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Re: [mediacapture-region] Should we support strings in addition or in lieu of opaque identifiers? (#46)

From: Elad Alon via GitHub <sysbot+gh@w3.org>
Date: Fri, 24 Jun 2022 17:33:28 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-1165788089-1656092006-sysbot+gh@w3.org>
> there are many more ways that a uuid could arrive in my app and be manipulated/tracked on the way

Assume we specify:
1. Serializing the same CropTarget multiple times yields different UUIDs. `cropTarget1.serialize() != cropTarget1.serialize()` and ``cropTarget1.serialize() != cropTarget2.serialize()`.
2. CropTargets cannot be compared. `cropTarget1 != cropTarget1` as well as `cropTarget1 != cropTarget2`. Essentially, all comparisons evaluate to false.
3. Calrification: Naturally, deserializing different UUIDs derived from the same CropTarget, derives a CropTarget referencing the same original Element. That's not an issue because of 1 and 2.

Tracking becomes impossible unless you actually get the user to capture the tab from which the CropTarget comes, which is sufficiently rare and user-driven as to be uninteresting. (At that stage, tracking using CropTarget is the least of your worries; you have plenty of other surfaces.)

> A major Video Conference app chooses to offer a server based webAPI for co-operating web apps to submit their cropTargets (to avoid cross origin issues). Perhaps it even penalises sites that don't with a user warning or something.

1. Without an active screen-capture of the tab which minted the CropTarget, the UUID is indistinguishable from nya randomly generated UUID. What good does it do the video conference app to get arbitrary UUIDs that can't be used for tracking?
2. Suppose the video conferencing app has captured another tab. What now? Start checking the billions of CropTargets it's received? Assuming for the sake of argument that it could feasibly reduce the number of reliable candidates - what would it learn of the captured tab, that it would not learn from just examining **all of the app's pixels**, which it's already observing?

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Please view or discuss this issue at https://github.com/w3c/mediacapture-region/issues/46#issuecomment-1165788089 using your GitHub account

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