alt Hacker NewsThen the app can make a bog-standard encrypted-at-rest backup to somewhere and make all the computations on the device on the cleartext data.
I don't see the need to do computations on the encrypted data here, which is what FHE would provide in addition to traditional encryption.
> and don't have access to the account anymore.
This would be trouble with or without FHE. Even if the backend wouldn't need to decrypt the data, the user will - so as soon as you actually want to show something in the app, you have the same key management problems as without FHE.
Okay, so the platform becomes valuable to its users when it's able to suggest things like "based on millions of users, people with cycles like yours typically ovulate around day 16."
In order to do the data mining in order to make those kinds of claims, traditionally you'd need to have access to the data.
As you point out, encrypted-at-rest is solved. But what about when it's not at rest?
In-use and in-transit is when FHE kicks in. Sure, you could just do it locally, but then you miss out on the aggregate data mining. Not for advertisers, but because it helps women with their bodies. The compelling product claim is "we literally cannot read your period data." Not "we pinky swear not to" but "we actually really really actually can't!"