Comment by sgammon

> I'm only aware that apple offers advanced protection on your uploaded data, which you have to opt into, which might be what you're talking about...?

This is to store your data within iCloud. You can turn it off or on at your convenience, but end-to-end encryption prevents other features, which is why they leave the decision up to users.

In contrast, the article linked here does not involve your actual data leaving your device in any way. Even the metadata is encrypted and hashed and then compared in obfuscated form. Homomorphic encryption allows these computations to take place _on the encrypted form of the data_, _without_ revealing the results. Only you can make sense of the result.

Thus, data can be exchanged with a foreign computer while provably keeping your _actual_ data safe, since the computation was performed on an obfuscated form of it. Apple can't even track you down to gain your device's cooperation in decoding it, since you are hidden behind a proxy.