[cojo]

It hadn't occurred to me that even a photo with the lens cap on still contains decent entropy, although it now seems somewhat obvious to me in hindsight after thinking about it.

I really enjoyed how this article covered a variety of different "hacker-spirit" things; real-world entropy into "digital-world" meaningful use cases, plus a whole extra "one more thing" timelock encryption example at the end.

As someone who uses Cloudflare Workers / Pages heavily these days whenever I can, it's quite fun to see both "how the sausage is made" as well as the culture (playfulness?) behind it. Kinda makes me want to go visit the Austin office since I'm local.

Kudos and thanks to the Cloudflare team for writing stuff like this up! One of the more enjoyable tech pieces I've read in the past couple of weeks, and I learned multiple things along the way.

[jareklupinski]

> a photo with the lens cap on still contains decent entropy

https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise

spending so much time devising ways to mitigate or remove noise, it becomes difficult to think of it as a 'feature'...

[flumpcakes]

I worked on research that built machine learning models to take that 'entropy' or sensor pattern noise and to match it against photographs, to trace image lineage when EXIF and similar are stripped out.

For a practical application: as you can imagine, there are certain crimes where it really makes a difference if an image is just on a phone, or if it was verifiably taken by that phone. Possession-of vs. Production-of...

[jjeaff]

That's interesting. But, assuming the research found it possible to verify which device a photo came from based on the sensor noise, doesn't that kind of go against the idea that there is a lot of entropy in sensor pattern noise?

[pclmulqdq]

I spend a lot of time thinking about randomness, and after running some tests on the entropy of dark images, I have started to believe that there is a lot less entropy in dark CCD images than people think, but there is still enough to get a useful entropy stream.

A substantial portion of the "noise" from a CCD is definitely not random.

[KennyBlanken]

The sensor contains decent entropy, assuming you're actually getting raw samples out of the sensor, and your sensor isn't being affected by EMF either in the air or via its power supply.

Noise reduction algorithms are going to affect the entropy if you can't get raw values, and the level of AI crap in cell phone cameras makes it even worse these days.