Pass Vault
A biometric hardware security key that acts as a USB HID keyboard, mapping 10 fingerprints to specific passwords or macros.
Author: Polojan Radu-Mihai
GitHub Project Link: https://github.com/UPB-PMRust-Students/fils-project-2026-radupolojan
Description
The Pass Vault is a hardware security device that stores encrypted passwords and types them automatically when a recognized fingerprint is scanned. By acting as a USB keyboard (HID), it requires no special software on the host PC. It features a Multi-Profile interface where each finger triggers a different credential, all managed via a secure USB-C smartphone or pc companion app.
Motivation
I chose this project to create a physical-first security solution that eliminates the vulnerability of software-based password managers. It combines biometric authentication with Rust’s memory safety to ensure that credentials remain unhackable and accessible only by the physical owner.
Architecture
Log
Week 5 - 11 May
- Bought and collected all the hardware components (Olimex RP2350 board, SFM-V1.7 sensor, and XIAO RP2040 board).
- Checked the pinouts and connection diagrams for the parts.
Week 12 - 18 May
- Wrote most of the microcontroller firmware code in Rust.
- Studied and tested the
embassyandusblibraries to understand how asynchronous hardware communication works. - Made the fingerprint sequential enrollment logic and the USB keyboard emulation.
Week 19 - 25 May
- Created the desktop companion application for the PC using egui.
- Designed the 3D case for the device and successfully 3D-printed the final physical enclosure.
Hardware
The project uses the high-pin-count RP2350B, featuring 16MB FLASH and a 8MB PSRAM for advanced data handling and an XIAO RP2040 as the debugger.
Schematics
Bill of Materials
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| Device | Usage | Price |
|---|---|---|
| RP2350-PICO2-XXL OLIMEX | Main MCU | 55 RON |
| Senzor amprenta SFM-V1.7 | Biometric authentication | 94 RON |
| Seeed Studio XIAO RP2040 | Hardware SWD Debug Probe | 30 RON |
Software
| Library | Description | Usage |
|---|---|---|
| embassy-rp | Async runtime and HAL for RP2040/RP2350 | Provides async drivers for hardware timers, UART communication with the sensor, and internal flash controllers. |
| embassy-usb | Asynchronous USB device stack | Handles the concurrent USB stack, configuring the device as a composite USB CDC Serial class and USB HID Keyboard. |
| usbd-hid | USB HID class and report descriptor generator | Generates the official boot keyboard reports used to type decrypted characters into any OS host text-field. |
| embedded-storage | Storage traits for embedded systems | Provides standardized interfaces to safely interact with non-volatile memory sectors. |
| eframe / egui | Immediate mode GUI framework for Desktop | Drives the minimalist PC companion application interface, managing background thread message passing channels. |
| serialport-rs | Cross-platform serial port library for Rust | Enables the desktop client app to perform background plug-and-play USB hardware polling based on unique VID/PID signatures. |