Windows Vista Nightmare!

Custo de usar o Windows Vista, e o(s) pesadelo(s) que este sistema introduz em toda a cadeia do TI.

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           A Cost Analysis of Windows Vista Content Protection

                Peter Gutmann,
                     Last updated 28 December 2006

Executive Summary

Windows Vista includes an extensive reworking of core OS elements in order to
provide content protection for so-called "premium content", typically HD data
from Blu-Ray and HD-DVD sources.  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).  This document
analyses the cost involved in Vista's content protection, and the collateral
damage that this incurs throughout the computer industry.

Executive Executive Summary

The Vista Content Protection specification could very well constitute the
longest suicide note in history.


This document looks purely at the cost of the technical portions of Vista's
content protection [Note A].  The political issues (under the heading of DRM)
have been examined in exhaustive detail elsewhere and won't be commented on
further, unless it's relevant to the cost analysis.  However, one important
point that must be kept in mind when reading this document is that in order to
work, Vista's content protection must be able to violate the laws of physics,
something that's unlikely to happen no matter how much the content industry
wishes it were possible [Note B].  This conundrum is displayed over and over
again in the Windows content-protection requirements, with manufacturers being
given no hard-and-fast guidelines but instead being instructed that they need
to display as much dedication as possible to the party line.  The
documentation is peppered with sentences like:

  "It is recommended that a graphics manufacturer go beyond the strict letter
  of the specification and provide additional content-protection features,
  because this demonstrates their strong intent to protect premium content".

This is an exceedingly strange way to write technical specifications, but is
dictated by the fact that what the spec is trying to achieve is fundamentally
impossible.  Readers should keep this requirement to display appropriate
levels of dedication in mind when reading the following analysis [Note C].

Disabling of Functionality

Vista's content protection mechanism only allows protected content to be sent
over interfaces that also have content-protection facilities built in.
Currently the most common high-end audio output interface is S/PDIF
(Sony/Philips Digital Interface Format).  Most newer audio cards, for example,
feature TOSlink digital optical output for high-quality sound reproduction,
and even the latest crop of motherboards with integrated audio provide at
least coax (and often optical) digital output.  Since S/PDIF doesn't provide
any content protection, Vista requires that it be disabled when playing
protected content [Note D].  In other words if you've sunk a pile of money
into a high-end audio setup fed from an S/PDIF digital output, you won't be
able to use it with protected content.  Similarly, component (YPbPr) video
will be disabled by Vista's content protection, so the same applies to a high-
end video setup fed from component video.

Indirect Disabling of Functionality

As well as overt disabling of functionality, there's also covert disabling of
functionality.  For example PC voice communications rely on automatic echo
cancellation (AEC) in order to work.  AEC requires feeding back a sample of
the audio mix into the echo cancellation subsystem, but with Vista's content
protection this isn't permitted any more because this might allow access to
premium content.  What is permitted is a highly-degraded form of feedback that
might possibly still sort-of be enough for some sort of minimal echo
cancellation purposes.

The requirement to disable audio and video output plays havoc with standard
system operations, because the security policy used is a so-called "system
high" policy: The overall sensitivity level is that of the most sensitive data
present in the system.  So the instant any audio derived from premium content
appears on your system, signal degradation and disabling of outputs will
occur.  What makes this particularly entertaining is the fact that the
downgrading/disabling is dynamic, so if the premium-content signal is
intermittent or varies (for example music that fades out), various outputs and
output quality will fade in and out, or turn on and off, in sync.  Normally
this behaviour would be a trigger for reinstalling device drivers or even a
warranty return of the affected hardware, but in this case it's just a signal
that everything is functioning as intended.

Decreased Playback Quality

Alongside the all-or-nothing approach of disabling output, Vista requires that
any interface that provides high-quality output degrade the signal quality
that passes through it if premium content is present.  This is done through a
"constrictor" that downgrades the signal to a much lower-quality one, then up-
scales it again back to the original spec, but with a significant loss in
quality.  So if you're using an expensive new LCD display fed from a high-
quality DVI signal on your video card and there's protected content present,
the picture you're going to see will be, as the spec puts it, "slightly
fuzzy", a bit like a 10-year-old CRT monitor that you picked up for $2 at a
yard sale [Note E].  In fact the specification specifically still allows for
old VGA analog outputs, but even that's only because disallowing them would
upset too many existing owners of analog monitors.  In the future even analog
VGA output will probably have to be disabled.  The only thing that seems to be
explicitly allowed is the extremely low-quality TV-out, provided that
Macrovision is applied to it.

The same deliberate degrading of playback quality applies to audio, with the
audio being downgraded to sound (from the spec) "fuzzy with less detail" 
[Note F].

Amusingly, the Vista content protection docs say that it'll be left to
graphics chip manufacturers to differentiate their product based on
(deliberately degraded) video quality.  This seems a bit like breaking the
legs of Olympic athletes and then rating them based on how fast they can
hobble on crutches.

Beyond the obvious playback-quality implications of deliberately degraded
output, this measure can have serious repercussions in applications where
high-quality reproduction of content is vital.  For example the field of
medical imaging either bans outright or strongly frowns on any form of lossy
compression because artifacts introduced by the compression process can cause
mis-diagnoses and in extreme cases even become life-threatening.  Consider a
medical IT worker who's using a medical imaging PC while listening to
audio/video played back by the computer (the CDROM drives installed in
workplace PCs inevitably spend most of their working lives playing music or
MP3 CDs to drown out workplace noise).  If there's any premium content present
in there, the image will be subtly altered by Vista's content protection,
potentially creating exactly the life-threatening situation that the medical
industry has worked so hard to avoid.  The scary thing is that there's no easy
way around this - Vista will silently modify displayed content under certain
(almost impossible-to-predict in advance) situations discernable only to
Vista's built-in content-protection subsystem [Note G].

Elimination of Open-source Hardware Support

In order to prevent the creation of hardware emulators of protected output
devices, Vista requires a Hardware Functionality Scan (HFS) that can be used
to uniquely fingerprint a hardware device to ensure that it's (probably)
genuine.  In order to do this, the driver on the host PC performs an operation
in the hardware (for example rendering 3D content in a graphics card) that
produces a result that's unique to that device type.

In order for this to work, the spec requires that the operational details of
the device be kept confidential.  Obviously anyone who knows enough about the
workings of a device to operate it and to write a third-party driver for it
(for example one for an open-source OS, or in general just any non-Windows OS)
will also know enough to fake the HFS process.  The only way to protect the
HFS process therefore is to not release any technical details on the device
beyond a minimum required for web site reviews and comparison with other

Elimination of Unified Drivers

The HFS process has another cost involved with it.  Most hardware vendors have
(thankfully) moved to unified driver models instead of the plethora of
individual drivers that abounded some years ago.  Since HFS requires unique
identification and handling of not just each device type (for example each
graphics chip) but each variant of each device type (for example each stepping
of each graphics chip) to handle the situation where a problem is found with
one variation of a device, it's no longer possible to create one-size-fits-all
drivers for an entire range of devices like the current
Catalyst/Detonator/ForceWare drivers.  Every little variation of every device
type out there must now be individually accommodated in custom code in order
for the HFS process to be fully effective.

If a graphics chip is integrated directly into the motherboard and there's no
easy access to the device bus then the need for bus encryption (see
"Unnecessary CPU Resource Consumption" below) is removed.  Because the
encryption requirement is so onerous, it's quite possible that this means of
providing graphics capabilities will suddenly become more popular after the
release of Vista.  However, this leads to a problem: It's no longer possible
to tell if a graphics chip is situated on a plug-in card or attached to the
motherboard, since as far as the system is concerned they're both just devices
sitting on the AGP/PCIe bus.  The solution to this problem is to make the two
deliberately incompatible, so that HFS can detect a chip on a plug-in card vs.
one on the motherboard.  Again, this does nothing more than increase costs and
driver complexity.

Further problems occur with audio drivers.  To the system, HDMI audio looks
like S/PDIF, a deliberate design decision to make handling of drivers easier.
In order to provide the ability to disable output, it's necessary to make HDMI
codecs deliberately incompatible with S/PDIF codecs, despite the fact that
they were specifically designed to appear identical in order to ease driver
support and reduce development costs.

Denial-of-Service via Driver Revocation

Once a weakness is found in a particular driver or device, that driver will
have its signature revoked by Microsoft, which means that it will cease to
function (details on this are a bit vague here, presumably some minimum
functionality like generic 640x480 VGA support will still be available in
order for the system to boot).  This means that a report of a compromise of a
particular driver or device will cause all support for that device worldwide
to be turned off until a fix can be found [Note H].  Again, details are
sketchy, but if it's a device problem then presumably the device turns into a
paperweight once it's revoked.  If it's an older device for which the vendor
isn't interested in rewriting their drivers (and in the fast-moving hardware
market most devices enter "legacy" status within a year of two of their
replacement models becoming available), all devices of that type worldwide
become permanently unusable.

An example of this might be nVidia TNT2 video cards, which are still very
widely deployed in business environments where they're all that you need to
run Word or Outlook or Excel (or, for that matter, pretty much any non-gaming
application).  The drivers for these cards haven't been updated for quite some
time for exactly that reason: You don't need the latest drivers for them
because they're not useful with current games any more (if you go to the
nVidia site and try and install any recent drivers, the installer will tell
you to go back and download much older drivers instead).  If a TNT2 device
were found to be leaking content, it seems unlikely that nVidia would be
interested in reviving discontinued drivers that it hasn't touched for several
years, creating instant orphanware of the installed user base.

The threat of driver revocation is the ultimate nuclear option, the crack of
the commissars' pistols reminding the faithful of their duty [Note I].  The
exact details of the hammer that vendors will be hit with is buried in
confidential licensing agreements, but I've heard mention of multi-million
dollar fines and embargoes on further shipment of devices alongside the driver
revocation mentioned above.

This revocation can have unforeseen carry-on costs.  Windows' anti-piracy
component, WGA, is tied to system hardware components.  Windows allows you to
make a small number of system hardware changes after which you need to renew
your Windows license (the exact details of what you can and can't get away
with changing has been the subject of much debate).  If a particular piece of
hardware is deactivated (even just temporarily while waiting for an updated
driver to work around a content leak) and you swap in a different video card
or sound card to avoid the problem, you risk triggering Windows' anti-piracy
measures, landing you in even more hot water.  If you're forced to swap out a
major system component like a motherboard, you've instantly failed WGA
validation. Revocation of any kind of motherboard-integrated device
(practically every motherboard has some form of onboard audio, and all of the
cheaper ones have integrated video) would appear to have a serious negative
interaction with Windows' anti-piracy measures.

The details of what will happen if a motherboard contains unused onboard audio
capabilities and an additional sound card alongside it, and the motherboard
drivers are revoked, is unknown.  Windows can't tell that there's nothing
connected to the onboard audio because the user prefers to use their M-Audio
Revolution 7.1 Surround Sound card instead, so it'll probably have to revoke
the motherboard drivers even though they're not used for anything. Since
virtually all motherboards contain onboard audio, this could prove quite

An entirely different DoS problem that applies more to HDMI-enabled devices in
general has already surfaced in the form of, uhh, "DVI amplifiers", which take
as input an HDMI signal and output a DVI signal, amplifying it in the process.
Oh, and as a side-effect they forget to re-apply the HDCP protection to the
output.  These devices are relatively simple to design and build using off-
the-shelf HDMI chips.  Beyond the commercially-available models, individual
hardware hackers have built their own protection-strippers using chip samples
obtained from chip vendors.  If you have the right credentials you can even
get hardware evaluation boards designed for testing and development that do
this sort of thing.  And I won't even get into the territory of HD players
with non-HDMI digital outputs, for example ones that contain an HD-SDI (SMPTE
292M) interface.  HD-SDI is an unencrypted digital link typically used in TV
studios but also available from various non-US sources as after-market
sidegrades for standard HD players, providing better-than-HDMI image quality
without the hassle of HDCP.

Now assume that the "DVI amplifier" manufacturer buys a truckload of HDMI
chips (they'll want to get as many as they can in one go because they probably
won't be able to go back and buy more when the chip vendor discovers what
they're being used for).  Since this is a rogue device, it can be revoked...
along with hundreds of thousands or even millions of other consumer devices
that use the same chip.  Engadget have a good overview of this scenario at

(Exactly what will happen when a key is leaked depends on how the attackers
handle it.  The way HD-DVD/Blu-Ray keying works is that a per-device key is
used to decrypt the title key on the disk, and the title key is then in turn
used to decrypt the content.  So the chain of custody is Device key -> Title
key -> Content.  This level of indirection allows an individual device to be
disabled by revoking the device key without making the disk unplayable on all
devices, since other device keys can still decrypt the title key and thus the
content (I've simplified this a bit to cut down the length of the explanation,
see the AACS specification for more details).

The device key is tied to a particular device/player/vendor, but the title key
is only tied to the content on disk.  You can probably see where this is
going... by publishing the device key, the attacker can cause general mayhem
by forcing device revocation.  On the other hand by publishing the title key
the attacker can release the content in an untraceable manner, since it's not
known which device key was used to leak the title key.  In addition since
there's no way to un-publish the title key (encrypted content + title key =
unencrypted content), at that point it's game over for the content).

Decreased System Reliability

  "Drivers must be extra-robust.  Requires additional driver development to
  isolate and protect sensitive code paths" -- ATI.

Vista's content protection requires that devices (hardware and software
drivers) set so-called "tilt bits" if they detect anything unusual.  For
example if there are unusual voltage fluctuations, maybe some jitter on bus
signals, a slightly funny return code from a function call, a device register
that doesn't contain quite the value that was expected, or anything similar, a
tilt bit gets set.  Such occurrences aren't too uncommon in a typical
computer.  For example starting up or plugging in a bus-powered device may
cause a small glitch in power supply voltages, or drivers may not quite manage
device state as precisely as they think.  Previously this was no problem - the
system was designed with a bit of resilience, and things will function as
normal.  In other words small variances in performance are a normal part of
system functioning.  Furthermore, the degree of variance can differ widely
across systems, with some handling large changes in system parameters and
others only small ones.  One very obvious way to observe this is what happens
when a bunch of PCs get hit by a momentary power outage.  Effects will vary
from powering down, to various types of crash, to nothing at all, all
triggered by exactly the same external event.

With the introduction of tilt bits, all of this designed-in resilience is
gone.  Every little (normally unnoticeable) glitch is suddenly surfaced
because it could be a sign of a hack attack.  The effect that this will have
on system reliability should require no further explanation.

Content-protection "features" like tilt bits also have worrying denial-of-
service (DoS) implications.  It's probably a good thing that modern malware is
created by programmers with the commercial interests of the phishing and spam
industries in mind rather than just creating as much havoc as possible.  With
the number of easily-accessible grenade pins that Vista's content protection
provides, any piece of malware that decides to pull a few of them will cause
considerable damage.  The homeland security implications of this seem quite
serious, since a tiny, easily-hidden piece of malware would be enough to
render a machine unusable, while the very nature of Vista's content protection
would make it almost impossible to determine why the denial-of-service is
occurring.  Furthermore, the malware authors, who are taking advantage of
"content-protection" features, would be protected by the DMCA against any
attempts to reverse-engineer or disable the content-protection "features" that
they're abusing.

Even without deliberate abuse by malware, the homeland security implications
of an external agent being empowered to turn off your IT infrastructure in
response to a content leak discovered in some chipset that you coincidentally
happen to be using is a serious concern for potential Vista users.  Non-US
governments are already nervous enough about using a US-supplied operating
system without having this remote DoS capability built into the operating
system.  And like the medical-image-degradation issue, you won't find out
about this until it's too late, turning Vista PCs into ticking time bombs if
the revocation functionality is ever employed.

Increased Hardware Costs

  "Cannot go to market until it works to specification... potentially more
  respins of hardware" -- ATI.

  "This increases motherboard design costs, increases lead times, and reduces
  OEM configuration flexibility.  This cost is passed on to purchasers of
  multimedia PCs and may delay availability of high-performance platforms" --

Vista includes various requirements for "robustness" in which the content
industry, through "hardware robustness rules", dictates design requirements to
hardware manufacturers.  For example, only certain layouts of a board are
allowed in order to make it harder for outsiders to access parts of the board.
Possibly for the first time ever, computer design is being dictated not by
electronic design rules, physical layout requirements, and thermal issues, but
by the wishes of the content industry.  Apart from the massive headache that
this poses to device manufacturers, it also imposes additional increased costs
beyond the ones incurred simply by having to lay out board designs in a
suboptimal manner.  Video card manufacturers typically produce a one-size-
fits-all design (often a minimally-altered copy of the chipset vendor's
reference design), and then populate different classes and price levels of
cards in different ways.  For example a low-end card will have low-cost,
minimal or absent TV-out encoders, DVI circuitry, RAMDACs, and various other
add-ons used to differentiate budget from premium video cards. You can see
this on the cheaper cards by observing the unpopulated bond pads on circuit
boards, and gamers and the like will be familiar with cut-a-trace/resolder-a-
resistor sidegrades of video cards.  Vista's content-protection requirements
eliminate this one-size-fits-all design, banning the use of separate TV-out
encoders, DVI circuitry, RAMDACs, and other discretionary add-ons.  Everything
has to be custom-designed and laid out so that there are no unnecessary
accessible signal links on the board.  This means that a low-cost card isn't
just a high-cost card with components omitted, and conversely a high-cost card
isn't just a low-cost card with additional discretionary components added,
each one has to be a completely custom design created to ensure that no signal
on the board is accessible.

This extends beyond simple board design all the way down to chip design.
Instead of adding an external DVI chip, it now has to be integrated into the
graphics chip, along with any other functionality normally supplied by an
external chip.  So instead of varying video card cost based on optional
components, the chipset vendor now has to integrate everything into a one-
size-fits-all premium-featured graphics chip, even if all the user wants is a
budget card for their kid's PC.

Increased Cost due to Requirement to License Unnecessary Third-party IP

  "We've taken on more legal costs in copyright protection in the last six to
  eight months than we have in any previous engagement.  Each legal contract
  sets a new precedent, and each new one builds on the previous one" -- ATI.

Protecting all of this precious premium content requires a lot of additional
technology.  Unfortunately much of this is owned by third parties and requires
additional licensing.  For example HDCP for HDMI is owned by Intel, so in
order to send a signal over HDMI you have to pay royalties to Intel, even
though you could do exactly the same thing for free over DVI.  Similarly,
since even AES-128 on a modern CPU isn't fast enough to encrypt high-bandwidth
content, companies are required to license the Intel-owned Cascaded Cipher, an
AES-128-based transform that's designed to offer a generally similar level of
security but with less processing overhead.

The need to obtain unnecessary technology licenses extends beyond basic
hardware IP.  In order to demonstrate their commitment to the cause, Microsoft
have recommended as part of their "robustness rules" that vendors license
third-party code obfuscation tools to provide virus-like stealth capabilities
for their device drivers in order to make it difficult to interfere with their
operations or reverse-engineer them.  Vendors like Cloakware and Arxan have
actually added "robustness solutions" web pages to their sites in anticipation
of this lucrative market.  This must be a nightmare for device vendors, for
whom it's already enough of a task getting fully functional drivers deployed
without having to deal with adding stealth-virus-like technology on top of the
basic driver functionality.

The robustness rules further complicate driver support by disallowing features
such as driver debugging facilities in shipping drivers.  Most Windows XP
users will at one time or another have encountered a Windows crash message
indicating that some application that they were using has terminated
unexpectedly, and would they like to send debugging information to Microsoft
to help fix the problem.  Some device vendors even implement their own custom
versions of this debugging support in their drivers, an example being ATI's
VPU Recover, which captures graphics diagnostic and debugging information to
send to ATI when a graphics device problem occurs.  Since this debugging
functionality could leak content or content security information, it can no
longer be used with audio or video components, considerably complicating
vendors' driver support and software enhancement processes (the ATI product
manager referenced in the "Sources" section lists these additional testing and
support costs as "potentially the highest cost of all").

Unnecessary CPU Resource Consumption

  "Since [encryption] uses CPU cycles, an OEM may have to bump the speed grade
  on the CPU to maintain equivalent multimedia performance.  This cost is
  passed on to purchasers of multimedia PCs" -- ATI.

In order to prevent tampering with in-system communications, all communication
flows have to be encrypted and/or authenticated.  For example content sent to
video devices has to be encrypted with AES-128.  This requirement for
cryptography extends beyond basic content encryption to encompass not just
data flowing over various buses but also command and control data flowing
between software components.  For example communications between user-mode and
kernel-mode components are authenticated with OMAC message authentication-code
tags, at considerable cost to both ends of the connection.

In order to prevent active attacks, device drivers are required to poll the
underlying hardware every 30ms to ensure that everything appears kosher.  This
means that even with nothing else happening in the system, a mass of assorted
drivers has to wake up thirty times a second just to ensure that... nothing
continues to happen.  In addition to this polling, further device-specific
polling is also done, for example Vista polls video devices on each video
frame displayed in order to check that all of the grenade pins (tilt bits) are
still as they should be.  We already have multiple reports from Vista
reviewers of playback problems with video and audio content, with video frames
dropped and audio stuttering even on high-end systems.  Time will tell whether
this problem is due to immature drivers or has been caused by the overhead
imposed by Vista's content protection mechanisms interfering with playback.
An indication of the level of complexity added to the software can be seen by
looking at a block diagram of Vista's Media Interoperability Gateway (MIG). Of
the eleven components that make up the MIG, only two (the audio and video
decoders) are actually used to render content.  The remaining nine are used to
apply content-protection measures.

On-board graphics create an additional problem in that blocks of precious
content will end up stored in system memory, from where they could be paged to
disk.  In order to avoid this, Vista tags such pages with a special protection
bit indicating that they need to be encrypted before being paged out and
decrypted again after being paged in.  Vista doesn't provide any other
pagefile encryption, and will quite happily page banking PINs, credit card
details, private, personal data, and other sensitive information, in
plaintext.  The content-protection requirements make it fairly clear that in
Microsoft's eyes a frame of premium content is worth more than (say) a user's
medical records or their banking PIN [Note J].

In addition to the CPU costs, the desire to render data inaccessible at any
level means that video decompression can't be done in the CPU any more, since
there isn't sufficient CPU power available to both decompress the video and
encrypt the resulting uncompressed data stream to the video card.  As a
result, much of the decompression has to be integrated into the graphics chip.
At a minimum this includes IDCT, MPEG motion compensation, and the Windows
Media VC-1 codec (which is also DCT-based, so support via an IDCT core is
fairly easy).  As a corollary to the "Increased Hardware Costs" problem above,
this means that you can't ship a low-end graphics chip without video codec
support any more.

The inability to perform decoding in software also means that any premium-
content compression scheme not supported by the graphics hardware can't be
implemented.  If things like the Ogg video codec ever eventuate and get used
for premium content, they had better be done using something like Windows
Media VC-1 or they'll be a non-starter under Vista or Vista-approved hardware.
This is particularly troubling for the high-quality digital cinema (D-Cinema)
specification, which uses Motion JPEG2000 (MJ2K) because standard MPEG and
equivalents don't provide sufficient image quality.  Since JPEG2000 uses
wavelet-based compression rather than MPEG's DCT-based compression, and
wavelet-based compression isn't on the hardware codec list, it's not possible
to play back D-Cinema premium content (the moribund Ogg Tarkin codec also used
wavelet-based compression).  Because *all* D-Cinema content will (presumably)
be premium content, the result is no playback at all until the hardware
support appears in PCs at some indeterminate point in the future.  Compare
this to the situation with MPEG video, where early software codecs like the
XingMPEG en/decoder practically created the market for PC video.  Today,
thanks to Vista's content protection, the opening up of new markets in this
manner would be impossible.

The high-end graphics and audio market are dominated entirely by gamers, who
will do anything to gain the tiniest bit of extra performance, like buying
Bigfoot Networks' $250 "Killer NIC" ethernet card in the hope that it'll help
reduce their network latency by a few milliseconds.  These are people buying
$500-$1000 graphics and sound cards for which one single sale brings the
device vendors more than the few cents they get from the video/audio portion
of an entire roomful of integrated-graphics-and-sound PCs.  I wonder how this
market segment will react to knowing that their top-of-the-line hardware is
being hamstrung by all of the content-protection "features" that Vista hogties
it with?

Unnecessary Device Resource Consumption

  "Compliance rules require [content] to be encrypted.  This requires
  additional encryption/decryption logic thus adding to VPU costs.  This cost
  is passed on to all consumers" -- ATI.

As part of the bus-protection scheme, devices are required to implement
AES-128 encryption in order to receive content from Vista.  This has to be
done via a hardware decryption engine on the graphics chip, which would
typically be implemented by throwing away a GPU rendering pipeline or two to
make room for the AES engine.

Establishing the AES key with the device hardware requires further
cryptographic overhead, in this case a 2048-bit Diffie-Hellman key exchange
whose 2K-bit output is converted to a 128-bit AES key via a Davies-Meyer hash
with AES as its block transformation component.  In programmable devices this
can be done (with considerable effort) in the device (for example in
programmable shader hardware), or more simply by throwing out a few more
rendering pipelines and implementing a public-key-cryptography engine in the
freed-up space.

Needless to say, the need to develop, test, and integrate encryption engines
into audio/video devices will only add to their cost, as covered in "Increased
Hardware Costs" above, and the fact that they're losing precious performance
in order to accommodate Vista's content protection will make gamers less than

Final Thoughts

  "No amount of coordination will be successful unless it's designed with the
  needs of the customer in mind.  Microsoft believes that a good user
  experience is a requirement for adoption" -- Microsoft.

  "The PC industry is committed to providing content protection on the PC, but
  nothing comes for free.  These costs are passed on to the consumer" -- ATI.

At the end of all this, the question remains: Why is Microsoft going to this
much trouble?  Ask most people what they picture when you use the term
"premium-content media player" and they'll respond with "A PVR" or "A DVD
player" and not "A Windows PC".  So why go to this much effort to try and turn
the PC into something that it's not?

In July 2006, Cory Doctorow published an analysis of the anti-competitive
nature of Apple's iTunes copy-restriction system ("Apple's Copy Protection
Isn't Just Bad For Consumers, It's Bad For Business", Cory Doctorow,
Information Week, 31 July 2006).  The only reason I can imagine why Microsoft
would put its programmers, device vendors, third-party developers, and
ultimately its customers, through this much pain is because once this copy
protection is entrenched, Microsoft will completely own the distribution
channel.  In the same way that Apple has managed to acquire a monopolistic
lock-in on their music distribution channel (an example being the Motorola
ROKR fiasco, which was so crippled by Apple-imposed restrictions that it was
dead the moment it appeared), so Microsoft will totally control the premium-
content distribution channel.  Not only will they be able to lock out any
competitors, but because they will then represent the only available
distribution channel they'll be able to dictate terms back to the content
providers whose needs they are nominally serving in the same way that Apple
has already dictated terms back to the music industry: Play by Apple's rules,
or we won't carry your content. The result will be a technologically enforced
monopoly that makes their current de-facto Windows monopoly seem like a velvet
glove in comparison.

Overall, Vista's content-protection functionality seems like an astonishingly
short-sighted piece of engineering, concentrating entirely on content
protection with no consideration given to the enormous repercussions of the
measures employed.  It's something like the PC equivalent of the (hastily
dropped) proposal mooted in Europe to put RFID tags into high-value banknotes
as an anti-counterfeiting measure, completely ignoring the fact that the major
users of this technology would end up being criminals who would use it to
remotely identify the most lucrative robbery targets.

The worst thing about all of this is that there's no escape.  Hardware
manufacturers will have to drink the kool-aid (and the reference to mass
suicide here is deliberate [Note K]) in order to work with Vista: "There is no
requirement to sign the [content-protection] license; but without a
certificate, no premium content will be passed to the driver".  Of course as a
device manufacturer you can choose to opt out, if you don't mind your device
only ever being able to display low-quality, fuzzy, blurry video and audio
when premium content is present, while your competitors don't have this
(artificially-created) problem.

As a user, there is simply no escape.  Whether you use Windows Vista, Windows
XP, Windows 95, Linux, FreeBSD, OS X, Solaris (on x86), or almost any other
OS, Windows content protection will make your hardware more expensive, less
reliable, more difficult to program for, more difficult to support, more
vulnerable to hostile code, and with more compatibility problems.  Because
Windows dominates the market and device vendors are unlikely to design and
manufacture two different versions of their products, non-Windows users will
be paying for Windows Vista content-protection measures in products even if
they never run Windows on them.

Here's an offer to Microsoft: If we, the consumers, promise to never, ever,
ever buy a single HD-DVD or Blu-Ray disc containing any precious premium
content [Note L], will you in exchange withhold this poison from the computer
industry?  Please?


This document was put together with input from various sources, including a
number that requested that I keep their contributions anonymous (in some cases
I've simplified or rewritten some details to ensure that the original,
potentially traceable wording of non-public requirements docs isn't used).
Because it wasn't always possible to go back to the sources and verify exact
details, it's possible that there may be some inaccuracies present, which I'm
sure I'll hear about fairly quickly.  No doubt Microsoft (who won't want a
view of Vista as being broken by design to take root) will also provide their
spin on the details.

In addition to the material present here, I'd be interested in getting further
input both from people at Microsoft involved in implementing the content
protection measures and from device vendors who are required to implement the
hardware and driver software measures.  I know from the Microsoft sources that
contributed that many of them care deeply about providing the best possible
audio/video user experience for Vista users and are quite distressed about
having to spend time implementing large amounts of anti-functionality when
it's already hard enough to get things running smoothly without the
intentional crippling.  I'm always open to further input, and will keep all
contributions confidential unless you give me permission to repeat something.
If you're concerned about traceability, grab a disposable account at Hotmail,
Gmail, or some similar provider and contact me through that.  If you want to
encrypt things, my PGP key is linked from my home page,

(In case the above hints aren't obvious enough, if you work for nVidia, ATI,
VIA, SiS, Intel, ..., I'd *really* like to get your comments on how all of
this is affecting you).


Because this writeup started out as a private discussion in email, a number of
the sources used were non-public.  The best public sources that I know of are:

"Output Content Protection and Windows Vista",, from WHDC.

"Windows Longhorn Output Content Protection",,
from WinHEC.

"How to Implement Windows Vista Content Output Protection",,
from WinHEC.

"Protected Media Path and Driver Interoperability Requirements",,
from WinHEC.

(Note that the cryptography requirements have changed since some of the
information above was published.  SHA-1 has been deprecated in favour of
SHA-256 and SHA-512, and public keys seem to be uniformly set at 2048 bits in
place of the mixture of 1024 bits and 2048 bits mentioned in the

An excellent analysis from one of the hardware vendors involved in this comes
from ATI, in the form of "Digital Media Content Protection",,
from WinHEC.  This points out (in the form of PowerPoint bullet-points) the
manifold problems associated with Vista's content-protection measures, with
repeated mention of increased development costs, degraded performance and the
phrase "increased costs passed on to consumers" pervading the entire
presentation like a mantra.

In addition there have been quite a few writeups on this (although not going
into quite as much detail as this document) in magazines both online and in
print, one example being PC World's feature article "Will your PC run Windows
Vista?",, which covers this in the
appropriately-titled section "Multimedia in chains".  Audience reactions to
these proposals at WinHEC are covered in "Longhorn: tough trail to PC digital
media" published in EE Times 
unfortunately you need to be a subscriber to read this but you may be able to
find accessible cached copies using your favourite search engine.


This document seems to produce various comments that come up repeatedly.  To
respond to the more frequent ones, I've added this mini-FAQ.

1. This is just Microsoft-bashing.

It's bad-technology bashing.  If this had been done by Linus Torvalds, Steve
Jobs, Alan Cox, or Theo de Raadt, I'd have said the same thing about it.  As
far as I'm concerned computers are tools to get a job done and not a platform
for religious wars, and if something's bad I'll say so regardless of who's
doing it.  Just for the record I run various versions of Windows on ...
[counting] ... seven of my machines (the rest are a mixture of Linux, FreeBSD,
and occasionally Solaris), which would make me a rather unlikely Microsoft
detractor if I have their software all over my machines.

2. This is a biased writeup.

Perhaps, but then I challenge anyone to read the specifications given in the
"Sources" section above and write a positive analysis of Vista's content
protection.  Someone has to point out these problems, and it happened to be me
in this case, but I think anyone with technical skills who reads the relevant
documents would come to a similar conclusion.

3. This is all FUD/rubbish.

The process that leads to comments like this tends to be (1) Quickly skim
through this document, (2) Decide that it sounds a bit implausible (possibly
even before performing step 1), (3) Post a rant saying it's FUD.  To pick one
particular example, a Digg reader says a comment that there isn't sufficient
CPU power available for both decompression and encryption:

  I'm sorry, where does this come from? You do realize that this is completely
  uncited, and very likely wrong? Entire paragraphs that follow are based on
  this magical detail pulled out of thin air. [...] I'm no fan of this
  asinine DRM bullshit, but the scenarios and postulates put forth in this
  article are complete rubbish.

Referring to the very first source listed in the "Sources" section shows that
this is picked not from thin air but from Microsoft's own documentation:

  The problem with regular AES is that it takes about 20 CPU clocks to encrypt
  each byte. This is OK for compressed or semi-compressed video, but for the
  multiple HD uncompressed case, it is too much even for a 2006 processor.

and then again:
  In the case of premium content, whether video can play back smoothly when
  using regular AES with uncompressed video will be a function of the
  resolution of the uncompressed video and the power of the processor. It is
  unlikely to work well in 2006 for uncompressed HD premium content

If you don't believe what you read here, go back to Microsoft's own
documentation and read that (in fact read the Microsoft documents no matter
what you believe, because they're quite scary).  If you still think it's FUD
then you can at least post informed comments about it.

4. You're just upset because you can no longer steal content under Vista.

Yes, someone really did send me email with this claim in it.  It's silly
enough that I just had to include it for the amusement value :-).

Use, Modification, and Redistribution

This document is licensed under the Creative Commons Attribution 2.5 License,  This means that you can copy,
distribute, display, and perform the work, and make derivative works, provided
that you credit the original author and provide a link back to the original
work (at the URL given in the title).  To quote the Creative Commons site,
"This license lets others distribute, remix, tweak, and build upon your work,
even commercially, as long as they credit you for the original creation.  This
is the most accommodating of licenses offered, in terms of what others can do
with your works".


Note A: This document uses "cost" in the sense of "penalty", "damage", "harm",
"injury" and "loss" rather than the more financial "expense", "outlay", and
"price".  A full financial analysis would require a top-to-bottom internal
audit of the design, development, production, distribution, support, and legal
costs for each vendor involved, something for which even the vendors
themselves would have difficulty producing a precise figure.

Note B: I'll make a prediction at this point that, given that it's trying to
do the impossible, the Vista content protection will take less than a day to
bypass if the bypass mechanism is something like a driver bug or a simple
security hole that applies only to one piece of code (and can therefore be
quickly patched), and less than a week to comprehensively bypass in a
driver/hardware-independent manner.  This doesn't mean it'll be broken the day
or week that it appears, but simply that once a sufficiently skilled attacker
is motivated to bypass the protection, it'll take them less than a day or a
week to do so.

(In a recent development which is still subject to change as more reports come
in, a sort of re-run of the DeCSS/Xing player story from a few years ago has
occurred when someone appeared to have figured out how to extract HD-DVD and
Blu-Ray keys from the PowerDVD player software, allowing all(?) HD disk
content to be decrypted and played back on any HD display, without content-
protection measures getting in the way.  The fact that the legally-purchased
content wouldn't play on a legally-purchased player because the content
protection got in the way appears to have been the motivating factor for the
crack.  The time taken was about a week).

Note C: In order for content to be displayed to users, it has to be copied
numerous times.  For example if you're reading this document on the web then
it's been copied from the web server's disk drive to server memory, copied to
the server's network buffers, copied across the Internet, copied to your PC's
network buffers, copied into main memory, copied to your browser's disk cache,
copied to the browser's rendering engine, copied to the render/screen cache,
and finally copied to your screen.  If you've printed it out to read, several
further rounds of copying have occurred.  Windows Vista's content protection
(and DRM in general) assume that all of this copying can occur without any
copying actually occurring, since the whole intent of DRM is to prevent
copying.  If you're not versed in DRM doublethink this concept gets quite
tricky to explain, but in terms of quantum mechanics the content enters a
superposition of simultaneously copied and uncopied states until a user
collapses its wave function by observing the content (in physics this is
called quantum indeterminacy or the observer's paradox).  Depending on whether
you follow the Copenhagen or many-worlds interpretation of quantum mechanics,
things then either get wierd or very wierd.  So in order for Windows Vista's
content protection to work, it has to be able to violate the laws of physics
and create numerous copies that are simultaneously not copies.

Note D: There is SCMS, but that has all the effectiveness of a "Keep out"

Note E: As an example of an experience that's likely to become commonplace
once more "premium content" is rolled out, Roger Strong reports from Canada
that "I've just had my first experience with HD content being blocked.  I
purchased an HP Media Center PC with a built-in HD DVD player, together with a
24" 'high definition' 1920 x 1200 HP flat panel display (HP LP2465).  They
even included an HD movie, 'The Bourne Supremacy'.  Sure enough, the movie
won't play because while the video card supports HDCP content protection, the
monitor doesn't.  (It plays if I connect an old 14" VGA CRT using a DVI-to-VGA
connector)".  "muslix64" tells a similar tale: "when I disable my HD monitor,
I can watch the movie, on my old VGA screen, but, what is the point of having
a HD monitor and not being able to watch a HD movie on it".

Note F: The question of how content producers other than the major studios who
can afford expensive custom equipment are supposed to create and manipulate
high-definition content has been raised by a number of readers.  For example
one contributor who works with people in the content industry comments that "I
have seen [smaller content producers] going from just recording weddings and
the like, to ones that have gone all the way to make a full featured movie.
They have gone through problems like where to edit HD material, which cameras
to use, which format, etc.  Their decisions have been based on availability of
equipment to make their projects, not really costs".  It has been suggested
that the large content producers are quite happy with this situation, since it
prevents any competition from more innovative, creative, and agile newcomers.

Note G: Philip Dorrell has a neat cartoon that illustrates this problem at

Note H: There is some confusion over exactly how much functionality gets
disabled when a revocation occurs.  The HDCP requirements are quite clear that
once this happens (in technical terms once a revoked device's key selection
vector (KSV, effectively it's unique ID) appears on a revocation list) the
device is effectively dead since it won't be supplied with content any more.
However the behaviour of devices subject to revocation in a mixed-content
environment is made very unclear in the specs.  Some documents imply that it's
an HDCP-style kill switch ("Vista will [...] revoke any driver that is found
to be leaking premium content [...] if the same driver is used for all the
manufacturer's chip designs, then a revocation would cause all that company's
products to need a new driver"), while others indicate that the device will
still work, but be unable to render premium content.  Exactly how well this
hope can be realised in practice (if it can be realised at all) remains to be

Note I: I see some impressive class-action suits to follow if this revocation
mechanism is ever applied.  Perhaps Microsoft or the content providers will
buy everyone who owns a device that inadvertently leaks content and is then
disabled by the revocation process replacement hardware for their system.

Some contributors have commented that they can't see the revocation system
ever being used because the consumer backlash would be too enormous, but then
the legal backlash from not going ahead could be equally extreme.  For anyone
who's read "Guns of August", the situation seems a bit like pre-WWI Europe
with people sitting on step 1 of enormously complex battle plans that can't be
backed out of once triggered, no matter how obvious it is that going ahead
with them is a bad idea.  Driver revocation is a lose/lose situation for
Microsoft, they're in for some serious pain whether they do or they don't.
Their lawyers must have been asleep when they let themselves get painted into
this particular corner - the first time a revocation takes out a hospital,
foreign government department, air traffic control system, or whatever,
they've guaranteed themselves a front-row seat in court proceedings for the
rest of their natural lives.

Note J: The Enterprise and Ultimate editions of Vista do feature this type of
encryption, but the features of these high-end versions will never get into
the hands of typical users.  In addition it's an all-or-nothing encryption
where (to quote Microsoft) "all user and system files are encrypted" when what
really counts is swap-file encryption, since that's what contains copies of
sensitive in-memory data.  The OpenBSD approach of generating a random swap-
file encryption key at boot time and encrypting any memory data that gets
paged to disk is the correct way to handle this.

Note K: The "kool-aid" reference may be slightly unfamiliar to non-US readers,
it's a reference to the 1978 Jonestown mass-suicide in which Jim Jones'
followers drank Flavor Aid laced with poison in order to demonstrate their
dedication to the cause.  In popular usage the term "kool-aid" is substituted
for Flavor Aid because it has more brand recognition.  There's also an
earlier, less well-known link to fruit juice laced with LSD, I'll avoid the
obvious comment about that and some of the thinking behind Vista's content

Note L: If I do ever want to play back premium content, I'll wait a few years
and then buy a $50 Chinese-made set-top player to do it, not a $1000 Windows
PC.  It's somewhat bizarre that I have to go to communist China in order to
find vendors who actually understand the consumer's needs.

A reductio ad absurdum solution to the "premium-content problem", proposed by
a Slashdot reader, is to add support to Windows Vista for a black-box hardware
component that accepts as input encrypted compressed premium content and
produces as output encrypted (or otherwise protected) decoded premium content.
In other words, move the entire mass of hardware, driver, and software
protection into a dedicated black box that's only used in media PCs where it's
(arguably) required.

Now compare this add-on black box to the canonical Chinese-made $50 media
player.  Why would anyone buy the black box (which will almost certainly cost
more than $50) when they can buy a complete dedicated media player that does
the same thing and more?

Scary HU????

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