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name: bitcoin-hardware-seedsigner description: | SeedSigner: DIY Bitcoin signing device. Raspberry Pi Zero + camera

• screen. Boots from microSD, no permanent state. Stateless airgap signing. USE WHEN: building / supporting SeedSigner, designing stateless signing flows. allowed-tools: Read, Grep, Glob

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SeedSigner

DIY Bitcoin hardware wallet:

• Raspberry Pi Zero (or compatible) + camera + small screen.
• Boots from microSD running SeedSigner image.
• Stateless: no seed stored on device. User enters seed each session via dice / QR / hand-typed words.

Hardware (DIY)

• Raspberry Pi Zero W (~$10).
• Camera Module 1.3 / 2.1 (~$25).
• Waveshare 1.3" screen (~$20).
• 4 GPIO buttons.
• microSD with SeedSigner image.

Total: ~$60 in parts, plus 3D-printed case.

Operation

1. Boot SeedSigner from microSD.
2. Enter seed via:
   • Dice rolls (entropy → seed).
   • Manual word entry.
   • SeedQR scan (encoded BIP39 mnemonic).
3. Use as airgap signer for PSBT (QR transport).
4. Power off → seed wiped from RAM.

No persistent storage of seed = no risk of physical seizure revealing keys.

Compatible wallets

• Sparrow Desktop.
• Specter Desktop.
• Nunchuk.

QR transport: animated QR for PSBT in/out.

Use cases

• DIY enthusiasts wanting open hardware.
• High-security applications: no firmware backdoors possible (you build it).
• Educational: understand how HW wallets work.

Compared to commercial

Aspect	SeedSigner	Commercial HW
Cost	$60 DIY	$50-500
Auditability	Full (you built it)	Trust manufacturer
Convenience	Lower (boot every session)	Higher
Permanent storage	None (stateless)	Encrypted internally
Maintenance	DIY	Vendor support

Limitations

• Slower signing (boot time + manual seed entry).
• No tamper-evident hardware — Raspberry Pi has no SE.
• Camera quality affects QR scan reliability.

See also

• krux/SKILL.md
• specter-diy/SKILL.md
• passport/SKILL.md
• coldcard/SKILL.md
• ../wallets/backup/SKILL.md