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Comment by anonytrary | Hacker News Reader

Jokes on them, I have electrical tape on my camera lens. Something I learned from Facebook's CEO, ironically.

The image that's gathered when the camera is completely in the dark, is a unique fingerprint of the camera chip. This is something called "fixed pattern noise."

In that case just put on a few more layers. Shot noise is fairly random.

True. But if you share enough images from the same chip, eventually the fixed pattern noise can be computed to a decent enough accuracy to use it as a fingerprint. Now, you could measure the fixed pattern noise and subtract it from subsequent images. This is a widespread practice in scientific imaging. I'm not devious enough to think of how this could be defeated by someone who really wants to use your camera chip as a fingerprint, but it might be enough to defeat an amateur.

Dark-Signal Non Uniformity (DSNU):

https://harvestimaging.com/blog/?p=814

So likely to provide a few bits of entropy.

You learn some great things on HN!

2006: https://www.researchgate.net/publication/3455253_Digital_Cam...

Notes (by El Gamal of FPGA fame, not cryptography fame): http://isl.stanford.edu/~abbas/ee392b/lect07.pdf

Forensics: https://www.mobiledit.com/camera-ballistics

Anti-forensics (counter-measures/imitation): https://arxiv.org/abs/1707.07795v1 https://www.researchgate.net/publication/305181626_Removing_...

These make a pretty good cover _and_ support the EFF: https://supporters.eff.org/shop/laptop-camera-cover-set

Same, but I like gaff tape because it peels off easy and re-sticks well without leaving a gummy residue

I use my laptop camera every day. I have a neat little plastic thing that can be easily slid back and forth and I am happy with

That can be potentially even easier; if you have a few specks of dust on the camera and your tape leaks a bit of light, they would have a perfect pattern to detect your lens - the specks aren't moving and there will be only speck effects recognizable on any video frame they capture when they max out contrast.

Facebook is using images that people uploaded, and I doubt parent commenter is taking and uploading many pictures with tape over the lens.

FYI: If you cover it with scotch tape some light gets through and the phone/laptop can still use the auto-brighten feature.

I'd love to see people spending >$1,000 on a new iPhone "for the camera", only to cover it with electrical tape.

This sounds like something out of Silicon Valley.

It is rather amazing that smartphone cameras are so feature packed, yet still lack a lens cover. Something as old as cameras themselves.

Old cameras didn't exactly fit in your pocket, and didn't have sapphire glass...

Though I do think it would be nice to have a hardware (iris?) way to close off the camera. Some laptops have this, though I'm sad mine doesn't.

They are available for phones and laptops, e.g. https://www.amazon.com/gp/product/B07B66VZ97/

+1 these are awesome. I have them on all my devices.

That's pretty nice. I'll have to see if I can find some designed for ThinkPads and Samsung phones.

Should work on all Laptops, not sure what's different about ThinkPads. Probably won't work on Samsung phones though.

“Is that a Hasselblad in your pocket, or are just having a really bad day?”

Yes, it would be absurd for any one person to do both of those things, but I highly doubt that has occurred.

But then can’t they just tell it’s you by the tape on the lens?

Because nobody else tapes up their lens?

Dust pattern on the tape.

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