Utsuwa is a custom-engineered, open-source hardware security key based on the Pico Fido firmware. It combines modern FIDO2/WebAuthn security.
Unlike standard keys that use mechanical buttons, Utsuwa uses a Hall Effect Sensor, allowing for contactless authentication via a magnetic ring or charm.
Utsuwa (うつわ) comes from the Japanese word for "vessel", symbolizing a container for your digital soul.
IM SORRY I FORGOT TO PUSH THE CHANGES BEFORE SLEEPING LAST NIGHT xD
- Core: Powered by the Raspberry Pi RP2354A (Dual Core RISC-V/ARM, Secure Boot, Internal Flash).
- Auth: Contactless Magnetic Trigger (AH3377 Hall Effect Sensor). Zero moving parts.
- Visual: NeoPixel Glow (WS2812C-2020) for internal status illumination.
- Portable: Ultra-compact USB-A form factor with integrated PCB plug, and space for a keychain attachment.
- Robust: ESD protection on USB lines for enhanced durability.
This project's PCB was designed in EasyEDA Pro.
Total estimated cost: 39€
| Component | Part / Model | Qty | Notes |
|---|---|---|---|
| Microcontroller | Raspberry Pi RP2354A | 1 | Dual-core RISC-V/ARM with Secure Boot |
| Hall Effect Sensor | AH3377-W-7 | 1 | Contactless magnetic authentication trigger |
| RGB LED | WS2812C-2020 | 1 | Status indicator NeoPixel |
| Crystal Oscillator | ABM8-272-T3 (12 MHz) | 1 | External clock reference |
| Voltage Regulator | AP2112K-3.3TRG1 | 1 | 3.3V LDO power supply |
| USB Protection | USBLC6-2SC6 | 1 | ESD protection on USB lines |
| Inductor | 3.3µH (AOTA-B201610S3R3) | 1 | Buck converter filtering |
| Diode | 1N4148WS | 1 | Schottky diode for power path |
| Capacitors | 100nF, 4.7µF, 10µF, 18pF | 13 | Decoupling and filtering |
| Resistors | 27Ω, 33Ω, 1kΩ | 4 | USB termination and pull-ups |
| PCB Fabrication | Custom USB-A form factor | 1 | Compact design with integrated plug |
Complete CSV with supplier links: bom.csv
For this project I'm not going to be making a CAD case of model, because I made the PCB itself beautiful, and seeing the electronics in this will be very cool. I have two ideas for protecting the electronics though: either use epoxy to cover everything, or I will use a clear shrinking tube to cover the PCB. I think the latter will give it a better look.
This board runs on the Pico Fido open-source firmware. To support the custom hardware (RP2354A + Hall Effect + WS2812), you must compile the firmware with the following settings in board_config.h:
// Flash Size for RP2354A (Internal 2MB)
#define PICO_FLASH_SIZE_BYTES (2 * 1024 * 1024)
// Authentication Button (Hall Effect Sensor)
// Hall Effect pulls Low when magnet is present
#define BUTTON_PIN 18
#define BUTTON_PULL UP
// Status LED (WS2812C-2020)
#define HAVE_WS2812
#define WS2812_PIN 19
#define WS2812_POWER_PIN -1 // Directly powered by VBUSFirst Time: Short the BOOT pad with the lanyard loop copper on the front of the PCB with tweezers or some other conductive material while plugging it in.
Mount: The device will appear as a USB Mass Storage Drive (RPI-RP2).
Flash: Drag and drop your compiled .uf2 file.
Reboot: The device will reboot as a FIDO2 Security Key.
Designed with 💙 by 𝕲𝕭
Special thanks to the Hack Club community for their support