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editorial: Add reading quantization and threshold check algorithms. #77

Merged
merged 2 commits into from
Aug 22, 2022
Merged

editorial: Add reading quantization and threshold check algorithms. #77

merged 2 commits into from
Aug 22, 2022

Commits on Jun 15, 2022

  1. editorial: Add reading quantization and threshold check algorithms. 

    Related to w3c#63, which says the granularity of the data exposed by Ambient
Light Sensors should be specified normatively.

This commit goes a bit further and specifies the two anti-fingerprinting
measures currently implemented by Chrome -- namely, not only are illuminance
values rounded but there's also a threshold value check to avoid storing
values that are too close to the latest reading.

w3c/sensors#429 defines the concepts of "reading quantization algorithm" and
"threshold check algorithm" that concrete sensors can specify. We specify
both here, along with some values used by them (based on the current
Chromium values):

- An "illuminance rounding multiple" of at least 50lx.
- An "illuminance threshold value" of at least 25lx (half the illuminance
  roundig multiple, to be more precise).

These values are then used in the following algorithms:
- The "threshold check algorithm" checks that the difference between new and
  current illuminance values is above the illuminance threshold value.
- The "reading quantization algorithm" rounds up readings to the closest
  multiple of the illuminance rounding multiple.
    @rakuco
    rakuco committed Jun 15, 2022
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  2. Add the "tracking-vector" class to the security section. 

    This follows
https://w3c.github.io/fingerprinting-guidance/#mark-fingerprinting and makes
it clear that this API can increase the fingerprinting surface despite the
proposed mitigations.
    @rakuco
    rakuco committed Jun 15, 2022
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