tl;dr<p>Each fingerprint sensor was ultimately defeated by a different weakness. The Dell laptop's Goodix fingerprint sensor implemented SCDP [encrypted device communication] properly in Windows but used no such protections in Linux. Connecting the fingerprint sensor to a Raspberry Pi 4, the team was able to exploit the Linux support plus "poor code quality" to enroll a new fingerprint that would allow entry into a Windows account.<p>As for the Synaptic and ELAN fingerprint readers used by Lenovo and Microsoft (respectively), the main issue is that both sensors supported SCDP but that it wasn't actually enabled. Synaptic's touchpad used a custom TLS implementation for communication that the Blackwing team was able to exploit, while the Surface fingerprint reader used cleartext communication over USB for communication.