When you’re using WhatsApp your messages are encrypted end-to-end, which means prying eyes can’t easily see what’s in them as they travel back and forth. However, if you keep a backup stored in the cloud, authorities can use a search warrant to have Google Drive or iCloud hand over access to the data. But WABetaInfo has reported previously that WhatsApp is working on the technology to independently encrypt your backups in the cloud, and says that in the most recent beta update on Android (18.104.22.168), the system has been enabled.
Opting in should keep your chat history and media securely backed up, with the significant caveat that if you forget your passcode / lose the 64-digit recovery key, then they’ll be locked away permanently — even WhatsApp can’t help you get in. If you’re OK with being on your own in that respect, then all you need to do is get in the beta test group or wait for this to be available to everyone.
The Facebook-owned service is also testing a version of the software that works across multiple devices, maintaining end-to-end encryption whether or not you have a phone involved. If you’re in the beta, check your version carefully, as posts on social media suggest the closed encryption tests are expanding to include more people.