w3c / w3c/webcodecs

Output of decoding and encoding bytes are fingerprintable

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#231 3 comments 0 reactions 0 assignees View on GitHub

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editorial obsolete privacy-needs-resolution
Dominant language
HTML
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Description

Whilst playing around with the demo code on web.dev we noticed that the output of encoding is different based on the users machine.

I've not extensively tested this by any means however on different Mac machines with different hardware and the same version of Chrome the result was different.

Demo link: https://sand-freckle-pilot.glitch.me/

Example results from Mac machines:

  • New canvas id checksum 7504035
  • New frame id checksum 7502709

and:

  • New canvas id checksum 7504035
  • New frame id checksum 2040000

The differences observed should be outlined in privacy considerations.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Open the linked Glitch demo and compare encoding and decoding outputs across the reported Mac machines. Review the WebCodecs privacy considerations and document the observed machine-dependent differences and their fingerprinting implications, with the examples in this issue as the reference point.

Written by the indexing model from the issue text.

Assessment

Tech stack
html
Domain
documentation, security
Issue type
Documentation
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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