S ShieldSigner / build notes

OPEN HARDWARE / BITCOIN / SMARTCARDS

Build it.
Understand it.

A pocket Bitcoin signer, built around Luckfox and contact smartcards. The board, the software, and the reasoning behind every part—written down as we build.

Explore the hardware ↗Read the build guides →

A development project based on 3rdIteration’s ShieldSigner fork.

CARRIER / REVISION NOTES01 — LUCKFOX
Top copper view of the ShieldSigner Luckfox carrier PCB
53 PCB COMPONENTSCONTACT SMARTCARD + 2.8″ LCD
KiCad checks pass0 active findings · 2 documented DNP exceptions
Linux image buildsCached build: 27m 5s · 5.5× faster
Next: hardware bring-upLCD qualification & UR2 config pending

THE PROJECT, EXPLAINED

From copper to card commands.

Start with a subsystem. Each guide connects the design choices to the way the device actually works.

Hardware / 01

Hardware architecture

Power, processor, screen, buttons and the card reader.

↗Smartcards / 02

Cards & the Linux reader

Socket wiring, SeedKeeper versus Satochip, and PC/SC over UART.

↗Build / 03

Parts & JLCPCB assembly

Carrier population, supplier matches and unresolved LCD qualification.

↗Software / 04

Buildroot & firmware

Pinned inputs, successful builds, caches and possible Linux-free work.

↗

TWO CARDS. TWO DIFFERENT JOBS.

Store a seed.
Or sign on the card.

SeedKeeper keeps secrets for the host to load. Satochip derives keys and signs on the card. Our contact reader supports the interface; the applet determines what you can do.

Understand card compatibility →
SEEDKEEPER
▦
PIN-protected storageSeed enters host memory when loaded
SATOCHIP
▦
On-card signingHost reviews and requests the signature

EVIDENCE BEFORE ASSUMPTIONS

A working design is a beginning.

Electrical checks and reproducible builds are recorded. Physical assembly, LCD fit, card operation and the power budget still need bench verification. This site keeps those distinctions visible.

Follow the bring-up guide ↗Get the board files →