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Maybe people concerned about having their voice manipulated can carry a device that generates an acoustic timecode whenever they speak, or at least some kind of

Maybe people concerned about having their voice manipulated can carry a device that generates an acoustic timecode whenever they speak, or at least some kind of non-repeating tone generator. Supposedly the 60Hz or 50Hz hum in recordings can be correlated with variations in the electrical grid frequency. It would make sense to go further and deliberately tag live audio with a timestamp to ensure continuity. I can think of a few ways of faking a timecode like that, but they can be counteracted to an extent.

vortico 10y ago
Interesting. While I think this would make it harder to edit someone's voice, if you're clever enough to design software to read the timecode, you're able to remove it from the spectrum and insert your own with similar room ambience.
- tonyarkles 10y ago
  Not that it's a panacea, but it could be signed with a private key to make it easy to validate whether it's a fake timecode or not. You could include crude, say, cepstral coefficients in with the timecode as well to prevent the timecode from being copy pasted elsewhere.
Waterluvian 10y ago
Do this by autotuning everything I say and I'm sold.
Retr0spectrum 10y ago
It would be trivial to filter out any kind of watermarking. Watermarks get photoshopped out of images all the time. On the other hand, if there was some way to add a watermark that was also a cryptographic signature, you could actually prevent editing. I have no idea how you would implement such a signature system though.
- bradbeattie 10y ago
  Cryptography sign the image sans the least significant bits, then add the signature in said position: http://www.lia.deis.unibo.it/Courses/RetiDiCalcolatori/Progetti98/Fortini/lsb.html http://www.lia.deis.unibo.it/Courses/RetiDiCalcolatori/Proge... Shouldn't be too noticeable. A similar approach should work for audio too.
eriknstr 10y ago
>Supposedly the 60Hz or 50Hz hum in recordings can be correlated with variations in the electrical grid frequency. That's pretty cool. I wonder if this has ever been used to track down someone.

vortico 10y ago

Interesting. While I think this would make it harder to edit someone's voice, if you're clever enough to design software to read the timecode, you're able to remove it from the spectrum and insert your own with similar room ambience.

tonyarkles 10y ago
Not that it's a panacea, but it could be signed with a private key to make it easy to validate whether it's a fake timecode or not. You could include crude, say, cepstral coefficients in with the timecode as well to prevent the timecode from being copy pasted elsewhere.

Waterluvian 10y ago

Do this by autotuning everything I say and I'm sold.

Retr0spectrum 10y ago

It would be trivial to filter out any kind of watermarking. Watermarks get photoshopped out of images all the time. On the other hand, if there was some way to add a watermark that was also a cryptographic signature, you could actually prevent editing. I have no idea how you would implement such a signature system though.

bradbeattie 10y ago
Cryptography sign the image sans the least significant bits, then add the signature in said position: http://www.lia.deis.unibo.it/Courses/RetiDiCalcolatori/Progetti98/Fortini/lsb.html http://www.lia.deis.unibo.it/Courses/RetiDiCalcolatori/Proge... Shouldn't be too noticeable. A similar approach should work for audio too.

eriknstr 10y ago

>Supposedly the 60Hz or 50Hz hum in recordings can be correlated with variations in the electrical grid frequency. That's pretty cool. I wonder if this has ever been used to track down someone.