Device #1 — Alice's laptop · acting
Creates its identity, is forced through backup enrollment, works normally — and is then destroyed.
Device #2 — the replacement · acting
A brand-new device with empty storage. Everything it recovers comes from the credential plus the server's opaque data.
Watch the identity key row: after step 5 the replacement holds the same one, which is what makes it the same member rather than a new one.
What happened — newest first
○Backup is mandatory: vault operations are unreachable until enrollment completes (spec §9.6)
○The recovery credential is system-generated, shown once, and never sent to the server (spec §9.6)
○The server stores only an opaque sealed blob; the KDF and its cost parameters travel with it (spec §6.2, §10.2)
○A wrong credential fails cryptographically — there is nothing to “reset” server-side (spec §13)
○Restore recovers the same device identity, and with it the same manager authority (spec §9.6)
○A backup made before the vault existed still recovers its full history, via the secret history chain (spec §9.7)