WhatsApp completes end-to-end encryption.

WhatsApp is updating its messenger app so that every text and voice call on one of the world’s most popular apps will be protected with strong encryption – potentially putting millions more conversations outside the purview of authorities.

All of WhatsApp’s 1 billion users, when running the latest version of the app on iPhone, a Google Android device, Nokia or Blackberry, will send and receive messages, attachments and voice calls that engineers say can only be deciphered by the intended recipient, said Moxie Marlinspike, an encrypted messaging developer at Open Whisper Systems, whose technology forms the backbone of WhatsApp’s encryption.

This is what you see after both contacts use an updated version.

This is how it looks like when using an older version.

 This means WhatsApp shouldn’t be able to facilitate a wiretap of the contents of users’ messages, even if faced with a court order. It’s unclear if the company will be able to help authorities intercept data on when they use WhatsApp or with whom they communicate.

Additionally, WhatsApp will take the unusual step for a consumer app of notifying users if messages are encrypted, Marlinspike said.

If several users are trading texts in a group message and one of the users is running an older version of the app that doesn’t support encrypted group messages, the others will be able to tell which person is causing the session to remain unencrypted.

While the WhatsApp news may seem timely in light of the recent high-profile battle between Apple and the FBI over an encrypted iPhone, the company has spent 18 months discreetly expanding encryption throughout its service.