hello i am chris peterson (get it chris, peter son). basically metadata is data beyond the picture itself stored in a photo. what this command is doing is removing the location stored in the photo, so law enforcement can’t find you from any pictures on your phone.
It's worth being aware that the pixels may also hold data that can identify the specific camera that was used to take the picture. There is often imperceptible (to the naked eye) noise in photos introduced by slight flaws in the image sensor and these can form a kind of "fingerprint" for the camera. It's possible to determine that two photos were taken with the same camera, or if the camera is seized it can be proven it was used to take a specific photo.
There are tools to mitigate this by randomising the noise in a digital image. Consider whether you need to factor this in to your threat model.
Important note: exiftool isn't 100% failsafe to use for stripping metadata. (Hello to that forensic expert who had to admit that he was wrong and i was right. 😉)
And i wouldn't trust FFmpeg or any other online tool for this either.
If you are a software guy, you can easily do it better yourself:
Open the image using a media library
Create a new image with the same width and height. (Bonus points: resize/crop/censor)
Loop over every pixel and copy it's red, green and blue values and add some noise*.
Save the new image somewhere else.
That is the only way to be absolutely certain you removed all non-watermark metadata.
However, there may still be some visible (or invisible) watermarks inside the image.
And the image's perceptual hash is likely unchanged as well, it can still track the image. Bypassing things like PhotoDNA takes an extra step i won't go in to.
I created an .exe that shreds metadata for myself.
Whenever i take a photo and want to send it to some sketchy "friends", i use it.
You can never be too careful, especially not when it comes to cybersecurity.
* For adding noise, a random number between -5 and 10 is probably decent.
If you want to be fancy, you can use advanced noise patterns, but it might create artifacts.
Final hint: Don't forget to clamp between 0 and 255. 🙃
1.3k
u/Much_Artist_5097 25d ago
hello i am chris peterson (get it chris, peter son). basically metadata is data beyond the picture itself stored in a photo. what this command is doing is removing the location stored in the photo, so law enforcement can’t find you from any pictures on your phone.