Re: [csswg-drafts] [css-fonts] incorporate mitigations for font based fingerprinting (#4055)

@hax Thank you!

> Not all OS have good quality CJK fonts installed, currently only HeiTi have good quality fonts broadly available among all major OS. So if you need other high-quality CJK typeface (like Song, Fangsong, Kai, etc.) support, the web page authors may rely on user-installed fonts, for example the fonts which available with MS-Office installation.

From the privacy pespective, it's problematic that for some systems, there isn't a single font bundle. E.g. an en-US install of Windows 10 does have fonts for Chinese but not the ones you mention, but you don't need to install Office: AFAICT, adding the Simplified Chinese IME to available text input methods adds the fonts DengXian, FangSong, KaiTi, and SimHei.

Adding the Japanese and Traditional Chinese IMEs similarly expands the set of fonts even though the en-US base install already has coverage. (And indeed, for Japanese, the base set is gothic-only with no mincho!)

Sites that involve text input can pretty easily figure out what IME a user is using, so in that sense having the font list correlate with IME doesn't give away more information, but when there's no text input on a site or when the user has added IMEs to the menu but isn't currently using them, being able to detect the full set of IMEs the user keeps available is bad. I don't know how to solve this unless Microsoft changes its disk space vs. privacy considerations when deciding how this stuff works, but as long as browsers expose whatever user-installed fonts to the Web, Microsoft has no incentive to change the privacy properties of the system font configurations.

Some privacy can be traded away for typographic quality by not blocking any font that is bundled with Windows even if the font isn't guaranteed to be present in all configurations of Windows.

(I'd expect a Korean font subsetted to the KS X 1001 set of modern-use syllables to be of reasonable size as WOFF2, so the constraints for site-provided fonts for Korean to be different from Chinese and Japanese.)

> A simple assumption behind such strategy is, if user buy/install a font, it's very likely they want to use this font as default font.

Surely that bit of user intent can be seen from the user actually taking action to change the browser font prefs in addition to just installing the font.

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Received on Friday, 27 September 2019 10:50:17 UTC