Then 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.
alt Hacker News
Then 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.