Encryption

What is Encryption?

Within Computer Science, which covers algorithms, programming, data, networks, hardware and safe, responsible use of technology, this topic explains Encryption. Computing topics explain how software, hardware and data work, with diagrams and models that show each step in order.

Check that you can explain Encryption in your own words and give one example from everyday life. If you can do that, you have understood the core idea.

Understanding Encryption helps you design, test and explain programs, websites and systems, from small projects to exam questions.

Encryption in detail

Encryption scrambles data (plaintext) into unreadable form (ciphertext) using an algorithm and a key, so that only people with the correct key can decrypt it. Early examples include the Caesar cipher, which shifts letters by a fixed number.

Symmetric encryption uses the same key to encrypt and decrypt, and is fast, but the key must be shared securely. Asymmetric (public-key) encryption uses a pair of keys, a public key to encrypt and a private key to decrypt, which solves the sharing problem and underlies HTTPS, secure email and digital signatures. Encryption protects online banking, messages and stored data.

How the interactive helps you understand Encryption

Click a step, or use the Previous and Next buttons, to move through the sequence one stage at a time. Auto-play moves on for you.

Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Encryption.

Real-life uses and examples

• Recognise Encryption in an app or device you use every day.
• Apply Encryption when you design a small program, website or spreadsheet.
• Explain Encryption to someone new to computing by comparing it to a familiar process.

Common mistakes to avoid

• Using the term without being able to say what the computer actually does.
• Testing only the normal case and forgetting the edge cases.
• Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.