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The Problem with Perceptual Hashes

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Re: The Problem with Perceptual Hashes

#371

Post by voidnullnil »

asimpletune wrote: post #105
mrtksn wrote: post #72

The technical challenges aside, I’m very disturbed that my device will be reporting me to the authorities. That’s very different from authorities taking a sneak peek into my stuff. That’s like the theological concept of always being watched. It starts with child pornography but the technology is indifferent towards it, it can be anything. It’s always about the children because we all want to save the children. Soon t…

I have been a big Apple fan ever since my first computer. This is the first time I legitimately thought I need to start thinking about something else. It’s kind of sad.

Companies change. The sad part is, there is no next company to move to.

Re: The Problem with Perceptual Hashes

#372

Post by yellow_lead »

wilg wrote: post #180
yellow_lead wrote: post #61

Regarding false positives re:Apple, the Ars Technica article claims > Apple offers technical details, claims 1-in-1 trillion chance of false positives. There are two ways to read this, but I'm assuming it means, for each scan, there is a 1-in-1 trillion chance of a false positive. Apple has over 1 billion devices. Assuming ten scans per device per day, you would reach one trillion scans in ~100 days. Okay, but not al…

Apple claims that metric for a false positive account flagging, not photo matching. > The threshold is set to provide an extremely high level of accuracy and ensures less than a one in one trillion chance per year of incorrectly flagging a given account. https://www.apple.com/child-safety/

Good find

Re: The Problem with Perceptual Hashes

#373

Post by wpietri »

l33t2328 wrote: post #298
visarga wrote: post #199

Earlier quoted context omitted.

Yes, because we all trust him at this point /s

You don’t have to believe him; it’s clear on the face of it. Trump often spoke directly to the voters on Twitter and Youtube. That’s gone now.

Trump can still speak directly to the voters who are interested. It turns out not very many are interested. E.g.: https://www.cnbc.com/2021/06/02/trump-blog-page-shuts-down-f...

Even Fox has stopped running his events: https://deadline.com/2021/06/donald-trump-rally-networks-ski...

The largest pro-Trump network has seen major declines in ratings: https://www.thewrap.com/newsmax-fox-news-six-months-ratings/

Re: The Problem with Perceptual Hashes

#374

Post by wpietri »

feanaro wrote: post #249
gpm wrote: post #156

Earlier quoted context omitted.

With you up to here, but this is jumping the shark > I bet you, after the next election in the US your device will be reporting you for spreading far right or deep state lies, depending on who wins. The US is becoming less stable, sure [1], but there is still a very strong culture of free speech, particularly political speech. I put the odds that your device will be reporting on that within 4 years as approximately 0…

> but there is still a very strong culture of free speech, particularly political speech. Free speech didn't seem so important recently when the SJW crowd started mandating to censor certain words because they're offensive.

Free speech doesn't mean the speaker is immune from criticism or social consequences. If I call you a bunch of offensive names here, I'll get downvoted for sure. The comment might be hidden from most. I might get shadowbanned or totally banned, too.

That was true of private spaces long before HN existed. If you're a jerk at a party, you might get thrown out. I'm sure that's been true as long as there have been parties.

The only thing "the SJW crowd" has changed is which words are now seen as offensive.

Re: The Problem with Perceptual Hashes

#376

Post by marcellus23 »

tjoff wrote: post #337
marcellus23 wrote: post #333

Earlier quoted context omitted.

But what’s the practical difference between scanning photos when they’re uploaded to iCloud on a server, or on device?

A world of difference. Both in practical terms and principle. To start, once you upload something to the cloud you do - or at least are expected to - realize that it is under full control of another entity. Because of that you might not use iCloud or you might not upload everything to iCloud.

I think you might still be confused? Only photos being uploaded to iCloud are scanned. So users can still choose not to use iCloud and avoid this.

I certainly hope you didn’t get yourself all worked up without actually understanding what you’re mad at :)

Re: The Problem with Perceptual Hashes

#377

Post by ATsch »

jokoon wrote: post #244
ezoe wrote: post #110

The problem of hash or NN based matching is, the authority can avoid explaining the mismatch. Suppose the authority want to false-arrest you. They prepare a hash that matches to an innocent image they knew the target has in his Apple product. They hand that hash to the Apple, claiming it's a hash from a child abuse image and demand privacy-invasive searching for the greater good. Then, Apple report you have a file th…

> Suppose the authority want to false-arrest you. Why would they want that?

This is a pretty weird question considering the mountains of documentation of authorities doing just that. This is not some kind of hypothetical that needs extraordinary justification.

Re: The Problem with Perceptual Hashes

#378

Post by [deleted] »

marcellus23 wrote: post #376
tjoff wrote: post #337

Earlier quoted context omitted.

A world of difference. Both in practical terms and principle. To start, once you upload something to the cloud you do - or at least are expected to - realize that it is under full control of another entity. Because of that you might not use iCloud or you might not upload everything to iCloud.

I think you might still be confused? Only photos being uploaded to iCloud are scanned. So users can still choose not to use iCloud and avoid this. I certainly hope you didn’t get yourself all worked up without actually understanding what you’re mad at :)

[deleted]

Re: The Problem with Perceptual Hashes

#379

Post by 7373737373 »

nonbirithm wrote: post #369
7373737373 wrote: post #108

Earlier quoted context omitted.

I, too, have worked on similar detection technology using state of the art neural networks. There is no way there won't be false positives, I suspect many, many more than true positives. It is very likely that as a result of this, thousands of innocent people will have their most private of images viewed by unaccountable strangers, will be wrongly suspected or even tried and sentenced. This includes children, teenage…

Microsoft, Facebook, Google and Apple have scanned data stored on their servers for CSAM for over a decade already. The difference is that Apple is moving the scan on-device. Has there been any report of even a single person who's been a victim of a PhotoDNA false positive in those ten years? I'm not trying to wave away the concerns about on-device privacy, but I'd want evidence that a such significant scale of wrong…

> I'm not seeing how a conviction can be made on the basis of a perceptual hash alone without the actual CSAM

This is a good point, but it's not just about people getting wrongly convicted, this system even introducing a remote possibility of having strangers view your personal files is disturbing. In the US, it violates the 4th amendment against unreasonable search, a company being the middleman doesn't change that. Privacy is a shield of the individual, here the presumption of innocence is deposed even before the trial. An extremely low false positive rate or the perceived harmlessness of the current government don't matter, the systems' existence is inherently wrong. It's an extension of the warrantless surveillance culture modern nations are already so good at.

"It is better that ten guilty persons escape than that one innocent suffer." - https://en.wikipedia.org/wiki/Blackstone%27s_ratio

In a future with brain-computer interfaces, would you like such an algorithm to search your mind for illegal information too?

Is it still your device if it acts against you?

Re: The Problem with Perceptual Hashes

#380

Post by wizzwizz4 »

wpietri wrote: post #366
zekrioca wrote: post #343

Earlier quoted context omitted.

You answered your own question and still don’t get it.

Then perhaps you could explain it? I also don't understand why server-side versus client-side CSAM inspection makes a big difference.

If I ask you to store my images, and you therefore have access to the images, you can scan them for stuff using your computers. The scope is limited to the images I ask you to store, and your computers are doing what you ask them to.

If you reprogram my computer to scan my images stored on my computer… different thing entirely. I don't have a problem with checking them for child abuse (in fact, I'd give up quite a bit of freedom to stop that), but nothing about this tech makes it specific to child abuse. I don't want my computer ratting me out for stuff that I have the right (or, possibly, the obligation) to be doing, just because the powerful don't want me doing it. At the moment, it doesn't.

This tech makes Apple-controlled computers untrustworthy. It will probably lead to the deaths of political dissidents; these things always do. Is that worth it?

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