The root-of-trust (RoT) signing key is the single anchor of the secure-boot chain: scripts/secrets/rot_sign.py sign signs every launched image with the private key, and the device trusts only images that verify against the public key provisioned into libs/ra8_dfu/src/ra8_rot.c (s_rot_root_pubkey). Lose the private key and no new image can be signed for the provisioned public key – you must re-key and re-flash.
The key is a NIST P-256 (ECDSA) keypair. The private key never enters git; it lives at ~/ra8d2-rot-signing-key.pem (0600) and, for durability + history, in a key store (below).
Key store: two backends
scripts/secrets/rot_keystore.py keeps a versioned, tagged history of every RoT key so you can create new credentials whenever you want and still recover any prior key. It picks a backend automatically (override with --backend):
| Backend | What it is | For whom |
|---|---|---|
| openbao | The team OpenBao server you already run (the k3s pod at BAO_ADDR), KV v2 with native versioning. Reached over HTTP by scripts/secrets/openbao_client.py – nothing is spun up locally. | Maintainers with vault access. |
| local | A 0700 directory (RA8_ROT_STORE_DIR, default ~/.config/ra8/rot) holding one PEM per version plus history.json. | Anyone who clones the repo – no OpenBao needed, same spirit as the .env fallback. |
auto uses OpenBao when it is configured and reachable, else falls back to the local store. Every stored version is tagged with the public key's SHA-256 fingerprint, its algorithm, when and at which commit it was created, and a free-text note.
OpenBao configuration
The vault address + AppRole identity come from the same 0600 creds file the HIL tooling uses – ~/.config/hil/openbao.env (override with HIL_OPENBAO_ENV); it holds how to reach the vault, never the secrets themselves. See scripts/secrets/openbao_client.py for the full key list. The RoT-specific path is BAO_ROT_SECRET_PATH (default ra8d2/rot-signing-key) under BAO_KV_MOUNT.
The AppRole policy must allow create/update/read on <mount>/data/ra8d2/rot-signing-key and <mount>/metadata/ra8d2/rot-signing-key.
Common operations
/bin/bash -p scripts/secrets/rot_provision.sh runs the first-time ceremony: generate a keypair, patch the public half into the firmware, store the private half. Everything afterwards goes through scripts/secrets/rot_keystore.py – storing a key as a new version, listing the history and its tags, reporting which backend is live, recovering an old version, and re-keying. Signing an image is scripts/secrets/rot_sign.py sign. Both take --help, which is the authority on their arguments.
rekey never loses a key: it stores the outgoing working key first, so the history always contains every key you have ever used. After a re-key the device must be re-flashed, because the provisioned public key changed.
Where this sits in the security cluster, and what it couples to:
