# Classical Encryption Ciphers

##### Ludovic Rembert
Last Updated on January 1, 2024

Do you love “decoding” secret messages? Then Google’s Ingress is probably the perfect mobile game for you. It’s a type of capture the flag, social, decoding game that allows you to find secret messages hidden in media shared with players via their phones. These games require the players to know classic and advanced ways to decode these messages, also known as ciphers.

A cipher is a mechanical operation, also called an algorithm, that is used to decode small chunks of encrypted code. The Caesar Cipher is the most famous and easiest to use, as it maps each letter in the alphabet to another letter. This is also called a shift cipher.

This guide goes through each type of classical cipher currently known and how they work.

## What is Classical Encryption

Classical Encryption – This refers to one of the most common methods of encrypting plain text and it uses two simple techniques called Substitution and Transposition.

## What is the Caesar Cipher

Caesar Cipher – A Caesar Cipher is one of the oldest encryption methods that involve substituting each character in the plain text with a character which is a given number of positions before or after it.

## What is the Foursquare Cipher

Foursquare Cipher – The Foursquare Cipher uses four 5X5 grids of letters to encrypt the plaintext. It’s specialty is that it consists of two keywords, but is known as a relatively time-consuming method.

## What is One Time Pad

One Time Pad – This is a specialized encryption method where a one-time pre-shared keyword is used to encrypt plain text through modular addition.

## How to Use Playfair Cipher

Playfair Cipher – The Playfair cipher is a type of manual symmetric encryption where bigraphs, or pairs of letters are encrypted making frequency analysis more difficult.

## How to Use Transposition Ciphers

Transposition Ciphers – This type of cipher is performed by changing the order of the characters in the plain text. A common method is to write the plain text diagonally and read it out horizontally.

## How to Use Two-Square Cipher

Two Square Cipher – The two square cipher is a type of manual symmetric encryption that reduces the cumbersomeness of a four-square cipher but offers more security than a simple cipher.

## How to Use Vigenere Cipher

Vigenere Cipher – This is an encryption method that uses multiple interwoven Caesar ciphers to encrypt alphabetical plain text. It is renowned as a method that withheld attempts at cracking it for almost three centuries.

## How Does Cryptanalysis Work with Classical Ciphers

Most of the time, classical ciphers are too well-known to be utilized for any high security encryption in today’s world. However, they can still be used through automated processes by hackers to determine any holes and find whispers of vulnerabilities, as some systems are built upon older, classical encryption methods. This is why it’s important for businesses to update their cybersecurity systems and encryption methods all the time.

When you don’t have the specific key to decrypt an encrypted code, then you use cryptanalysis to discover the ciphers. This method uses a mathematical approach and known algorithms to decipher the ciphers.

In cybersecurity, cryptanalysis attacks can be used to decrypt hashed data and other encrypted information. The success of these attacks depends on the amount of time within your system, computer power available, and storage capacity.

Some of the most common cryptanalysis attacks include:

•  Brute force attack: A hacker uses known algorithms to try and guess any logical patterns of the plaintext, which can then be ciphered and compared to the original cipher.
•  Dictionary attack: A wordlist is incorporated to find matches of either plaintext or the key. It is mostly utilized for cracking passwords.
•  Rainbow table attack: In this latest type of attack, the ciphertext is used to compare with pre-computed hashes, resulting in matches that can be used to decrypt the text further.

## Wrapping Up

In cryptography, encrypted messages are ciphered and deciphered. By studying classical ciphers, you can use cryptanalysis to uncover certain bits of plaintext in a coded message. Classical ciphers are fun to study and utilize in simple puzzle cryptography, but most cybersecurity systems already protect against these known ciphers.