[fallingknife]

> Child abusers evolve and are very happy if law enforcement doesn't.

Yes. And now they will evolve by developing a simple system to modify pixels in images when they copy and transmit that will easily defeat this hashing system. The only effect this will have is that moral panickers like you will have got everybody's privacy invaded over your moral panic of the day.

[heavyset_go]

> And now they will evolve by developing a simple system to modify pixels in images when they copy and transmit that will easily defeat this hashing system

They don't use simple file hashes to match images, but perceptual hashes. That way they can find modified derivatives of a source image. The problem with this approach, though, is that this is ripe for false positives. Two completely unrelated images can have similar hashes.

[sterlind]

could you use multiple perceptual hash functions with different salts, so that collisions would be less likely while allowing derivatives to be detected?

[tatersolid]

That reduces to just inventing a “fancier” single hash function. This adds no value or security in cryptography; it just makes things slower. I expect the same is true of perceptual hashes.

[heavyset_go]

They aren't just matching exact hash hits, but are using a metric like the hamming distance between hashes to determine if one image is the same as , or a derivative of, another. The data structures that allow for efficient lookups rely on that metric, or another metric, for matching.

[mm983]

Again, you don't appear to know how this works. Look up fuzzy hash, i even mentioned it in the comment.

[cronix]

I was a kid in the 80s and teenager in the 90s. My favorite thing during that time was pirating video games. A game would come out, and it was cracked, usually within hours and often before the game was even released to be sold. That's when "zero day" had a different meaning. All the "warez" ftp sites had a section for 0 day warez. The cryptologists and math brains would come up with new protection methods to protect their IP from being copied. Spend millions, probably billions for all of these projects. Yet, some kid in their basement with a commodore 64 was always able to crack them. Sometimes it would take longer. There were a few that took years, but once figured out, unlocked hundreds of titles previously secured.

This is, and always is, a game of cat and mouse. Law enforcement is always catching up. They are the cryptologists here. They are never ahead, always behind, because they don't know the new protections peddlers are using until they have been in use and later discovered.

No matter what vector you plug, they will use another, and the game continues (sick game). Maybe divide the image into 32 different quadrants and rearrange them, then put them back in the correct order when viewing through a specific image viewer. I'm sure that would bypass whatever detections they've come up in their fuzzy fingerprinting with as the entire image is now different. By the time they catch someone using this, they'll have already moved on to something different, as they always do.

I will never be ok with warrantless searches of my personal property, no matter the reason or justification or subject, and no matter who it is done by (government or private company). And I say that as a survivor of some pretty horrific shit as a kid to the point I fucking tremble with absolute rage when thinking about it 35+ years later. I would be banned from everything for life if I were to honestly state what I would do with these types of people. The movie "Saw" is tame in comparison. I have no compassion or sympathy for these sickos. But when reading world history, I can absolutely see the importance of "innocent until proven guilty" and Blackstone's Ratio "It is better that ten guilty persons escape than that one innocent suffer." Most of human history was the opposite, and it was brutal and full of literal witch hunts. Are we progressing as a species, or regressing in terms of human rights when it comes to technology?

[noduerme]

You're spot on about the 0-day comparison. As always, something will arise to let people with the motivation hide illegal images. The problem is how it will be used against everyday citizens, who don't have sophisticated tools and maybe just share images of Hong Kong freedom protests, or books, or anything anti-totalitarian. The emotional appeals about this being about child abuse are absurd on their face because of how easily those people will hide. It's a good thing that some people are able to see through that as a ploy. We shouldn't have to go there and prove our bonafide hatred of abusers every time we justify our right to secure encryption or freedom from surveillance. Doing so almost validates the government's position. Just like in China you would have to say "of COURSE I hate the democracy protesters! I just think..." No, you shouldn't have to take a deep emotional dive into a history of abuse to justify your human right to privacy.

[anthony_d]

Just saying "fuzzy hash" doesn't begin to explain how this would work. There are an infinite variety of algorithms along with arbitrary tolerances configurable. "fuzzy hash" just isn't helpful no matter how many times you repeat it.

[fallingknife]

I have a hard time believing that this algorithm will be able to resist simple image manipulations while still being sensitive enough to avoid false positives.

[diebeforei485]

I have similar qualms with this, because this is increasing the number of photos scanned by 2-3 orders of magnitude, and the number of false positives presumably also increases correspondingly.

[midev]

What algorithm are they using?

[fallingknife]

I don't know. If they made that public it would be completely ineffective.