Intro

Many tasks that we perform in our everyday lives rely on encryption to keep our data or communication secret. Eg online banking, social media logins, using a wireless connection, using EFTPOS. When data is sent over the internet, others can intercept and read it. To protect ourselves we can encrypt it. Ordinary, readable plaintext text can be turned into unreadable encrypted data, known as ciphertext. 

Encrypted data needs to be easily decrypted, so the intended user of the data can make sense of it. This is usually done with the use of a secret value called a key - a piece of information that tells the user how to decrypt the data, turning the ciphertext back into plaintext.