I have a non-usb finger print reader based on UART and I am trying to interface it to my computer.

Basically when the system is booted and is running I can send serial data to my finger print reader and get a reply typically an authentication of a finger print back. I have the device specification and I am communicating with the device by using termios and my problem is I want to do this in the login-screen.

So, my Idea is to run a custom program while the system is at login screen to communicate with my device and get the authentication back. The device stores the fingerprint templates on board and just sends an authentication packet back.

Any suggestions to make this happen at login screen would benefit me.

Thank you.

You will need to investigate the use of PAM for the authentication.

The authentication library you use can be made optional (if it sees the device, then it could continue).

But the problem is - it can also be spoofed. The fact that it is external makes it vulnerable to wiretapping and replay attacks.

Now if the serial interface is encrypted then it would be better... but it also makes both sides more complex (both reader and PC), expensive and harder to use.

But I haven't read of any fingerprint readers that haven't been bypassed with relatively silly attacks.