4 ms·
They wouldn't have a human look at it. They don't have the images, only the hashes–that's the point. And it's somewhat irrelevant how the probability of collis
by IfOnlyYouKnew 5y ago
They wouldn't have a human look at it. They don't have the images, only the hashes–that's the point.
And it's somewhat irrelevant how the probability of collisions is specifically calulated (1/1000 already assumed 1:n comparisons), as long as we agree it's easy to calculate for a given user. The algorithm does know about the sizes of the respective image libraries, for example, and could adjust the threshold with precision.
- Someone 5y agoThey don’t have the images, but they do have “visual derivatives”. https://www.apple.com/child-safety/pdf/CSAM_Detection_Technical_Summary.pdf https://www.apple.com/child-safety/pdf/CSAM_Detection_Techni...: “The device creates a cryptographic safety voucher that encodes the match result. It also encrypts the image’s NeuralHash and a visual derivative. This voucher is uploaded to iCloud Photos along with the image. […] Once more than a threshold number of matches has occurred, Apple has enough shares that the server can combine the shares it has retrieved, and reconstruct the decryption key for the ciphertexts it has collected, thereby revealing the NeuralHash and visual derivative for the known CSAM matches.” https://www.apple.com/child-safety/pdf/Security_Threat_Model_Review_of_Apple_Child_Safety_Features.pdf https://www.apple.com/child-safety/pdf/Security_Threat_Model... is even clearer: “The decrypted vouchers allow Apple servers to access a visual derivative – such as a low-resolution version – of each matching image. These visual derivatives are then examined by human reviewers”