SapwoodOpen-Source Key Management Tool for Heartwood Devices

What Sapwood Does Within the Heartwood Ecosystem

Sapwood is a companion application rather than a standalone wallet. Heartwood is the device side, and Sapwood is the interface you use to inspect and administer it. Think of it as a control panel: it shows what the device holds and lets you adjust how it responds to requests.

Because the device is the place where keys live, the software you use to manage it matters less for storage than for administration. Sapwood focuses on provisioning, policy and recovery tasks, which are the operations you need when you set up or maintain a device over months or years.

How Remote Management Works Without a Cloud Account

Sapwood uses two different connection methods. For first-time setup and recovery, it talks to the device directly over USB using the Web Serial API. For day-to-day administration, it sends authenticated, encrypted management events through Nostr relays. The device connects outward over WiFi, so it never opens an inbound port, and no cloud account or hosted management server sits in the middle.

This design has a practical consequence: you can manage a device from elsewhere on the internet as long as both the device and your controlling software can reach relays. It also means you need to keep your management credentials safe, because they are what authorizes changes.

Who Sapwood Is For

Sapwood suits developers building signing workflows on Heartwood hardware, technically confident hobbyists who want to understand their setup, and anyone evaluating open-source tools for key management. The interface assumes you are comfortable with concepts such as master slots, npubs, and client policies.

It is less suitable for someone who wants a turnkey experience with polished guides and customer support. Given the alpha status of the release, plan to test on a non-production device first and keep backups of any configuration you care about.

Key Concepts Behind the Interface

Several terms appear throughout the software. An npub is the public identifier used in the Nostr protocol, so a master slot's npub tells you which public identity the device presents. A derivation mode describes how keys are derived from a root secret; choosing or checking the mode matters because it determines whether two setups produce compatible keys.

Client policies define what a given client is allowed to request. Keeping policies narrow, one client at a time, reduces the impact if a single client is compromised. The operator credential is the authority that changes these settings, which is why Sapwood keeps it separate and offers a protected way to move it to a phone.

Typical Scenarios for Sapwood

A common use is provisioning a new device: connect it over USB, confirm its state, and then move to remote management so you can adjust policies without keeping the cable attached. Another is a recovery scenario, where the network path is down and you need to rotate the management operator or reset credentials physically at the device.

Developers testing integrations can use the live log view to watch firmware output while they send test requests. Operators who manage several clients can use the client list to audit who has access and revoke permissions that are no longer needed.

Supported coins

The documentation mentions Polygon and Nostr as networks relevant to the ecosystem. The software works with SHA-256 and Argon2 algorithms as referenced in the project material. It runs on Windows, macOS and Linux, and also appears in a browser and extension form. Check the project documentation for current coverage before relying on any specific network.