You Can Now Turn Messages into Secret Code Using Emoji

Emoji are developing into their own language, albeit a sometimes impenetrable one. But they are about to become truly impenetrable. A new app from the Mozilla Foundation lets you use them for encryption.

The free web app, called Codemoji, lets users write a message in plain-text, then select an emoji “key” to mask the letters in that message with a series of emoji. To decrypt a message, the correct key must be entered in the app, turning emoji back into the alphabet.

So if you wanted to write:

We’re not in Europe anymore!

and used the Face Screaming in Fear emoji as a key, then the encrypted message would look like this:

Users can grab emoji-coded messages and share them with friends, who can then try to decrypt them by guessing at the correct key. You can decrypt my message here.

The encryption method is nothing sophisticated. It’s just an emoji-fied version of an ancient system, the Caesar cipher, named for Julius Caesar, who reputedly used it for secret messages. The original version substitutes each letter of the alphabet with another letter a certain number of positions away.

With Codemoji, the substitution is done with an emoji instead. A Caesar cipher is easy to crack with modern tools, as a computer can run through all the possible substitutions in a fraction of a second.

But the idea behind the Codemoji project is to increase awareness about how encryption works, because it’s being “threatened” by governments around the world, according to the Mozilla Foundation. The high-profile, high-stakes fight between Apple and the FBI was the latest example of the tensions around encryption and technology.