ) packed in the DRM system whenever recording on an appropriate AACS compliant device is started.
• To once a DRM contained content (ie high-definition video ) is not let out again from the rights management, are the obligation HDCP to be used as " protection" on the video and audio output of the playback systems, older systems such as HDTV displays and A / V systems effectively locked out or supplied only with inferior signals. This restriction is currently given only at the request of content, the latest from about 2016 but newly manufactured equipment may then have no analog signal outputs more.
• In addition, provided in the AACS special data blocks to drive HDCP outputs. This analog outputs switched off and even block lists subsequently locked HDCP device IDs can be transferred.
• In AACS is the risk that a legally acquired player at any time, can not play without the influence of the owner, AACS protected media, as soon as this device has been set by the AACS LA on the black list of hacked devices. This is because each device is equipped with a device key which is required to decrypt the protected data. Using this key allows devices that have been cracked for any reason, at any time be recognized and made ​​retroactively unusable. Each volume contains indeed a blacklist with no more permissible device keys, this list can be updated by the AACS LA any time soon as a user inserts a new volume with a current blacklist, in which his unit is no longer allowed into his player, the device is made as prohibited branded and playing unusable. This last step will then lead that older disks that have been played before without problems, can no longer be played on this unit. It should be noted that the end user has no control over whether the device key of his own playback device is cracked somewhere in the world from one other person, as the device key can occur in a series of multiple devices of the same type.
• Unlike the CSS the DVD is available from AACS player software for use on computers no permanent key, but the keys player the player software must be replaced in approximately 1.5 - yearly basis. This will make it impossible, for example, to obtain, after 2011 or HDTV content on a connected via D-Sub analog monitor, as certified after 2010 players this functionality may no longer offer.

Copy protection problem in the HDTV

Even with HDCP has been shown that the industry sometimes takes years until a cryptographic copy protection is implemented in reasonably usable form (HDCP dated from 1999, and it took until 2005 until the first seal of quality HD ready by equipment manufacturers gave the documented explicitly HDCP at least one input). If one assumes that the offered from spring 2006 HD systems (HD DVD and Blu- ray Disc) will represent the first implementations of AACS, it can be assumed that the interested of HD content buyer in addition to the high cost of new developed instruments are also feeling the discomfort of Erstimplementierungen of AACS, this is at the complete DRM systems is always a risk that already licensed devices for reasons that are out of control of the customer, will lose their licenses and thus be useless for the user.

Next is the fact that there are already approaches to a fully independent of AACS form of " digital rights control" in the area of ​​high-definition video: TV, forcing their customers, a delicate for a broadcast flag set- top box to receive to use, lock in broadcasting, for example a movie, the analog outputs or scale them down to SDTV quality. The HDTV signal then only via a digital, but encrypted by HDCP output, but generally should not be recorded.

If the major movie studios with their intention, the award of broadcasting rights for HDTV broadcasts of feature films to the sending of a binding " broadcast flag" should prevail, recording devices would generally questionable for HDTV content: only left unprotected transmissions such as news programs or sports events then even record in high resolution. Also a HDTV recorder with AACS support will not be able to record HDCP - encrypted content of a digital image transmission, since HDCP to the necessary rights management is lacking, because activated HDCP corresponds to the permission level "must not be recorded ."

Only receivers with an AACS -compliant digital signal output can then optionally deliver a recordable signal, but again, it is questionable as a receiving device then considering a set broadcast flag, the permission settings within the AACS transfer sets to the recording device, or whether, given the possibility to install a hard drive in the receiving device, generally will be those instruments with a AACS -compliant digital video interface.

Dispute over the "perfect " copy protection between HD DVD and Blu -ray

Around the summer of 2005, the tide between the two competing formats for the benefit of cheaper produced HD DVD seemed to turn. To get more studios on its side, broke a race for the better copy protection between HD DVD and Blu -ray Disc: After BD initially completely without copy came along ( PC drives and standalone first-generation devices that were only sold in Japan and chronicled only in MPEG2), was first announced by the respective manufacturers, and Blu -ray will work with AACS copy protection.

The Blu -ray Disc Association does not meet even the former restrictions on the HDTV playback within AACS: you implement in their BD said system additionally executable Java applets on the Blu- ray Disc These programs run on the player hardware or - software in a virtual machine and check in the background, if the output current is manipulated. Notes BD a change, so the output is canceled. However, BD makes no changes to the hardware or software of the player. The first discs with BD are published during the year 2007. From the Manufacturer SlySoft appeared in March 2008 with AnyDVD HD is the first software that can bypass this protection.

BD is not directly a component of AACS, but is a copy that is specific for BD player. However, there is the possibility that BD and AACS complement each other, making it difficult to levering the copy protection. AACS is an implementation on BD players and BD in some details.

Delays in copy protection standard and "analog sunset"

The potential extensions of AACS have long meant that the standard was not adopted in the final version, although were already HD DVD and Blu- Ray player built and sold. The corresponding devices were certified according to an interim standard.

Because despite the intention of the copyright holders in the U.S., the appropriate FCC directive to the forced introduction of a broadcast flag in the summer of 2005 was tipped just before the legal validity and to the problem of still not successful introduction of HDCP inputs on all HDTVs sold deal, the AACS LA decided to allow the provisional version 0.9 of the AACS specification even with an analog output. This is first in assembled from autumn 2007 devices the CGMS -A said analog copy protection included ( a kind of " Macrovision for HDTV" ), from 2010 certified equipment should then only SDTV output on analog outputs, and from 2013 certified devices are then no analog enable signal output more. This rule can be found in the AACS specification, entitled "analog sunset", or " analog sunset " again and corresponds to the intention of the U.S. film industry to banish than easily copied branded analogue signal outputs.

The final version of AACS was not published until 2009 (four years after the launch of HD DVD and BD). It was determined that as of 2014 no BD player longer be sold, the analog video outputs include ( analog component outputs from 2011 no longer be operated with HDTV resolution).

Summary of the criticism

In summary, it should be noted that the film industry and equipment manufacturers are planning the introduction of AACS, actually recording and gain full control over the owned by private individuals for video playback devices. Would be solely controlled by control signals in the data stream of high-resolution images then the recording devices refuse admission or only in inferior resolution record to a complete cessation of functions of the devices. The rights holder could take affect how long a picture remains playable. These restrictions could not be reversed as long as the content on the protection of AACS are. AACS is so designed that the protection remains maximum even across system boundaries, to the consequence that, for example, is no analog image output more.

What AACS completely missing is a reliable for the user way to permanently to get to the protected in the AACS content in High Definition: There is no reliable interface, which can be packaged in the AACS content to spend again in full quality to devices that are neither HDCP still AACS know. This applies to video as audio data.

Through the use of AES -128 very safe encryption method, it is also very unlikely that AACS will ever hacked so extensive as was the case with the CSS of DVD. However, some "hacks " of software players or players can be neutralized by the fact that the corresponding key is placed on the revocation list of AACS. The software of these devices then you have, at best, to be replaced within a specified period against an again "safe" version, so that the device or program at all still works - the manufacturer is condemned, however, for breach of the license agreement to pay a fine or goes bankrupt, can this generally mean the end for the equipment, the customer would then have left behind.

Due to the temporary key lending to software player ( the validity of the key by hardware players seem to be not limited in time ), the user is in fact also forced, for example, replace PC components, if the new version of the software player z. example, no longer wants to work with an older OS version, or with a certain drive or graphics card.

Attacks on AACS

End of December 2006, there is a programmer named " Muslix64 " demonstrated how to bypass the AACS copy protection. However, the protection is not cracked, but only avoided - because the files are apparently copied together with the original keys. The need for decryption "Title Keys " he could determine by a defect in a software player. This sets the Title Keys unencrypted from the main memory of the computer. A program written by him Java program " HDDVDBackup " decrypted with the found Title Keys below the material and copied it to the hard drive. Currently, this is possible with the media HD DVD and Blu -ray Disc.

Although the program requires yet the previously identified key of the media, from the next version it is but they can identify themselves. The hack has been documented only by a video entitled " AACS is unbreakable". By his own account, the hacker took only eight days to bypass the AACS protection.

According to information the programmer is the ability to decrypt the data material are preserved even when the software player permission to decrypt by putting on a revocation list should be withdrawn. The program was published in 2007.

On 28 January 2007, the individual keys of the various films were found. This message has been confirmed by the manufacturers or studios.

On 14 February 2007, " Arnezami " forum member of the Doom9 site, discovered claims to a Universal key for HD - DVD and Blu- ray formats. He could show that both Blu -ray media and HD DVD discs use one and the same " Processing Key".

Although all AACS concerned Hacks unable to compromise certain media or players or playback programs, but are not so far advanced that the copy itself would be so wirklungslos, as is the case for example with the CSS DVD-Video.

The background is that in contrast to the CSS at AACS no new encryption standard was created, which turned out to be faulty and vulnerable to attack in hindsight, but instead with AES cryptographically tested and widely accepted encryption is used so that only errors in the design of AACS ( but, apart from the general design issues with DRM, were not found ) or can be exploited in the implementation of a hack.

Implementation errors are, for example, the use of a uniform Processing Keys for all current Blu-ray releases as well as the unprotected ( against the AACS License Terms offending ) transfer the disk ID in the HD - DVD drive of the Xbox 360

Currently, several programs claim (eg AnyDVD HD, DVDFab Blu- ray to Blu -ray) for to be able to bypass the AACS protection on all data currently on the market HD media.