$ sudo apt-get update
$ sudo apt-get install libffi6-udeb 

libffi6-udeb is installed in your system.

Make ensure the libffi6-udeb package were installed using the commands given below,

$ sudo dpkg-query -l | grep libffi6-udeb *

You will get with libffi6-udeb package name, version, architecture and description in a table

libffi6-udeb package basic information: