# The Random Cipher

Go straight to the Random Cipher tool

## Introduction

The Random cipher is a type of substitution cipher, specifically a monoalphabetic substitution cipher. This means that you replace a letter in the plaintext with the same letter every time. For example, if you replace the letter "A" with "H", you must do that for every "A" in the entire plaintext.

The random cipher is a table that maps each letter of the plaintext to a unique letter in the ciphertext. But there's no rhyme or reason to what letters map to. Consider the following substitution table. There's no pattern to how the plaintext maps to the ciphertext. This is why it's called a Random substitution.

## Example

Consider the following random substitution table.

### Encryption

Based on the table "A" -> "S", "B" -> "B", "C" -> "X", "D" -> "E", "E" -> "M", etc. Let's use this to encrypt the message "ATTACK AT DAWN."

Encrypting
Plaintext A T T A C K   A T   D A W N
Ciphertext S A A S X Z   S A   E S Q L

### Decryption

To decrypt we go from the ciphertext back to the plaintext. Based on the table "S" -> "A", "B" -> "B", "X" -> "C", "E" -> "D", "M" -> "E", etc. Let's use this to decrypt the message "QSCA LKA FMA"

Decrypting
Ciphertext Q S C A   L K A   F M A
Plaintext W A I T   N O T   Y E T

## Random Substitution Tool

Below is a random substitution generator. When you press "Randomize" it will shuffle the letters of the alphabet to create a mapping from the plaintext to the ciphertext. You can use this to encrypt/decrypt messages below the generator.