Using a usb as a "login key"?

[Schlibib]

Hello,

I'm trying to get a usb to work as a "username/password" thing. For example:
to login to a simple account one must plug in their usb(which i know have a serial number) to gain access.


Running example:
**
Please insert your USB to login.......

USB plugged in ..........

Access granted....


*

[kbw]

It all depends on the OS/Login Process.

This isn't quite what you're looking for, buut you may gain some insight into the problem. This describes how to encrypt a disk (Arch Linux) and store the key on a USB stick.
https://wiki.archlinux.org/index.php/Dm-crypt_with_LUKS#External_Storage_on_a_USB_Drive