After my other post I'm looking over some other possibilities to do what I'm trying to do. How To Recover End-To-End Encrypted Data After Losing Private Key?

If I save user data in server, in order to restore the data I should have the key to unlock the encryption which is not safe. If I don't have the key then I cant decrypt the restored data.

From some comments and posts I read, I can store all the data in local and Google Drive, iCloud can backup the app data for me. I don't know how that works, if someone can explain the steps that would be nice.

Even though I can backup the data in Google Drive or iCloud, how can I use multiple devices at the same time with accessing the same data which is saved in local or backed up in drive? For example, Facebook messenger, WhatsApp etc. (mobile app and web browser at the same time) I might try to share the data with a shared key or QR code or something but I don't know how effective it would be.

  • Use Google Drive API. Backups aren't meant for multi-device support because they aren't as recent as new messages. You have to share data from the main device like WhatsApp web does. Signal simply starts from fresh on multi-device.
    – defalt
    Commented Feb 22, 2021 at 10:36
  • @defalt so to make it like whatsapp i should share local data to new device? And if i do it like signal that means i cant access to old messages, only new ones right?
    – Eagleclaw
    Commented Feb 22, 2021 at 10:57
  • Yes. WhatsApp web requires host device to be online while Signal allows devices to work asynchronously. If you want chats on all devices, make most recent backup at the time of adding another device and restore it on that device.
    – defalt
    Commented Feb 22, 2021 at 11:26


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