6 ms·

Intentional false negatives are mostly irrelevant. If you want to store galleries of illegal material on your phone, there are much better ways to do it which d

Intentional false negatives are mostly irrelevant. If you want to store galleries of illegal material on your phone, there are much better ways to do it which don't involve them being visually mangled, even if only slightly. Intentional false positives require knowledge of a hash. And even that isn't enough to get a human to scan your image. You would need to acquire a library of A1 CSAM images/hashes. You would need to generate images which match both NeuralHash and the unspecified secondary hash algorithm which runs on Apple's cloud servers. And then you'd need to repeat this trick a sufficient number of times to trigger human review, at which point a few people (probably some minions in a developing country) get to look at the images for 1 second before pressing the "not CSAM" button and having the images sent to a technical team in Cupertino for analysis.

ClumsyPilot 5y ago
If both false positives and false negatives are irrelevant, then the whole system and argument is irrelevant.
- simondotau 5y ago
  Huh? False negatives and false positives are irrelevant with respect to the utility of the overall system. It means they don't render the system irrelevant. Intentional false negatives are irrelevant because catching 100% of CSAM was never stated as a goal of the system. And because it's just not realistic to expect to see any real-world use by CSAM aficionados. Anyone savvy enough to understand the principles behind hashing (and trust some command line tool downloaded from Github) is probably smart enough to have better places to store their child porn than an iCloud gallery. Intentional false positives are irrelevant because there are, depending how you count them, between two and six other layers which would need to be thwarted or exploited in order for intentional false positives in NeuralHash to result in any adverse outcome.
  - DeathArrow 5y ago
    >Intentional false negatives are irrelevant because catching 100% of CSAM was never stated as a goal of the system. And because it's just not realistic to expect to see any real-world use by CSAM aficionados. Anyone savvy enough to understand the principles behind hashing (and trust some command line tool downloaded from Github) is probably smart enough to have better places to store their child porn than an iCloud gallery. So if the purpose of the system is not to catch persons dealing with CP, what is the purpose? Breaking user's privacy? We have a history of evil intentions masked by fighting against CP, drugs, money laundry and crime in general.
    - emodendroket 5y ago
      There is pretty much no enforcement mechanism against any crime which we can expect to catch everyone. False positives get bounced out by the safeguards, false negatives wouldn't have been caught in the first place... that still presumably leaves a number of true positives who wouldn't have otherwise been caught.
    - kalleboo 5y ago
      Facebook is catching millions of CSAM images being directly uploaded by people to Facebook/Messenger of all places. There are still plenty of complete idiots trading CSAM that one could see value in apprehending.
      - simondotau 5y ago
        That's what boggles my mind. I really don't understand how someone could be trading in CSAM without knowing how dangerous it is to trade in CSAM.
        sokoloff 5y ago
        I believe there is an incredibly wide spectrum of most human qualities and traits. I see no reason to think that general intelligence, technical awareness, utility maximization, impulse control, or risk-reward calculation wouldn’t have similar distributions such that plenty of people would end up in a set prone to share risky material on such channels.
- maratc 5y ago
  To the contrary. A system that detects Covid-19 in infected people and doesn't detect it in healthy people, where the errors of both types (false positives and false negatives) are irrelevant, is not only relevant, it's a very well designed system.
joe_the_user 5y ago
Intentional false negatives are mostly irrelevant. If you want to store galleries of illegal material on your phone, there are much better ways to do it which don't involve them being visually mangled, even if only slightly. So, you're accepting that Apple's approach is useless for anyone who's "determined" but you still seem to be arguing there's some merit in this complex "architecture" of surveillance.
- simondotau 5y ago
  I disagree that it's useless. In fact I wouldn't be surprised if it's already been effective despite not being implemented yet. The announcement of an impending threat of scanning probably managed to get most CSAM afficinados to swear off iCloud already. And if so, it would be no small irony that the noisy criticism would have ensured that Apple was heard loud and clear by the CSAM community.
  - joe_the_user 5y ago
    I disagree that it's useless. In fact I wouldn't be surprised if it's already been effective despite not being implemented yet. The announcement of an impending threat of scanning probably managed to get most CSAM afficinados to swear off iCloud already. So the idea is that mass surveillance is great even if it's effect is scaring criminals while it actually only catches people at random? We've arrived at the opposite of the common reprise of law. No longer "It is Better that Ten Guilty Persons Go Free Than that One Innocent Person be Convicted" but "It is better that Ten Innocent Persons Be Dragooned Than that One Guilty Person Go Free"
    - simondotau 5y ago
      All I'm saying is that I understand why Apple doesn't want CSAM on their servers, while also reserving the ability to implement end to end encryption on photo galleries in future. It's a tough line for them to walk. Personally I don't see any substantial moral difference to what Apple was planning versus what Google and Facebook already do, aside for the somewhat icky aspect that some initial CPU cycles are occurring on hardware I own. I'm equally concerned that a purported need to scan for CSAM could be used by legislators as a way to convince the population that the Government needs more encryption backdoors. Personally I'd rather have my photos inconsequentially hashed than have encryption legislatively broken.
chmod775 5y ago
> Intentional false positives require knowledge of a hash. The code/network detecting this will be run on the client. So yes, a 'hash' or an equivalent will be known. You would have to hope that the secondary system is robust enough to not fall victim to the same manipulated image. And it really is on Apple to first prove it isn't.
- jdlshore 5y ago
  No, it is not. The hash is computed on the client, but hash comparison happens on the server, using some cryptographic magic that only reveals a “visual derivative” if enough images match. It’s fairly complex and I don’t recall the details, but the library of “bad” hashes is not accessible.
  - tsimionescu 5y ago
    No, the entire premise of NeuralHash is that no information about your pictures leaves your system unless it has been flagged as 'potentially CSAM'. NeuralHash itself is basically a DB of CSAM hashes encoded as an artificial neural network. In your example, each picture on your phone (that you are trying to upload to iCloud) would be hashed, and the hash would be sent to Apple. This is exactly the opposite of what they are promising with NeuralHash. Edit: I am almost entirely wrong, see the comment reply from krisoft. Apologies!
    - krisoft 5y ago
      > In your example, each picture on your phone (that you are trying to upload to iCloud) would be hashed, and the hash would be sent to Apple. This is exactly the opposite of what they are promising with NeuralHash. No. You are wrong. They do hash each image and they do upload the hash derived safety voucher always. Here is the Apple technical paper: https://www.apple.com/child-safety/pdf/CSAM_Detection_Technical_Summary.pdf https://www.apple.com/child-safety/pdf/CSAM_Detection_Techni... There is a fairly complicated cryptographic algorithm which, according to apple, lets them open the safety voucher only if there is a match with the database. The user devices only have a cryptographicaly blinded version of the hash database which they can’t turn back to real hashes without apple’s private key. This means that the plain neuralhashes are not available to the end users.
kf6nux 5y ago
The other reason why false negatives are mostly irrelevant is because the hash DB can be updated to include them, so the risk of storing them in iCloud remains the same.
- nullc 5y ago
  That doesn't fly. The encrypted list is stored on the devices for security and performance reasons: otherwise it would be too easy to ship people customized lists with arbitrary images. You can't just rapidly revise the list without undermining the privacy protection here. Also the space of modifications is gigantic, for any given image there should be millions of differently hash variations which can be reached without major visual damage. (at least for neuralhash the figure is billions)... so you can't just stick all of them in the database. You could stick widely circulating variations in the database, however... sure.
  - kf6nux 5y ago
    I'm honestly not sure what you're refuting here. Are you saying the hash DB can't be updated or that already uploaded photos won't be compared to hash updates?
    - nullc 5y ago
      The hashdb is part of the operating system and only gets updated with OS updates. It can be updated-- at some cost. But if it is very frequently updated then the protection against receiving a targeted list is lost. To state it another way: Users ask "Why won't the government order apple just gives me a list of the hash of every political image on the internet in order to expose my files?" and the answer is that the database is part of the OS, common to everyone, updated infrequently, so it can't be used in targeted attacks. That protection is lost if the database is frequently updated. It's also true that already uploaded photos won't be rescanned, but that wasn't the point I was trying to make.

ClumsyPilot 5y ago

If both false positives and false negatives are irrelevant, then the whole system and argument is irrelevant.

simondotau 5y ago
Huh? False negatives and false positives are irrelevant with respect to the utility of the overall system. It means they don't render the system irrelevant. Intentional false negatives are irrelevant because catching 100% of CSAM was never stated as a goal of the system. And because it's just not realistic to expect to see any real-world use by CSAM aficionados. Anyone savvy enough to understand the principles behind hashing (and trust some command line tool downloaded from Github) is probably smart enough to have better places to store their child porn than an iCloud gallery. Intentional false positives are irrelevant because there are, depending how you count them, between two and six other layers which would need to be thwarted or exploited in order for intentional false positives in NeuralHash to result in any adverse outcome.
- DeathArrow 5y ago
  >Intentional false negatives are irrelevant because catching 100% of CSAM was never stated as a goal of the system. And because it's just not realistic to expect to see any real-world use by CSAM aficionados. Anyone savvy enough to understand the principles behind hashing (and trust some command line tool downloaded from Github) is probably smart enough to have better places to store their child porn than an iCloud gallery. So if the purpose of the system is not to catch persons dealing with CP, what is the purpose? Breaking user's privacy? We have a history of evil intentions masked by fighting against CP, drugs, money laundry and crime in general.
  - emodendroket 5y ago
    There is pretty much no enforcement mechanism against any crime which we can expect to catch everyone. False positives get bounced out by the safeguards, false negatives wouldn't have been caught in the first place... that still presumably leaves a number of true positives who wouldn't have otherwise been caught.
  - kalleboo 5y ago
    Facebook is catching millions of CSAM images being directly uploaded by people to Facebook/Messenger of all places. There are still plenty of complete idiots trading CSAM that one could see value in apprehending.
    - simondotau 5y ago
      That's what boggles my mind. I really don't understand how someone could be trading in CSAM without knowing how dangerous it is to trade in CSAM.
      - sokoloff 5y ago
        I believe there is an incredibly wide spectrum of most human qualities and traits. I see no reason to think that general intelligence, technical awareness, utility maximization, impulse control, or risk-reward calculation wouldn’t have similar distributions such that plenty of people would end up in a set prone to share risky material on such channels.
maratc 5y ago
To the contrary. A system that detects Covid-19 in infected people and doesn't detect it in healthy people, where the errors of both types (false positives and false negatives) are irrelevant, is not only relevant, it's a very well designed system.

joe_the_user 5y ago

Intentional false negatives are mostly irrelevant. If you want to store galleries of illegal material on your phone, there are much better ways to do it which don't involve them being visually mangled, even if only slightly. So, you're accepting that Apple's approach is useless for anyone who's "determined" but you still seem to be arguing there's some merit in this complex "architecture" of surveillance.

simondotau 5y ago
I disagree that it's useless. In fact I wouldn't be surprised if it's already been effective despite not being implemented yet. The announcement of an impending threat of scanning probably managed to get most CSAM afficinados to swear off iCloud already. And if so, it would be no small irony that the noisy criticism would have ensured that Apple was heard loud and clear by the CSAM community.
- joe_the_user 5y ago
  I disagree that it's useless. In fact I wouldn't be surprised if it's already been effective despite not being implemented yet. The announcement of an impending threat of scanning probably managed to get most CSAM afficinados to swear off iCloud already. So the idea is that mass surveillance is great even if it's effect is scaring criminals while it actually only catches people at random? We've arrived at the opposite of the common reprise of law. No longer "It is Better that Ten Guilty Persons Go Free Than that One Innocent Person be Convicted" but "It is better that Ten Innocent Persons Be Dragooned Than that One Guilty Person Go Free"
  - simondotau 5y ago
    All I'm saying is that I understand why Apple doesn't want CSAM on their servers, while also reserving the ability to implement end to end encryption on photo galleries in future. It's a tough line for them to walk. Personally I don't see any substantial moral difference to what Apple was planning versus what Google and Facebook already do, aside for the somewhat icky aspect that some initial CPU cycles are occurring on hardware I own. I'm equally concerned that a purported need to scan for CSAM could be used by legislators as a way to convince the population that the Government needs more encryption backdoors. Personally I'd rather have my photos inconsequentially hashed than have encryption legislatively broken.

chmod775 5y ago

> Intentional false positives require knowledge of a hash. The code/network detecting this will be run on the client. So yes, a 'hash' or an equivalent will be known. You would have to hope that the secondary system is robust enough to not fall victim to the same manipulated image. And it really is on Apple to first prove it isn't.

jdlshore 5y ago
No, it is not. The hash is computed on the client, but hash comparison happens on the server, using some cryptographic magic that only reveals a “visual derivative” if enough images match. It’s fairly complex and I don’t recall the details, but the library of “bad” hashes is not accessible.
- tsimionescu 5y ago
  No, the entire premise of NeuralHash is that no information about your pictures leaves your system unless it has been flagged as 'potentially CSAM'. NeuralHash itself is basically a DB of CSAM hashes encoded as an artificial neural network. In your example, each picture on your phone (that you are trying to upload to iCloud) would be hashed, and the hash would be sent to Apple. This is exactly the opposite of what they are promising with NeuralHash. Edit: I am almost entirely wrong, see the comment reply from krisoft. Apologies!
  - krisoft 5y ago
    > In your example, each picture on your phone (that you are trying to upload to iCloud) would be hashed, and the hash would be sent to Apple. This is exactly the opposite of what they are promising with NeuralHash. No. You are wrong. They do hash each image and they do upload the hash derived safety voucher always. Here is the Apple technical paper: https://www.apple.com/child-safety/pdf/CSAM_Detection_Technical_Summary.pdf https://www.apple.com/child-safety/pdf/CSAM_Detection_Techni... There is a fairly complicated cryptographic algorithm which, according to apple, lets them open the safety voucher only if there is a match with the database. The user devices only have a cryptographicaly blinded version of the hash database which they can’t turn back to real hashes without apple’s private key. This means that the plain neuralhashes are not available to the end users.

kf6nux 5y ago

The other reason why false negatives are mostly irrelevant is because the hash DB can be updated to include them, so the risk of storing them in iCloud remains the same.

nullc 5y ago
That doesn't fly. The encrypted list is stored on the devices for security and performance reasons: otherwise it would be too easy to ship people customized lists with arbitrary images. You can't just rapidly revise the list without undermining the privacy protection here. Also the space of modifications is gigantic, for any given image there should be millions of differently hash variations which can be reached without major visual damage. (at least for neuralhash the figure is billions)... so you can't just stick all of them in the database. You could stick widely circulating variations in the database, however... sure.
- kf6nux 5y ago
  I'm honestly not sure what you're refuting here. Are you saying the hash DB can't be updated or that already uploaded photos won't be compared to hash updates?
  - nullc 5y ago
    The hashdb is part of the operating system and only gets updated with OS updates. It can be updated-- at some cost. But if it is very frequently updated then the protection against receiving a targeted list is lost. To state it another way: Users ask "Why won't the government order apple just gives me a list of the hash of every political image on the internet in order to expose my files?" and the answer is that the database is part of the OS, common to everyone, updated infrequently, so it can't be used in targeted attacks. That protection is lost if the database is frequently updated. It's also true that already uploaded photos won't be rescanned, but that wasn't the point I was trying to make.