A substitution cipher is a cipher that maps each symbol in the plaintext to a symbol according to a permutation of the alphabet. A breakpoint is a location in the ciphertext where the cipher changes.

This project provides a simple implementation of the Caesar Cipher, a substitution cipher where each letter in the plaintext is shifted by a specific number of positions down or up the alphabet. The ...

Learn how to implement a classic substitution cipher in C! This step-by-step tutorial walks you through encoding and decoding messages by replacing each letter with another according to a fixed key. A ...

Hill cipher cryptosystem is a linear algebra‐based classical polygraphic substitution cipher‐based technique. If the encryption key matrix (also called the key matrix) is not invertible, obtaining the ...

Hannah handed me a piece of paper with the following string of letters. “Each letter stands for another one,” said Hannah. “Ooh, a substitution cipher!” I thought. But I was stumped. “Is this just one ...

In 1854, Sir Charles Wheatstone invented the cipher known as "Playfair," named for his friend Lyon Playfair, first Baron Playfair of St. Andrews, who popularized and promoted the cipher. Its ...