WhatsApp is the mobile messaging backbone of much of the global population, and all of its users just got an added layer of privacy protection.
On the WhatsApp blog, the Facebook-owned messaging app confirmed that end-to-end encryption for backed up chats in the cloud will roll out "slowly" to all of its two billion (!) users starting now. This was previously announced in September, but without a specific release date. All you need to do is have the latest version of the WhatsApp mobile app installed to get access to the feature.
Here's how it works: Let's say you're getting a new phone and want to keep some WhatsApp conversations that are stored locally on your current device around for future reference using the iCloud or Google Drive cloud backup that's already available in WhatsApp. Open the Settings menu, find the "Chat Backup" option in the Chats section, then tap "End-to-end Encrypted Backup." You'll be prompted to turn it on, and guided through the process of creating a custom password or a 64-digit key. Hit "Create" after that and watch the magic happen.
Of course, it's vital that you keep your password or key around so you can use it later. What this feature does is lock that cloud backup behind a layer of security that prevents both WhatsApp and any cloud service from accessing the messages or the key used to unlock them.
This closes a loophole that would have allowed governments to force cloud services to hand over backed up messages, notably in the wake of increased online surveillance laws in India. That country has the largest concentration of WhatsApp users in the world.
As always, if an app gives you the option to enhance privacy, you should probably use it.