Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The Problem with Perceptual Hashes

rentafounder.com

Post reply on HN
Print view View original

201–210 of 440 posts

Re: The Problem with Perceptual Hashes

#201

Post by bzha »

macintux wrote: post #190
dannyw wrote: post #172

Earlier quoted context omitted.

Did you literally not see a former president effectively get silenced in the public sphere by 3 corporations? How can you seriously believe that these corporations (who are not subject to the first amendment, and cannot be challenged in court) won't extend and abuse this technology to tackle "domestic extremism" but broadly covering political views?

> a former president effectively get silenced in the public sphere It's laughable that a man who can call a press conference at a moment's notice and get news coverage for anything he says can be "silenced" because private companies no longer choose to promote his garbage.

This is akin to saying rich people have lots of money, so why not steal from them.

Re: The Problem with Perceptual Hashes

#202

Post by 0x426577617265 »

seph-reed wrote: post #81
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…

Someone is going to figure out how to make false positives, and then an entire genre of meme will be born from putting regular memes through a false positive machine, just for the lulz. Someone else could find a way to make every single possible mutation of false positive Goatse/Lemonparty/TubGirl/etc. Then some poor Apple employee has to check those out.

If the process of identifying the images is done on the device, then a jailbroken device will likely give an attacker access to the entire DB. I'm not sure how useful it would be, but if the attacker did have access to actual known CSAM images it probably wouldn't be hard for them to produce false positives and test it against the DB on the jailbroken device, without notifying the company.

Re: The Problem with Perceptual Hashes

#203

Post by visarga »

Klonoar wrote: post #120
coldtea wrote: post #119

Earlier quoted context omitted.

> I would really like people to start answering this: what exactly do you think has changed? e.g, Apple has announced they'll be doing this check? What exactly do you think is the same as before? > The exact same outcome can happen regardless of whether it's done on or off device. iCloud has _always_ been a known vector for authorities to peek. That's neither here, nor there. It's another thing to peak selectively wi…

>What exactly do you think is the same as before? The same checking when you synced things to iCloud. As has been repeated over and over again, this check happens for iCloud Photos. It's not running arbitrarily. Your photos were compared before and they're being compared now... if you're using iCloud Photos.

It's not the same because before the hashing was done in the cloud, but now the model is accessible locally, you just need to take pictures. This means it's easier to hack.

If someone discovers a way to reliably generate adversarial images they can send such images to someone else to iSWAT them.

Re: The Problem with Perceptual Hashes

#204

Post by visarga »

Klonoar wrote: post #134
coldtea wrote: post #128

Earlier quoted context omitted.

> The same checking when you synced things to iCloud. As has been repeated over and over again, this check happens for iCloud Photos. It's not running arbitrarily. Who said it's running "arbitrarily"? Who said it's not about iCloud Photos? > Your photos were compared before and they're being compared now... if you're using iCloud Photos. They weren't always compared, they started being compared a few years ago, and t…

>Both are bad, and not the responsibility of a company selling phones Apple is not just a hardware company and there is no obligation for them to host offending contents on their servers - just as Dropbox, Google, and so on would maintain with theirs. >As for your suggestions to just "stop using iCloud Photos", how about we get to enjoy the features we bought our devices for, without stuff we didn't ask for and don't…

With many more images, many more false positives. One has as a consequence a message or account being deleted, the other - being reported to the police. Very different!

Re: The Problem with Perceptual Hashes

#205

Post by andy_ppp »

bzha wrote: post #201
macintux wrote: post #190

Earlier quoted context omitted.

> a former president effectively get silenced in the public sphere It's laughable that a man who can call a press conference at a moment's notice and get news coverage for anything he says can be "silenced" because private companies no longer choose to promote his garbage.

This is akin to saying rich people have lots of money, so why not steal from them.

Well, I prefer to think of this as redistribution rather than theft. When the government pass laws to tax rich people more I think that’s good!

Re: The Problem with Perceptual Hashes

#206

Post by cratermoon »

If I'm reading this right? Apple is saying they are going to flag CSAM they find on their servers. This article talks about finding a match for photos by comparing a hash of a photo you're testing with a hash you have, from a photo you have.

Does this mean Apple had/has CSAM available to generate the hashes?

Re: The Problem with Perceptual Hashes

#207

Post by etchalon »

Klonoar wrote: post #129
coldtea wrote: post #119

Earlier quoted context omitted.

> I would really like people to start answering this: what exactly do you think has changed? e.g, Apple has announced they'll be doing this check? What exactly do you think is the same as before? > The exact same outcome can happen regardless of whether it's done on or off device. iCloud has _always_ been a known vector for authorities to peek. That's neither here, nor there. It's another thing to peak selectively wi…

Responding in a separate comment since I either missed the second half, or it was edited in. >That's neither here, nor there. It's another thing to peak selectively with a warrant of sorts, than to (a) peak automatically in everybody, (b) with a false-positive-prone technique, especially since the mere accusation on a false match can be disastrous for a person, even if they eventually are proven innocent... I do not…

I'm incredibly amused by the number of supposedly deeply technical and informed people on this site who seem to be unaware of CSAM scanning and its existing use on cloud services.

Re: The Problem with Perceptual Hashes

#208

Post by [deleted] »

cratermoon wrote: post #206

If I'm reading this right? Apple is saying they are going to flag CSAM they find on their servers. This article talks about finding a match for photos by comparing a hash of a photo you're testing with a hash you have, from a photo you have. Does this mean Apple had/has CSAM available to generate the hashes?

[deleted]

Re: The Problem with Perceptual Hashes

#209

Post by visarga »

dannyw wrote: post #176
Klonoar wrote: post #137

Earlier quoted context omitted.

This example changes with regards to emotional weight if you remove "a man" and leave it at just "a scanning machine". There is no human scanning your photos on an iPhone, so let's compares apples to apples here. If that scanning machine didn't reveal the contents of my mail, and then ensured that it wasn't able to be given out in-transit? Yeah, I'd potentially be fine with it - but I'll leave this answer as a hypoth…

There actually is a man involved: enough similarities and a human will review the photos. Every algorithm, especially perceptual hashing, will have false positives, and at Apple's scale, some people's private and intimate photos will be false positives and be exposed to a man looking at it.

> some people's private and intimate photos will be false positives and be exposed to a man looking at it

and deciding who gets reported to police based on their cultural views on nudity

Re: The Problem with Perceptual Hashes

#210

Post by thaumasiotes »

exporectomy wrote: post #152
thaumasiotes wrote: post #148

Earlier quoted context omitted.

> like the dogs which conveniently bark at police's secret hand sign This isn't necessary; the state of the art is for drug dogs to alert 100% of the time. They're graded on whether they ever miss drugs. It's easy to never miss.

Airport baggage drug dogs must obviously have far fewer false positives than that. So alerting on everything can't be the state of the art.

https://reason.com/2021/05/13/the-police-dog-who-cried-drugs...

> Similar patterns abound nationwide, suggesting that Karma's career was not unusual. Lex, a drug detection dog in Illinois, alerted for narcotics 93 percent of the time during roadside sniffs, but was wrong in more than 40 percent of cases. Sella, a drug detection dog in Florida, gave false alerts 53 percent of the time. Bono, a drug detection dog in Virginia, incorrectly indicated the presence of drugs 74 percent of the time.

Post reply on HN