What is encryption? The backbone of computer security, explained

If you’ve read anything about technology in the last few years, you may have seen the term “encryption” floating around. It’s a simple concept, but the realities of its use are enormously complicated. If you need a quick 101 on what encryption is and how it’s used on modern devices, you’ve come to the right place. But first, we have to start at the beginning.

Further reading: 5 easy tasks that supercharge your security

The basics of cryptography

At the most simple, basic level, encryption is a way to mask information so that it can’t be immediately accessed. Encryption has been used for thousands of years, long before the rise of the information age, to protect sensitive or valuable knowledge. The use and study of encryption, codes, and other means of protecting or hiding information is called cryptography.

The most simple version of encryption is a basic replacement cipher. If you use numbers to indicate letters in the Latin alphabet, A=1, B=2, et cetera, you can send a message as that code. It isn’t immediately recognizable, but anyone who knows the code can quickly decipher the message. So, a seemingly random string of numbers:

20 8 5 16 1 19 19 23 15 18 4 9 19 19 23 15 18 4 6 9 19 8

…can become vital information, to someone who knows how to read it.

t he p a s s w o r d i s s w o r d f i s h

That’s an incredibly basic example, the kind of thing you might find in the classic “decoder ring” toy. Archaeologists have found examples of people encrypting written information that are thousands of years old: Mesopotamian potters sent each other coded messages in clay, telling their friends how to make a new glaze without letting their competitors know. A set of Greek substitutions called the Polybus square is another example, requiring a key to unlock the message. It was still being used in the Middle Ages.

Cryptography in wartime

Cryptography is used to protect information, and there’s no more vital application than warfare. Militaries have encrypted their messages to make sure that enemies won’t know their plans if communication is intercepted. Likewise, militaries also try to break encryption, discover the…