The Decoder Ring

I worked on this project while attending Thinkful/Chegg Skills's Software Engineering bootcamp. This project includes working with code through JavaScript, and writing tests through Mocha and Chai.

Decoder Ring Website

The Caesar Shift

The first decoder is a Caesar Shift, a type of substitution cipher originally used by Julius Caesar. It relies on taking the alphabet and "shifting" letters to the right or left, based on the typical alphabetic order. For example, if you were to "shift" by +3, the letters would shift to the right and "A" would become "D". You can choose to shift anywhere from -25 to +25.

Shift : 3
"thinkful" -> "wklqnixo"

Shift : -3
"crlqnv" --> "zoinks"

The Polybius Square

The Polybius Square is a cipher that is achieved by arranging a typical alphabet into a grid. Each letter is represented through a coordinate.

      1      2      3      4      5 
1     A      B      C      D      E
2     F      G      H     I/J     K
3     L      M      N      O      P
4     Q      R      S      T      U
5     V      W      X      Y      Z    

For example, the letter "B" would be represented by the numerical pair "21".

I and J are both paired together as 42 in the Polybius Square, so if you were to put the word "jill", the result would be "42421313".

But if you were to put "42421313", you would get "(i/j)(i/j)ll".

"Buddy" --> "2154414145"

"3251131343 2543241341" --> "hello world"

"4432423352125413" --> "th(i/j)nkful"

The Substitution Shift

The Substitution Cipher requires a standard alphabet and a substitution alphabet. Letters from the standard alphabet will be transposed to the standard alphabet. This cipher requires a substitution alphabet of exactly 26 characters. The substitution can have special characters such as "!, #, $, etc."

For Example:

Real Alphabet: *A B C D E F G H I J K L M N O P Q R S T U V W X Y Z*
Substitution:  *Q W E R T Y U I O P A S D F G H J K L Z X C V B N M*

"Blue" --> "wsxt"

"pxdhofu" --> "jumping"