If used correctly, end-to-end encryption can help protect the contents of your messages, text, and even files from being understood by anyone except their intended recipients. It can also be used to prove that a message came from a particular person and has not been altered.

In the past few years, end-to-end encryption tools have become more usable. Secure messaging tools like Signal (iOS or Android)—for voice calls, video calls, chats and file sharing— are good examples of apps that use end-to-end encryption to encrypt messages between the sender and intended recipient. These tools make messages unreadable to eavesdroppers on the network, as well as to the service providers themselves.

With that said, some implementations of end-to-end encryption can be difficult to understand and use. Before you begin using end-to-end encryption tools, we strongly recommend taking the time to understand the basics of public key cryptography.

The type of encryption we’re talking about in this guide, which end-to-end encryption tools rely on, is called public key cryptography, or public key encryption. To read about other types of encryption, check out our What Should I Know About Encryption? guide.

Understanding the underlying principles of public key cryptography will help you to use these tools successfully. There are things that public key cryptography can and can’t do, and it’s important to understand when and how you might want to use it.

What Does Encryption Do? Anchor link
Here’s how encryption works when sending a secret message:

A clearly readable message (“hello mum”) is encrypted into a scrambled message that is incomprehensible to anyone looking at it (“OhsieW5ge+osh1aehah6”).
The encrypted message is sent over the Internet, where others see the scrambled message, “OhsieW5ge+osh1aehah6”
When it arrives at its destination, the intended recipient, and only the intended recipient, has some way of decrypting it back into the original message (“hello mum”).
Symmetric Encryption: A Story of Passing Secret Notes with a Single Key Anchor link
Julia wants to send a note to her friend César that says “Meet me in the garden,” but she doesn’t want her classmates to see it.