The move comes after Facebook-owned WhatsApp turned on full end-to-end encryption earlier this month, bringing secure and private instant messaging into the mainstream.
The majority of IM apps have long encrypted the communications between users' devices and their own servers. However, in such a configuration, the service providers themselves can still read communications as they pass through their servers to get routed to the intended recipients.
End-to-end encryption systems like those implemented by WhatsApp and now Viber allow user devices to establish a secure communications channel directly, making it impossible for anyone else to see the unencrypted data.
This means that even if a provider's servers are breached by hackers, they won't be able to view unencrypted user communications. It also means that companies like WhatsApp and Viber Media will be unable to comply with law enforcement requests for the content of their customers' chats or audio calls.
Viber's end-to-end encryption feature is available in the application's latest version -- 6.0 -- for Android, iOS, PCs and Macs. It provides strong privacy and security for voice or video calls, text messages and videos and photos exchanged by users in both group and one-to-one conversations.
When end-to-end encryption is used Viber users will see a grey padlock in their chats and calls. When they verify the identity of their contacts and mark them as trusted, a green padlock will appear.
The authentication keys for the trusted contacts will be monitored and if they change at some point in the future, the padlock for those conversations will turn to red. This indicates either a possible impersonation attempt by a man-in-the-middle attacker or the fact that the contact has changed their primary phone.
The new Viber version also includes a "Hidden Chats" feature. This will allow users to hide specific conversations in their Viber apps and to protect them with a PIN or a fingerprint, in the case of iOS devices that have fingerprint sensors.
While Viber and WhatsApp are not the first messaging services to implement end-to-end encryption, they are certainly some of the largest ones. Until now, to benefit from this level of secure messaging on some platforms users had to install specialized IM apps and then convince their friends to use them as well.
With the barrier to end-to-end encryption lowered and the feature becoming a default in popular messaging apps a larger percentage of Internet communications will become inaccessible to law enforcement who are already complaining about the widespread use of encryption.