Android LUKS app
Android LUKS is Security application that is open source under the GPL-3.0-only license.android-luks is an app that allows secure LUKS unlocking using usb accessory mode without typing your LUKS password.
The app has two functions: Init and Unlock. Init creates a new random encryption key and securely encrypts it using biometrcs. Unlock gets biometrics, decrypts the key and sends it over USB.
How to use
Install the Android app, install the Linux host program and scripts, initialize the key and plug your phone over USB. Now, when your Linux machine boots, you should see the Android app automatically popping up. As soon as you press "Unlock" button and confirm your biometrics, the boot process will continue without typing in the password.
