A Sync Master Key (SMK) wraps event bundles and checkpoints. The SMK is itself wrapped in one or more slots:
- Recovery key:
bech32remnix1..., shown once at setup, never stored on the remote - FIDO2
hmac-secret(USB HID; NFC is not used) - YubiKey PIV
Generation manifests are HMAC-signed with a key derived from the SMK. metadata/manifest is also signed. Tampered JSON fails verification and is
not applied.
Key rotation (remnix key rotate) creates seq+1 and retains the previous
generation so older bundles still decrypt. A generation is not considered
active until the authenticated metadata/manifest selects it. Rotation is
retry-safe: if a storage or local-state error interrupts the operation,
rerunning the command reconciles any in-progress rotation instead of blindly
creating another generation. Rerun remnix key rotate after an interrupted
attempt rather than editing generation files. remnix key recover remains the
path for genuine fork or corruption states, not ordinary transient failures.
Old generations stay until garbage collection can prove they are no longer
referenced.
Running setup twice produces two generations that both claim seq=1 -
recover with remnix key recover.
The daemon cannot prompt for FIDO every minute. Unlock once per session; the OS keyring holds the SMK.
Remote storage is untrusted: confidentiality depends on the SMK remaining secret, not on the cloud provider’s access controls.