This design is a complete AES-256 encryption/decryption system that works in Cipher Block Chaining (CBC) mode, it includes 3 main blocks:

Each Xilinx FPGA has a unique 64bit identification number preprogrammed into it - this is known as the DNA. This ID can be very useful for many different purposes..

There are a couple of posts in the notes section of this site about using the USR_ACCESS primitive for identifying bitstreams..

This is a simple filter for single-bit serial inputs, digital I/O or can also be used as part of a debounce circuit for pushbuttons and dipswitches...