Krux
Bitcoin-only airgap signer for Sipeed M5StickV and Maix Amigo hardware. Open-source firmware. Stateless: seed enters on use.
Hardware
- Sipeed M5StickV (~$50).
- Maix Amigo (~$80, larger screen).
- Built-in camera + display.
- USB-C charging only (no data).
Operation
- Power on, boot Krux firmware from internal flash.
- Enter seed via:
- 24-word manual entry.
- SeedQR scan.
- Tinyseed (metal plate decoder).
- Sign PSBTs via animated QR.
Features
- Multi-language UI (English, Spanish, French, etc.).
- Multi-output signing (PSBT, message signing).
- BIP39 word entry helper.
- Tiny seed decoder for steel backup plates.
Compatible wallets
- Sparrow.
- Specter.
- BlueWallet (limited).
Use cases
- Cheaper than SeedSigner DIY if you don't have a Pi.
- Educational — explore HW signer internals.
- Privacy-focused — no permanent identity.
Limitations
- Smaller screen (M5StickV).
- Sipeed hardware availability varies by region.
- No SE — same caveat as SeedSigner.