A Hardware Functionality Scan (HFS) is conducted in order to verify that a certain device is really what it claims to be. It's patented by Microsoft

Microsoft

Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

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Some operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

s only send copy protected content, such as movies, to an output device, such as the screen, if that device is able to protect the content from being tapped in an unprotected format. This mechanism can be circumvented by letting fake hardware claiming to be a trusted device. HFS prevents this by letting the device perform certain tasks which are hard to emulate.

Problems

In order to support open-source drivers, a hardware manufacturer has to reveal some details about their product, but HFS requires this information to be kept secret. The problem with generic drivers is that the HFS requires individual drivers for each variant of a product To make them distinguishable, drivers have to account for implementation details instead of using abstract functionality models. A hardware manufacturer has to have his product's HFS fingerprint listed in the database of trusted hardware in order to make it work under newer Windows operating systems. Thus, Microsoft dictates the conditions under which a device is accepted. The manufacturer may be required to implement certain DRM-features for which he has to pay a royalty to its respective inventor.

Sources

• A Cost Analysis of Windows Vista Content Protection
• patent description