An introduction to simple cryptography

In 2021, Facebook reported that over 100 billion messages were sent on its platforms every day, including Facebook Messenger, WhatsApp, and Instagram Direct. All of these messages are private between individuals or groups of individuals.

As well as this large volume of social media messages, it is estimated that over 250 million online sales took place in January 2021 alone with a value of approximately £9.4 billion – a huge amount of money!

It’s really important that all of these messages and online sales are kept private so that people who shouldn’t be able to see them can’t, and no one can change them if they aren’t meant to. This is where cryptography comes in; cryptography ensures the privacy, security and integrity of data.

What is cryptography?

Cryptography has been used for thousands of years to keep information secure, dating back to the ancient Greeks and their use of the scytale (more on this later!).

Today, cryptography is a critical component in protecting privacy, ensuring security, and maintaining data integrity in modern communication systems. By using encryption, digital signatures, and hash functions, cryptography provides a reliable way to protect sensitive information and maintain trust in digital communication.

Cryptography is used in various applications, including secure communication over the internet, electronic commerce and access control systems. One of the most common uses of cryptography is to protect data in transit (when it is being sent over a computer network, such as the internet), such as emails and online banking transactions.

To ensure secure communication, cryptography uses a variety of algorithms and techniques, including symmetric key cryptography, public key cryptography, and hash functions. There’s a lot of maths in cryptography! We will introduce each of these concepts later in the course.

In this activity we will look at common ‘use cases’ (examples) of different cryptographic techniques and how they achieve their purpose.