to keep your messages private.

It's available on both mobile and desktop,

but for this video,

we'll be focusing on the mobile app.

With Signal, the only people who can see

the messages you send

are you and the person who receives them,

because they're encrypted.

However, Signal's messages are only secure

if both the sender and receiver are on the app.

You can download Signal for iPhone or Android for free.

We'll be using an iPhone for this tutorial.

First, go to the Apple store and search for Signal.

Once you find it, tap on "GET" or "Download."

Once you've downloaded it,

you can sign up with your cellphone number.

The app can automatically detect

which of your contacts also use Signal,

and you can always click on "Invite Friends to Signal"

to choose more people.

Chats look nearly identical to iMessage,

with similar features, like sending texts and photos.

You can also make secure voice calls over a data network.

Each person is shown a random pair of words

that they can use to verify the call is secure.

In this case, you tell the person that you're calling

"chisel" and they'd reply "sociable" for verification.