ncw96

I don’t believe Apple has said whether or not they send them in their initial referral to NCMEC, but law enforcement could easily get a warrant for them. iCloud Photos are encrypted at rest, but Apple has the keys.

(Many have speculated that this CSAM local scanning feature is a precursor to Apple introducing full end-to-end encryption for all of iCloud. We’ll see.)

Comment · 5 years ago

Apple has outlined[1] multiple levels of protection in place for this:

1. You have to reach a threshold of matches before your account is flagged.

2. Once the threshold is reached, the matched images are checked against a different perceptual hash algorithm on Apple servers. This means an adversarial image would have to trigger a collision on two distinct hashing algorithms.

3. If both hash algorithms show a match, then “visual derivative” (low-res versions) of the images are inspected by Apple to confirm they are CSAM.

Only after these three criteria are met is your account disabled and referred to NCMEC. NCMEC will then do their own review of the flagged images and refer to law enforcement if necessary.

[1]: https://www.apple.com/child-safety/pdf/Security_Threat_Model...

Comment · 5 years ago

Apple has said this is not the final version of the hashing algorithm they will be using: https://www.vice.com/en/article/wx5yzq/apple-defends-its-ant...

The Melodies of Subways Around the World nytimes.com

1 ncw96 5 years ago 0 comments

Comment · 5 years ago

You are correct — most of the iCloud data is not end-to-end encrypted. Apple discusses which data is end-to-end encrypted at https://support.apple.com/en-us/HT202303

Comment · 5 years ago

> As far as this is concerned, seems like if you don’t use iMessage or iCloud you’re safe for now.

Yes, this is correct. The Messages feature only applies to children under 18 who are in an iCloud Family, and the photo library feature only applies if you are using iCloud Photos.

Comment · 5 years ago

Sorry for the confusion — I was referring to just the CSAM hash feature that uploads results to iCloud.

There is also scanning for nudity in the Messages app, but those scans happen on-device and the photos stay on-device even if nudity is detected.

Comment · 5 years ago

A summary of the photo scanning system:

- Only applies to photos uploaded to iCloud

- Matching against a known set of CSAM (Child Sexual Abuse Material) hashes occurs on-device (as opposed to the on-server matching done by many other providers)

- Multiple matches (unspecified threshold) are required to trigger a manual review of matched photos and potential account suspension