README: Mention validity-sensors-initializer

README.md

@@ -9,7 +9,41 @@ To install Python dependencies run
 $ pip3 install -r requirements.txt
 ```
 
-## Getting the firmware
+## Initialization
+
+### Automatic factory reset, pairing and firmware flashing
+
+This repo includes `validity-sensors-initializer.py`, a simple tool that
+helps initializing Validity fingerprint readers under linux, loading their
+binary firmware and initializing them.
+
+This tool currently only supports these sensors:
+- 138a:0090 Validity Sensors, Inc. VFS7500 Touch Fingerprint Sensor
+- 138a:0097 Validity Sensors, Inc.
+Which are present in various ThinkPad and HP laptops.
+
+These devices communicate with the laptop via an encrypted protocol and they
+need to be paired with the host computer in order to work and compute the
+TLS keys.
+Such initialization is normally done by the Windows driver, however thanks to
+the amazing efforts of Viktor Dragomiretskyy (uunicorn), and previously of
+Nikita Mikhailov, we have reverse-engineerd the pairing process, and so it's
+possible to do it under Linux with only native tools as well.
+
+The procedure is quite simple:
+- Device is factory-reset and its flash repartitioned
+- A TLS key is negotiated, generated via host hw ID and serial
+- Windows driver is downloaded from Lenovo to extract the device firmware
+- The device firmware is uploaded to the device
+- The device is calibrated
+
+Once the chip is paired with the computer via this tool, it's possible to use
+it in libfprint using the driver at
+- https://github.com/3v1n0/libfprint/
+
+---
+
+### Getting the firmware
 
 It's possible to just extract [official Lenovo device driver for vfs0097](https://support.lenovo.com/us/en/downloads/DS121407) or [driver for vfs0090](https://support.lenovo.com/us/en/downloads/DS120491) (also [part of the SCCM package](https://support.lenovo.com/ec/th/downloads/DS112113) using [innoextract](https://constexpr.org/innoextract/) (available for all the distros), or `wine`.
 
@@ -18,7 +52,7 @@ The only reason you need to do this is to find `6_07f_lenovo_mis.xpfwext` (for v
       innoextract n1mgf03w.exe -e -I 6_07f_lenovo_mis.xpfwext # vfs0097
       innoextract n1cgn08w.exe -e -I 6_07f_Lenovo.xpfwext # vfs0090
 
-## Factory reset
+### Factory reset
 If your device was previously paired with another OS or computer, you need to do a factory reset.
 This will erase all fingers from the internal database and make the device ready for pairing.
 ```
@@ -26,7 +60,7 @@ $ python3 factory-reset.py
 $
 ```
 
-## Pairing
+### Pairing
 After performing a factory reset you need to pair your device with a host computer.
 This must be done only once, before you can enroll/identify/verify fingers.
 ```