Introduction

Encryption is used to keep data secret. In its simplest form, a file or data transmission is garbled so that only authorised people with a secret key can unlock the original text. If you're using digital devices then you'll be using systems based on encryption all the time: when you use online banking, when you access data through wifi, when you pay for something with a credit card (either by swiping, inserting or tapping), in fact, nearly every activity will involve layers of encryption. Without encryption, your information would be wide open to the world – anyone could pull up outside a house and read all the data going over your wifi, and stolen laptops, hard disks and SIM cards would yield all sorts of information about you – so encryption is critical to make computer systems usable.