# solokeys/solo1

Solo 1 firmware in C

Repository: https://github.com/solokeys/solo1
Canonical: https://ross.abutalabs.com/products/solo1
Homepage: https://solokeys.com/
Language: C
License: NOASSERTION
License Family: other
Topics: fido2, u2f, hardware, security, webauthn
Last push: 2022-11-13T10:16:36+00:00

## Health v2 (maintenance only)
Score: 23/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 8, longevity 100
- inputs: {"age_days": 2911, "days_push": 1389, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2384, forks 290 (observed 2026-08-28T04:06:42.559883+00:00)

## What it is
Solo 1 is the open-source C firmware for the Solo security key, implementing FIDO2 (CTAP2) and U2F (CTAP) over USB and NFC on an STM32L432 microcontroller. It can also run as a standalone desktop application for development without hardware, and an unlocked 'Solo for Hacker' variant allows custom firmware.

## Use cases
- build custom firmware for a FIDO2 security key
- implement two-factor authentication with a hardware token
- passwordless login with WebAuthn
- test FIDO2/U2F authentication without hardware
- audit open-source security key firmware

## When to choose
- you want an open-source, auditable FIDO2/U2F security key
- you want to customize or experiment with security key firmware on a NUCLEO-L432KC or Solo Hacker
- you need a desktop simulation of a FIDO2 authenticator for development

## When to avoid
- you want the latest Solo 2 / Trussed-based firmware (use solokeys/solo2 instead)
- you need OpenPGP or SSH key support out of the box
- you need a maintained production firmware - this repo's latest release is from 2022

## Facets
- artifact type: application
- maturity: maintenance
- function: auth, security, cryptography, embedded
- domain: security, hardware, privacy
- platform: embedded, windows, cross-platform
- tags: fido2, u2f, webauthn, security-key, firmware, usb, nfc, passkeys, two-factor-authentication, hardware-token, authentication, linux, macos

## Member repositories
- solokeys/solo1 (main) score 23

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:06:42.559883+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T02:34:40.542470+00:00, confidence not recorded.
  - readme: https://github.com/solokeys/solo1 (fetched 2026-08-28T04:06:42.559883+00:00, sha de1f86478838)
  - homepage: https://solokeys.com/ (fetched 2026-08-29T10:15:32.049911+00:00, sha de0baa4a8989)
- Data as of 2026-08-30T08:39:29.467469+00:00.