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The Problem with Perceptual Hashes

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Re: The Problem with Perceptual Hashes

#51

Post by mattigames »

emodendroket wrote: post #34
rustybolt wrote: post #16

> an Apple employee will then look at your (flagged) pictures. This means that there will be people paid to look at child pornography and probably a lot of private nude pictures as well.

And what do you think the content moderation teams employed by Facebook, YouTube, et al. do all day?

Yeah, we obviously needed one more company doing it as well, and I'm sure having more positions in the job market which pretty much could be described as "Get paid to watch pedophilia all day long" will not backfire in any way.

Re: The Problem with Perceptual Hashes

#52

Post by new_realist »

marcinzm wrote: post #27

Given all the zero day exploits on iOS I wonder if it's now going to be viable to hack someone's phone and upload child porn to their account. Apple with happily flag the photos and then, likely, get those people arrested. Now they have to, in practice, prove they were hacked which might be impossible. Will either ruin their reputation or put them in jail for a long time. Given past witch hunts it could be decades be…

This is already possible using other services (Google Drive, gmail, Instagram, etc.) that already scan for CP.

Re: The Problem with Perceptual Hashes

#53

Post by ohazi »

nine_k wrote: post #38
stickfigure wrote: post #10

I've also implemented perceptual hashing algorithms for use in the real world. Article is correct, there really is no way to eliminate false positives while still catching minor changes (say, resizing, cropping, or watermarking). I'm sure I'm not the only person with naked pictures of my wife. Do you really want a false positive to result in your intimate moments getting shared around some outsourced boiler room for…

Buy a subcompact camera. Never upload such photos to any cloud. Use your local NAS / external disk / your Linux laptop's encrypted hard drive. Unless you prefer to live dangerously, of course.

Consumer NAS boxes like the ones from Synology or QNAP have "we update your box at our whim" cloud software running on them and are effectively subject to the same risks, even if you try to turn off all of the cloud options. I probably wouldn't include a NAS on this list unless you built it yourself.

It looks like you've updated your comment to clarify Linux laptop's encrypted hard drive, and I agree with your line of thinking. Modern Windows and Mac OS are effectively cloud operating systems where more or less anything can be pushed at you at any time.

Re: The Problem with Perceptual Hashes

#54

Post by zxcvbn4038 »

stickfigure wrote: post #10

I've also implemented perceptual hashing algorithms for use in the real world. Article is correct, there really is no way to eliminate false positives while still catching minor changes (say, resizing, cropping, or watermarking). I'm sure I'm not the only person with naked pictures of my wife. Do you really want a false positive to result in your intimate moments getting shared around some outsourced boiler room for…

Rookie mistake.

Three rules to live by:

1) Always pay your taxes

2) Don’t talk to the police

3) Don’t take photographs with your clothes off

Re: The Problem with Perceptual Hashes

#55

Post by iratewizard »

enedil wrote: post #26
mjlee wrote: post #18

Earlier quoted context omitted.

> I'm sure I'm not the only person with naked pictures of my wife. I'm not completely convinced that says what you want it to.

Didn't she possibly have previous partners?

I don't even have nude photos of my wife. The only person who might would be the NSA contractor assigned to watch her.

Re: The Problem with Perceptual Hashes

#56

Post by derefr »

ohazi wrote: post #53
nine_k wrote: post #38

Earlier quoted context omitted.

Buy a subcompact camera. Never upload such photos to any cloud. Use your local NAS / external disk / your Linux laptop's encrypted hard drive. Unless you prefer to live dangerously, of course.

Consumer NAS boxes like the ones from Synology or QNAP have "we update your box at our whim" cloud software running on them and are effectively subject to the same risks, even if you try to turn off all of the cloud options. I probably wouldn't include a NAS on this list unless you built it yourself. It looks like you've updated your comment to clarify Linux laptop's encrypted hard drive, and I agree with your line o…

With Synology's DSM, at least, there's no "firmware" per se; it's just a regular Linux install that you have sudo(1) privileges on, so you can just SSH in and modify the OS as you please (e.g. removing/disabling the update service.)

Re: The Problem with Perceptual Hashes

#58

Post by josephcsible »

emodendroket wrote: post #34
rustybolt wrote: post #16

> an Apple employee will then look at your (flagged) pictures. This means that there will be people paid to look at child pornography and probably a lot of private nude pictures as well.

And what do you think the content moderation teams employed by Facebook, YouTube, et al. do all day?

They look at content that people actively and explicitly chose to share with wider audiences.

Re: The Problem with Perceptual Hashes

#59

Post by starkd »

The method Apple is using looks more like a cryptographic hash. That's entirely different (and more secure) than a perceptual hash.

From https://www.apple.com/child-safety/

"Before an image is stored in iCloud Photos, an on-device matching process is performed for that image against the known CSAM hashes. This matching process is powered by a cryptographic technology called private set intersection, which determines if there is a match without revealing the result. The device creates a cryptographic safety voucher that encodes the match result along with additional encrypted data about the image. This voucher is uploaded to iCloud Photos along with the image."

Elsewhere, it does explain the use of neuralhashes which I take to be the perceptual hash part of it.

I did some work on a similar attempt awhile back. I also have a way to store hashes and find similar images. Here's my blog post. I'm currently working on a full site.

http://starkdg.github.io/posts/concise-image-descriptor

Re: The Problem with Perceptual Hashes

#60

Post by jdavis703 »

vineyardmike wrote: post #29
stickfigure wrote: post #10

I've also implemented perceptual hashing algorithms for use in the real world. Article is correct, there really is no way to eliminate false positives while still catching minor changes (say, resizing, cropping, or watermarking). I'm sure I'm not the only person with naked pictures of my wife. Do you really want a false positive to result in your intimate moments getting shared around some outsourced boiler room for…

> Do you really want a false positive to result in your intimate moments getting shared around some outsourced boiler room for laughs? these people also have no incentive to find you innocent for innocent photos. If they err on the side of false-negative, they might find themselves at the wrong end of a criminal search ("why didn't you catch this"), but if they false-positive they at worse ruin a random person's life…

Even still this has to go to the FBI or other law enforcement agency, then it’s passed on to a prosecutor and finally a jury will evaluate. I have a tough time believing that false positives would slip through that many layers.

That isn’t to say CASM scanning or any other type of drag net is OK. But I’m not concerned about a perceptual hash ruining someone’s life, just like I’m not concerned about a botched millimeter wave scan ruining someone’s life for weapons possession.

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