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This is dumb. A hash? That's only going to deter the most incompetent internet users when it comes to a file type that is subject to alteration without losing

This is dumb. A hash? That's only going to deter the most incompetent internet users when it comes to a file type that is subject to alteration without losing it's information value (pictures, video, music, etc.). All someone has to do is change a single bit/pixel in the image and the hash will be different. No one will notice that and it defeats the hash. Hell, you don't even have to do that. You can just rotate the image, save it, then rotate it back, and re-save it. The odds are that program that you used will most certainly not write the image data in the same exact way. Hashes would be better for files that cannot be altered without breaking the contents. Although, these could be subject to compression, which would create a new hash. Either way, I think they need to use something similar to Google's image search that actually examines the photo contents for similarity.

sveiss 9y ago
In this case, 'hash' doesn't necessarily mean 'a cryptographic hash of the raw file contents'. There are perceptual hash techniques which still match after changes to the file, and are tuned in a similar manner to lossy compression algorithms to prioritize comparing information relevant to human perceptions. https://www.phash.org/ https://www.phash.org/ is one open-source example.
paulhodge 9y ago
It's not a technical article. I think it's safe to assume that 1) The people implementing this aren't idiots, and 2) The "hash" is probably referring to a "perceptual hash", where very-similar images would show up as the same.
ecopoesis 9y ago
There are hashes that represent the content of photos, the Microsoft’s PhotoDNA and Cloudinary’s pHash. I’m pretty sure Facebook’s engineers are smart enough to that they can’t just run photos through MD5 and have everything work.
oh_sigh 9y ago
It could be a perceptual hash. Who knows? The article doesn't go into detail.

sveiss 9y ago

In this case, 'hash' doesn't necessarily mean 'a cryptographic hash of the raw file contents'. There are perceptual hash techniques which still match after changes to the file, and are tuned in a similar manner to lossy compression algorithms to prioritize comparing information relevant to human perceptions. https://www.phash.org/ https://www.phash.org/ is one open-source example.

paulhodge 9y ago

It's not a technical article. I think it's safe to assume that 1) The people implementing this aren't idiots, and 2) The "hash" is probably referring to a "perceptual hash", where very-similar images would show up as the same.

ecopoesis 9y ago

There are hashes that represent the content of photos, the Microsoft’s PhotoDNA and Cloudinary’s pHash. I’m pretty sure Facebook’s engineers are smart enough to that they can’t just run photos through MD5 and have everything work.

oh_sigh 9y ago

It could be a perceptual hash. Who knows? The article doesn't go into detail.