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Custody
Where signing keys live. Software custody today, hardware as an option later.
What Custody is
A separate service, in its own process with its own database and its own credentials, holding two classes of key: per-principal Ed25519 approval keys, and per-organization secp256k1 chain signing keys.
It accepts a semantic operation and builds what it signs itself. There is no field on the wire for a sign document, a digest, raw bytes or a type URL — so no caller, including a fully compromised Gateway, can hand it something to sign.
Custody is not authorization
Custody being down does not stop authorization or execution. It is reached only at the signing boundary, which is where an approval ceremony completes.
Deployment
- Reachable only over mutual TLS, from a client whose certificate name is on an allow-list.
- Read-only root filesystem, every Linux capability dropped, no privileged mode, no Docker socket, no host device.
- No published port — it is reachable on an internal network and nowhere else.
- Keys are encrypted at rest with AES-256-GCM under a per-key DEK, wrapped by a KEK injected as a secret and never stored in the data volume.