key-management.md

Key management

The device currently has one embedded Ed25519 verification key. The matching private seed is not part of the repository. tools/key_management.py provides non-overwriting generation and public fingerprint inspection.

Current embedded public-key fingerprint (SHA-256 over the raw 32-byte key):

482dd9daac3d406f779995a50a00eb2ac9948eb412cba4403e2f81091780499a

Class	Use	Committed private material	Production use
CI test	automated parser/signature tests	never	No
developer test	local images	never	No
research device	reversible lab board	never	No
production-like offline	ceremony rehearsal	never	only after review

python3 tools/key_management.py generate \
  --purpose research-device \
  --seed /secure/lab/stm32-research.seed \
  --public-header /secure/lab/research-public-key.h
python3 tools/key_management.py inspect --seed /secure/lab/stm32-research.seed

Seed paths must be mode 0600 and existing files are refused. The tool emits only the public key and its SHA-256 fingerprint. update_package.py build derives the public key in memory, adds the fingerprint to its build report, and immediately verifies the generated package. The seed is never in a package, manifest, UART frame, or log.

Before a device update, compare the fingerprint against the embedded header and release manifest. Keep at least two encrypted offline backups under separate control, with fingerprint, purpose, creation record, and test/production classification.

No in-field key rotation or revocation is implemented. See the ADR and the key-loss response. This is deliberate: a second key manifest without a hardware monotonic counter would increase brick and rollback risk.