In the Second World War the German military used a machine called Enigma to send secret messages across battlefields and oceans.

Enigma scrambled every letter of a message into a completely different letter using a system of rotating mechanical wheels. The recipient had an identical machine set to the same configuration and could unscramble the message instantly. Anyone intercepting the transmission without an Enigma machine and the correct daily settings saw nothing but random gibberish.

The Allies knew the Germans were communicating. They could intercept the transmissions. But for years they could not read them — because without the key to the code the messages were completely meaningless.

Breaking Enigma required one of the greatest intellectual efforts in human history — led by a mathematician named Alan Turing whose work at Bletchley Park is widely credited with shortening the war by years and saving millions of lives.

That story — a message scrambled beyond recognition, readable only by those with the right key — is the story of encryption. And a version of it is happening billions of times every single day on every device connected to the internet.

The Problem Encryption Solves

Every time you send a message, make a payment or log into a website your data travels across networks that are not private. It passes through routers, servers and infrastructure owned by companies and governments around the world. In theory anyone with the right access and tools could intercept that data as it travels.

Without encryption intercepted data would be perfectly readable. Your passwords, your bank details, your private messages, your medical records — all of it would be visible to anyone positioned to intercept it. The internet as we use it today would be completely unsafe.

Encryption solves this by scrambling your data into unreadable gibberish before it travels — and only unscrambling it when it arrives at the intended destination. Anyone intercepting it in transit sees nothing useful.

The Combination Lock Language

Imagine you and a friend want to pass secret notes in class without anyone else being able to read them.

You agree on a simple code before you start — every letter shifts three places forward in the alphabet. A becomes D. B becomes E. C becomes F. And so on. You write your message using the code. Your friend receives it and shifts every letter three places back to read it. Anyone else who intercepts the note sees complete nonsense.

That shared rule — shift three places — is your key. Anyone who knows the key can read the message. Anyone who does not sees gibberish.

This is the fundamental idea behind encryption. A piece of data gets transformed using a mathematical rule — the encryption algorithm — and a specific value — the key. The result is unreadable to anyone without both the algorithm and the correct key.

Modern encryption uses mathematical operations so complex that even the most powerful computers on earth would take longer than the age of the universe to crack them by trying every possible key combination. The basic concept is the same as your classroom code. The mathematics behind it is incomparably more sophisticated.

Two Types of Encryption Worth Knowing

There are two main types of encryption that power almost everything you do online.

Symmetric encryption uses the same key to both scramble and unscramble data. It is fast and efficient — perfect for encrypting large amounts of data quickly. The challenge is that both parties need to share the same key securely before they can communicate. If someone intercepts the key during that exchange the encryption is compromised. This is the Enigma problem — the Germans had to distribute their daily settings to every operator which created opportunities for the Allies to obtain them.

Asymmetric encryption solves this problem elegantly. It uses two mathematically linked keys — a public key and a private key. If you have been following this series you will recognise these immediately from our article on public and private keys in crypto. Your public key scrambles the data. Only your private key can unscramble it. You share your public key with the world freely. Your private key never leaves your possession.

This means anyone can send you an encrypted message using your public key. But only you can read it because only you have the private key to unscramble it. No prior secure exchange of keys is needed. The asymmetry solves the distribution problem that made symmetric encryption vulnerable.

In practice most modern systems use both. Asymmetric encryption establishes a secure connection and exchanges a temporary symmetric key. Symmetric encryption then handles the actual data transfer because it is significantly faster. This is exactly what happens when you connect to a website with HTTPS — the padlock in your browser confirms this process has completed successfully.

How This Protects You Every Day

Every time you see HTTPS at the start of a web address your connection to that site is encrypted. Nobody between you and that server — not your internet provider, not a hacker on the same network, not anyone monitoring the infrastructure in between — can read what you are sending and receiving.

Every time you send a message on WhatsApp end to end encryption ensures that only you and the recipient can read it. Not WhatsApp. Not any government that demands access. Not any hacker who intercepts the transmission. The message is scrambled on your device and only unscrambled on the recipient's device.

Every time you make an online payment your card details are encrypted before they leave your browser. The payment processor receives encrypted data that is meaningless to anyone who intercepts it in transit.

Every time you unlock your phone with a PIN or fingerprint the data stored on your device is encrypted in a way that makes it unreadable without your specific authentication. Lose your phone and a thief cannot simply plug it into a computer and read your files.

Encryption is the invisible infrastructure that makes the modern digital world safe enough to use.

The Threat on the Horizon

Everything described in this article — the asymmetric encryption protecting your messages, your payments and your crypto wallets — rests on a mathematical assumption. That certain problems are too hard for any computer to solve in a reasonable amount of time.

Quantum computers threaten to shatter that assumption.

On March 25 2026 Google published what many in the security community are calling the most urgent warning about encryption in the history of the internet. They set a hard deadline of 2029 for completing their own transition to post quantum cryptography — two years ahead of the NSA's target and six years ahead of broader government benchmarks. Cloudflare immediately followed with the same deadline.

The reason for the urgency is a threat called Harvest Now Decrypt Later. Bad actors — including state level intelligence agencies — are already intercepting and storing encrypted data today. They cannot read it yet. But they are stockpiling it for the day when a quantum computer powerful enough to crack current encryption exists. When that day arrives — which Google now believes could happen before 2029 — all that stored data becomes readable instantly. Conversations you had years ago. Transactions you made. Messages you sent. All of it potentially exposed.

The Ethereum Foundation responded immediately by launching a Post Quantum Ethereum initiative to secure the network's billions of dollars in value before 2029. Bitcoin faces the same challenge — the elliptic curve encryption protecting every Bitcoin wallet is specifically vulnerable to sufficiently powerful quantum attacks.

The encryption protecting the digital world is not broken. But the clock is running.

The Bigger Picture

Alan Turing broke Enigma not by finding a flaw in the encryption itself but by exploiting patterns in how the operators used it — human error rather than mathematical weakness. The encryption was sound. The people implementing it were not always careful.

That lesson applies directly to digital security today. Modern encryption algorithms are mathematically robust. The vulnerabilities that lead to real world breaches are almost always in how encryption is implemented, managed and used by people — weak passwords, reused credentials, phishing attacks that trick people into handing over their keys willingly.

Understanding encryption does not just make you more informed about technology. It makes you a more careful and more secure user of the digital world you inhabit every single day.

And it all started with a mathematician, a mechanical machine and the desperate need to read messages that were never meant to be read.

Here is something worth thinking about — if quantum computers could crack today's encryption within the next few years and bad actors are already harvesting your encrypted data right now waiting for that moment — how does that change the way you think about what you share online today? Drop your thoughts in the comments — I read and reply to every one.