[Hello71]

according to https://www.bitsoffreedom.nl/2019/12/12/amazons-rekognition-..., current facial recognition software is able to distinguish faces in very blurry mosaics using statistics.

it doesn't matter though. as I've explained, it's far easier to come up with flawed schemes than prove them insecure. just because I can't explain why your specific scheme is insecure doesn't mean it stands a chance against real cryptographers.

[tgsovlerkhgsel]

The 20x26 example is indeed scary, but in line with what was known about facial recognition. (It also becomes a bit less scary when you don't look at a zoomed-in version of the image.)

Hence my suggestion to reduce a face to something like 5x5 blocks.

While I'm familiar with the crypto design problem, this is not a crypto algorithm. Sure, it can't be ruled out that someone in the future will find a way to do it, but the state of the art says that 5x5 pixels are not anywhere near enough to run face recognition.

And a solution that may be broken in the future is often much better than a solution that people don't use because it doesn't meet their needs, which in this case is not having fugly black boxes in their picture.

[Hello71]

this seems like a false dichotomy. there's nothing stopping you from using a pink oval, as long as it covers the face.