LFSR - Linear Feedback Shift Register

A linear feedback shift register is a collection of bits that shifts when triggered, and the next state is a linear function of its previous state. We use right-shift (>>) as the shift operation and XOR (^) as the linear function to generate the next state of the register.

This repository contains a demonstration of LFSR in

• generating random bits
• generating random numbers
• scrambling and unscrambling a stream of bytes

You can read more about LFSRs on Pseudorandom Number Generation using LFSR.

Sample Usage

Generating Random Bits

The following command generates 10 random bits using a 4-bit LFSR with Seed 0b1001, tap at bit position 1.

$ go run main.go random-bits -s 9 -t 1 -n 4 --count 10
1
0
0
1
1
0
1
0
1
1

Generating Random 8-bit Numbers

The following command generates 10 random 8-bit numbers using a 4-bit LFSR with Seed 0b1001, tap at bit position 1.

$ go run main.go random-numbers -s 9 -t 1 -n 4 -k 8 --count 10
154
241
53
226
107
196
215
137
175
19

Scrambling a text file

To see scrambling in action let's first create a text file with some secret content

$ echo "british troops entered cuxhaven at 1400 on 6 may - from now on all radio traffic will cease - wishing you all the best. lt kunkel." > secret.txt

Now fire the following command that scrambles the file with the default configurations

$ go run main.go scramble -f secret.txt

The command creates a scrambled file with the name enc.secret.txt and if we cat the scrambled file, we get the following jargon

$ cat enc.secret.txt
D���#РɃ��az�$B���?��9��R���,7�#Vhq�%��\�I>����ӻ��jq_�c`��yp��VM�u/�|���e!�%

Unscrambling a scrambled file

To unscramble the scrambled file and reveal the secret content fire the following command

$ go run main.go unscramble -f enc.secret.txt

The command unscrambles the scrambled file and generates another file with the name dec.enc.secret.txt and if we cat it, we get the original content

$ cat dec.enc.secret.txt
british troops entered cuxhaven at 1400 on 6 may - from now on all radio traffic will cease - wishing you all the best. lt kunkel.