Now you can use WhatsApp on four devices. How to participate in the beta

After years of waiting, finally you will be able to use WhatsApp on multiple devices without connection to the smartphone. The messaging company has announced the launch of a beta version, which will allow to extend the use of WhatsApp to a maximum of four devices that will be completely independent from the smartphone.

Although the request had become pressing by now, and although the competition had already implemented the function years ago, to achieve this goal WhatsApp had to completely rethink its architecture.

The launch of the first public beta was also an opportunity to take a look at the new architecture capable of maintaining end-to-end encryption despite data synchronization across all devices.

How to participate in the beta

To try out the new multi-device functionality, you can sign up for the beta via the WhatsApp support page. The company seems intent on working on a small group of testers, so registrations may close soon. The beta is available for Android and iPhone users with the latest version installed, including WhatsApp Business.

To join on Android you need to tap on the three dots and then on Connected devices> Multi-device beta version> Join the beta version.

On the iPhone the path is similar. After entering the WhatsApp settings you need to go to Connected devices> Multi-device beta version> Join the beta version.

From the same page, you can exit the beta program by tapping “Abandon beta version”.

The WhatsApp beta, while enabling multi-device management, does not include some features, including:

  • real-time location display in additional devices
  • the top block of chats on WhatsApp Web or WhatsApp Desktop
  • sending messages or calls from your connected device if the recipients have an older version of WhatsApp on their phone.

It will no longer be the smartphone that will take care of all the part relating to encryption

It is already possible to use WhatsApp on devices other than the smartphone: you can use the messaging program on a PC, as long as the device is connected to the smartphone. In this way, all operations related to encryption are delegated to the smartphone which must be constantly connected to the network.

The new architecture of WhatsApp eliminates this limit, while keeping the user’s data synchronized, safe and private but without it being stored on the WhatsApp servers.

The biggest novelty of the new architecture is that each device can count on its own identity key. In the past, every WhatsApp user was identified by a unique key.

In this way, simplifying, the WhatsApp server maintains a mapping between each person’s account and all device identities: when someone wants to send you a message, they get the device list keys from the server.

To avoid security problems related to this mechanism, each additional device must be authorized the first time it is used by the user, via a QR code. Biometric authentication is also provided for eligible phones. At any time, then, the user will be able to see the devices associated with his account.

An encrypted connection is established between all the sender’s and receiver’s devices

When two people exchange a message, an encrypted session is established between all the sender’s and the receiver’s devices. Each message is individually encrypted using the pairwise encryption session established with each device: messages are not archived on the server after delivery.

The history of messages and everything related to the application will be synchronized on all devices: when a paired device is connected, the primary device encrypts a group of messages from recent chats and transfers them to the newly connected device.

After the companion device has downloaded, decrypted, decompressed, and securely archived the messages, the keys are deleted. From then on, the companion device accesses the message history from its local database.

Only some information relating to contacts and chats will remain on the WhatsApp servers

Instead, the WhatsApp servers will store a copy of each application state that all of someone’s devices can access – adding new contacts, muted or archived chats, etc – which will then be passed from the phone to the associated devices periodically.

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