Hardware functionality scan
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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.
Some operating systems 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 unproteced 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
- open-soure drivers: In order support open-source drivers, a hardware manufacturer has to reveal some details about their product, but HFS requires these information to be kept secret.
- generic drivers: The HFS requires indiviudal drivers for each variant of a product, to make them distinguishable: drivers have to account for implementation details instead of using abstract functionality models.
- trusted hardware: 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.