Turn a spare laptop into an airgapped Bitcoin signer.
Thunder Den's development image boots from USB and runs in memory. Import your existing recovery words, review transactions on the laptop and exchange data through QR codes.
Thunder Den is designed to be easy to audit with AI before you use it. We aim for small, clear code, few dependencies and a simple build process.
Inspired by SeedSigner's stateless approach and descriptor-based hardware-wallet designs, including Ledger and BitBox02. Bitcoin Core provides the Bitcoin functionality at its heart.
Status: v2 is under development. Docker can build a development image; physical-hardware validation and release verification are ongoing. Use test networks only; this project is not ready to protect mainnet funds.
- Your seed and private keys stay in RAM.
- Thunder Den saves no wallet state between boots.
- Thunder Den does not write to the boot USB or the laptop's disks.
- The running signer cannot access disk storage, Ethernet, Wi-Fi or Bluetooth.
- Wallet data and transactions move through QR codes.
- You review and approve transactions on the laptop before signing.
- Untrusted input stays within validated data interfaces; code changes, secret export and approval bypass are forbidden.
- You can rebuild the released USB image and compare its SHA-256.
- Import English BIP39 recovery words and an optional ASCII passphrase once per session.
- End a session to clear loaded keys, then power off or start a new session.
- Descriptor-based wallets, including SegWit and Taproot Miniscript.
- BIP-388 wallet policies with seed-bound registration proofs.
- BIP44, BIP49, BIP84 and BIP86 defaults without prior registration.
- Partial signing when other signatures or spending conditions are still needed.
- UR v2 scanning and animated QR output, with the scanner isolated from keys and approval.
- One USB image for x86-64 laptops with legacy BIOS or UEFI.
- A Docker/Compose build using pinned Linux containers with native build tools.
Thunder Den relies on your hardware and firmware, your build computer and pinned dependencies such as Bitcoin Core and Linux. Reviewing this repository still leaves those dependencies to review or trust.
Start with the source-reading map, the dependency inventory and the build and test instructions.
Firmware behavior and physical attacks on memory are outside the software's guarantees. RAM-only operation means no persistent wallet storage, not a promise that every trace in physical memory becomes unrecoverable at power-off.
Tests and development tools run on the build computer. They are not part of the production image. Software-wallet integrations and reference clients will follow the signer protocol; no particular software wallet defines Thunder Den's design.
Contributions are welcome: bug fixes, review findings, documentation and build or hardware test reports are especially useful. Simplicity and auditability take priority over feature count. Changes must justify their complexity, dependencies and attack surface; security additions and refactors need a concrete rationale. See the short contribution guide before opening a pull request.
Thanks to SeedSigner for inspiration, Salvatore Ingala (Ledger) for the wallet-policy and registration design and Bitcoin Core's contributors for the Bitcoin engine. Thunder Den also builds on Linux, Buildroot and the other upstream projects listed in its dependency documentation.