Peter Gutmann wrote a nice paper called "
A Cost Analysis of Windows Vista Content Protection" in which he describes the Windows Vista's built-in content protection mechanisms and the considerable costs which are caused by these protections.
I'm going to quote several interesting sentences of his paper:
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)
The fantastic new features of Windows Vista:
- Disabling of Functionality
- Indirect Disabling of Functionality
- Decreased Playback Quality
- Elimination of Open-source Hardware Support
- Elimination of Unified Drivers
- Denial-of-Service via Driver/Device Revocation
- Decreased System Reliability
- Increased Hardware Costs
- Increased Cost due to Requirement to License Unnecessary Third-party IP
- Unnecessary CPU Resource Consumption
- Unnecessary Device Resource Consumption
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). [...] Since S/PDIF doesn't provide any content protection, Vista requires that it be disabled when playing protected content [Note E]. 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.
Elimination of Open-source Hardware Support:
ista 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 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 products.
Decreased System Reliability:
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. [...]
Every little (normally unnoticeable) glitch is suddenly surfaced because it could be a sign of a hack attack, with the required reaction being that (from the spec) “Windows Vista will initiate a full reset of the graphics subsystem, so everything will restart”. According to Microsoft this will only take a few seconds and will only affect the graphics subsystem (so it's not a complete restart of Vista), but the true impact of this mechanism remains to be seen.
Unnecessary CPU Resource Consumption:
In order to prevent active attacks, device drivers are required to poll the underlying hardware every 30ms for digital outputs and every 150 ms for analog ones 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 (Leo Laporte in his Security Now podcast with Steve Gibson calls Vista “an operating system that is insanely paranoid”).
Unnecessary Device Resource Consumption
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.
Have a look at the article - it's a good read.
