KERBEROS turns the Cardputer into a real FIDO2 / U2F hardware security key. Press k, plug into a PC over USB, and register real passkeys.
- U2F and CTAP2, hand written on the ESP32-S3 (CBOR, COSE, ECDSA over NIST P256, attestation). No off the shelf FIDO library.
- Passkeys: non-resident and resident (discoverable). Usernameless sign in works.
- Verified end to end against Yubico's
python-fido2reference library, attestation and assertion signatures both check out. - On device approval. Credential keys are generated on device (mbedTLS) and never leave it.
- Boot key mode so FIDO is the sole USB HID device; exit reboots back to normal.
- Works today as a second factor on Google, GitHub, and any WebAuthn site.
Flash it
- Web flasher (Chrome / Edge): https://generaldussduss.github.io/poseidon/install.html
poseidon-factory.bin— full image, flash at offset0x0(bootloader + partitions + app).poseidon-launcher.bin— app only, drops into the bmorcelli Launcher slot at0x170000.
Full changelog in CHANGELOG.md.