4 ms·

In a certain sense it is cryptographic because the original CSAM images remains secret. While the hash is not useful for maintaining integrity it still provides

In a certain sense it is cryptographic because the original CSAM images remains secret. While the hash is not useful for maintaining integrity it still provides confidentiality. Edit: this is apparently not true as demonstrated by researchers.

judge2020 5y ago
This has technically been proven false: > Microsoft says that the "PhotoDNA hash is not reversible". That's not true. PhotoDNA hashes can be projected into a 26x26 grayscale image that is only a little blurry. 26x26 is larger than most desktop icons; it's enough detail to recognize people and objects. Reversing a PhotoDNA hash is no more complicated than solving a 26x26 Sudoku puzzle; a task well-suited for computers. https://www.hackerfactor.com/blog/index.php?/archives/929-One-Bad-Apple.html#:~:text=I%20have%20a%20whitepaper,possession%20of%20child%20pornography https://www.hackerfactor.com/blog/index.php?/archives/929-On...
- robertoandred 5y ago
  PhotoDNA and NeuralHash are not the same thing.
  - judge2020 5y ago
    Apple is using a private perceptual hash on the backend, likely to further filter out bad/spam tickets. https://twitter.com/fayfiftynine/status/1427899951120490497?s=21 https://twitter.com/fayfiftynine/status/1427899951120490497?... Given neuralhash is a hash of a hash, I imagine they’re running photodna and not some custom solution which would require Apple ingesting and hasing all of the images themselves using another custom perceptual hash system. > . Instead of scanning images in the cloud, the system performs on-device matching using a database of known CSAM image hashes provided by NCMEC and other child-safety organizations. Apple further transforms this database into an unreadable set of hashes, which is securely stored on users’ devices. https://www.apple.com/child-safety/pdf/CSAM_Detection_Technical_Summary.pdf#page=4 https://www.apple.com/child-safety/pdf/CSAM_Detection_Techni...
    - robertoandred 5y ago
      My reading of that is NCMEC provides NeuralHash hashes of their CSAM library to Apple, and Apple encrypts and blinds that database before storing it on devices.

judge2020 5y ago

This has technically been proven false: > Microsoft says that the "PhotoDNA hash is not reversible". That's not true. PhotoDNA hashes can be projected into a 26x26 grayscale image that is only a little blurry. 26x26 is larger than most desktop icons; it's enough detail to recognize people and objects. Reversing a PhotoDNA hash is no more complicated than solving a 26x26 Sudoku puzzle; a task well-suited for computers. https://www.hackerfactor.com/blog/index.php?/archives/929-One-Bad-Apple.html#:~:text=I%20have%20a%20whitepaper,possession%20of%20child%20pornography https://www.hackerfactor.com/blog/index.php?/archives/929-On...

robertoandred 5y ago
PhotoDNA and NeuralHash are not the same thing.
- judge2020 5y ago
  Apple is using a private perceptual hash on the backend, likely to further filter out bad/spam tickets. https://twitter.com/fayfiftynine/status/1427899951120490497?s=21 https://twitter.com/fayfiftynine/status/1427899951120490497?... Given neuralhash is a hash of a hash, I imagine they’re running photodna and not some custom solution which would require Apple ingesting and hasing all of the images themselves using another custom perceptual hash system. > . Instead of scanning images in the cloud, the system performs on-device matching using a database of known CSAM image hashes provided by NCMEC and other child-safety organizations. Apple further transforms this database into an unreadable set of hashes, which is securely stored on users’ devices. https://www.apple.com/child-safety/pdf/CSAM_Detection_Technical_Summary.pdf#page=4 https://www.apple.com/child-safety/pdf/CSAM_Detection_Techni...
  - robertoandred 5y ago
    My reading of that is NCMEC provides NeuralHash hashes of their CSAM library to Apple, and Apple encrypts and blinds that database before storing it on devices.