LFSR Factoids
Encryption done easy
Introduction
Check out the March 2021 Blog post for a general description of this project. That will lead into the project described here. The first video details the project with a power-point presentation but briefly, this project consists of a breadboarded 24-bit linear feedback shift register where the starting point is determined by 3-bytes of seed data provided by a serial-in, parallel-out shift register so the LFSR pattern can be altered by the controlling microcontroller.
Project Description
The breadboard circuit is controlled via an Arduino and has an external +5V supply to run all the chips and LEDs on the breadboard plus a second circuit board.
The second board is attached that has the same LFSR circuit on it with a decrypt XOR gate. So the bit stream with the message comes to this board and is blended with the bit stream derived locally and passes through this XOR. The output is sent back to the breadboard to be displayed by a yellow LED. When the message comes through, this LED lights up with the message pattern. The Arduino creates the clocking, so when the message is sent, the clocking is slowed down so you can see it. Then once the message is seen, the clock speeds up and the bit stream continues out to count 132 and stops. Normally, the stream would be continuous and the message just comes through and no one is the wiser that it occurred.