3 ms·

What would be an exemplary use case for this? Like, when do you ever have images in front of you that are shuffled in this way?

tylfin 5y ago
I could imagine a civil or criminal case relying on shredded documents as a source of evidence.
klyrs 5y ago
When you dumpster dive your competitor looking for trade secrets?
IncRnd 5y ago
We don't shred digital images in RAM in that way, but we can scan & reconstruct physical images that have been shredded or torn. You can paste together possible scenes to construct side-scrolling game scenery in realtime. By applying a few insights we can phase one image into a hole that is in another image. This is similar to randomizing an array by creating a second array with random values, then sorting them in tandem, except we use the TSP with expected weightings. There are lots of use cases for this.
- est31 5y ago
  In the virtual RAM accessible to the process the image might be continuous, but its physical representation could be different, as the operating system might use different areas from the physical RAM to expose it to the process. If you dump a computer's RAM e.g. in a forensic setting, you might attain such a state. Same goes for file systems as well as the wear leveling layer of SSDs.
  - IncRnd 5y ago
    exactly!
clipradiowallet 5y ago
Well, imagine someone dumpster diving at a bank/clinic/insurance provider that doesn't use a document destruction service. Probably plenty of PII/PHI could be reconstructed once the shredded fragments were singulated and scanned.
the8472 5y ago
In the 90s and 00s analog pay tv used to be "encrypted" like this. IIRC software decryption relied on deriving the weak shuffling key by manually reordering image rows and then using that to reverse the key so the next frames could be decrypted more reliably. Doing that kind of video processing in realtime and in software was close to CPU limits. https://en.wikipedia.org/wiki/Nagravision https://en.wikipedia.org/wiki/Nagravision

tylfin 5y ago

I could imagine a civil or criminal case relying on shredded documents as a source of evidence.

klyrs 5y ago

When you dumpster dive your competitor looking for trade secrets?

IncRnd 5y ago

We don't shred digital images in RAM in that way, but we can scan & reconstruct physical images that have been shredded or torn. You can paste together possible scenes to construct side-scrolling game scenery in realtime. By applying a few insights we can phase one image into a hole that is in another image. This is similar to randomizing an array by creating a second array with random values, then sorting them in tandem, except we use the TSP with expected weightings. There are lots of use cases for this.

est31 5y ago
In the virtual RAM accessible to the process the image might be continuous, but its physical representation could be different, as the operating system might use different areas from the physical RAM to expose it to the process. If you dump a computer's RAM e.g. in a forensic setting, you might attain such a state. Same goes for file systems as well as the wear leveling layer of SSDs.
- IncRnd 5y ago
  exactly!

clipradiowallet 5y ago

Well, imagine someone dumpster diving at a bank/clinic/insurance provider that doesn't use a document destruction service. Probably plenty of PII/PHI could be reconstructed once the shredded fragments were singulated and scanned.

the8472 5y ago

In the 90s and 00s analog pay tv used to be "encrypted" like this. IIRC software decryption relied on deriving the weak shuffling key by manually reordering image rows and then using that to reverse the key so the next frames could be decrypted more reliably. Doing that kind of video processing in realtime and in software was close to CPU limits. https://en.wikipedia.org/wiki/Nagravision https://en.wikipedia.org/wiki/Nagravision