WhatsApp begins beta for multi-device use while retaining encryption

WhatsApp has launched a beta that allows users to use the service on multiple devices at the same time without the need for a smartphone connection. The end-to-end encryption remains intact, according to parent company Facebook.

WhatsApp is starting a public, but limited beta of the new feature, parent company Facebook writes. The new feature allows users to use WhatsApp on up to four other devices in addition to the smartphone. That shouldn’t be any other phones. WhatsApp can therefore also be used when the original phone is turned off, something that was not possible until recently. The feature does work as it does now, syncing messages, contacts, and favorite messages or archived chats.

According to WhatsApp, it had to ‘completely rethink WhatsApp’s architecture’. With that new architecture, the end-to-end encryption of the service will remain. For this, all devices now get their own identity key, instead of there being one key that is created on the active device. The WhatsApp server that traffic passes through keeps track of which identities a user has on his account. This list is requested from the server when a message is sent.

The messages are then synchronized by sending an encrypted blob through WhatsApp’s servers. These can only be opened with the keys on the connected computers, after which they are removed again and the connected device retrieves the data locally again. WhatsApp settings, such as user status or which chats are on mute, require a constant connection to the WhatsApp servers.

A number of new security measures have been implemented to prevent, for example, a man-in-the-middle attack from being carried out. For example, WhatsApp has expanded the security codes that appear when a user changes device. From now on, it will show all other users’ devices. WhatsApp will also get Automatic Device Verification, which will only require them to re-authenticate devices when re-registering their account.