I would like Delta Chat to support account-based backup, recovery, and message synchronization.
Ideally, I could sign in on a new device with a username and password and restore my existing profile—including my cryptographic identity, contacts, groups, chat history, and attachments—without needing access to an old device or manually transferring a backup.
After signing in, messages and changes such as read status, edits, and deletions should stay synchronized across my devices.
This should preserve end-to-end encryption. Profile data and private keys should be encrypted on the client before being uploaded, so the relay or backup server cannot read them. If secure recovery requires a separate recovery key or passphrase, that would be acceptable.
I run my own Chatmail server and NAS, and I would like the option to store these encrypted backups on infrastructure I control.