apt-get install libpam0g-dev
apt-get install libssl-dev
apt-get install libncurses5-dev
apt-get install libreadline5-dev
insert USB device, re-writable
usbadm keygen /media/usbdrive cllee 4096
pam.d: 

auth    sufficient      pam_usb.so fs=ext2 check_device=-1 check_if_mounted=-1 force_device=/dev/sda1 log_file=/var/log/pam_usb.log allow_remote=1