pam_usb is a PAM module that provides hardware authentication for Linux using ordinary USB flash drives, SD cards, MMC, etc.
Using this, you’ll be able to login without a password by simply connecting a USB stick or memory card to your computer. This USB authentication also works when running terminal commands that require superuser, you will not be prompted for a password when using sudo for example.
A quick note of caution: With this tutorial, you’re creating a powerful key to open your Linux install wide. It saves you entering your superuser password, but it does the same for anyone with the USB key. Guard it carefully.