Turning an RP2350 into a Security Key

I recently came across a project called PicoKeys, and I thought it was a pretty cool use of these tiny development boards.

PicoKeys is an open-source firmware project that can turn boards based on the RP2040, RP2350/RP2354, and ESP32-S3 into different types of security devices. Depending on the firmware, you can use them for FIDO2 passkeys, OpenPGP, or other cryptographic applications.

The RP2040 is supported, but I decided to go with an RP2350 because it has a stronger hardware-security foundation. The RP2040 lacks some of the built-in security features available on the newer RP2350.

A Tiny Security Key

For the hardware, I picked up this tiny RP2350 development board with a USB-A connector built directly into the PCB.

That makes it particularly convenient for this project. There isn’t much to it — flash the firmware, plug it into a USB port, and you have a functional security key.

I then 3D printed a small enclosure for it.

3D model: RP2350 USB Dongle Case on Printables

Once everything was assembled, I ended up with a tiny security key that I can actually use for logging into services that support FIDO2/passkeys.

It’s one of those projects I really like because there isn’t much hardware involved, but you’re taking a cheap development board and turning it into something genuinely useful.

And of course, there’s something satisfying about having a 3D-printed security key that I made myself sitting on my keychain.

What I used

• MCU: RP2350
• Firmware: PicoKeys
• Connection: USB-A
• Enclosure: 3D printed
• Use: FIDO2 / passkey authentication