When the EU first announced that messaging apps may have to work together in early 2022, many leading cryptographers opposed the idea, saying it adds complexity and potentially introduces more security and privacy risks. Carmela Troncoso, an associate professor at the Swiss university École Polytechnique Fédérale de Lausanne, who focuses on security and privacy engineering, says interoperability moves could potentially lead to different power relationships between companies, depending on how they are implemented.
“This move for interoperability will, on the one hand, open the market, but also maybe close the market in the sense that now the bigger players are going to have more decisional power,” Troncoso says. “Now, if the big player makes a move and you want to continue being interoperable with this big player, because your users are hooked up to this, you’re going to have to follow.”
While the interoperability of encrypted messaging apps may be possible, there are some fundamental challenges about how the systems will work in the real world. How much of a problem spam and scamming will be across apps is largely unknown until people start using interoperable setups. There are also questions about how people will find each other across different apps. For instance, WhatsApp uses your phone number to interact and message other people, while Threema randomly generates eight-digit IDs for people’s accounts. Linking up with WhatsApp “could de-anonymize Threema users,” Weis, the Threema spokesperson says.
Meta’s Brouwer says the company is still working on the interoperability features and the level of support it will make available for companies wanting to integrate with it. “Nobody quite knows how this works,” Brouwer says. “We have no idea what the demand is.” However, he says, the decision was made to use WhatsApp’s existing architecture to run interoperability, as it means that it can more easily scale up the system for group chats in the future. It also reduces the potential for people’s data to be exposed to multiple servers, Brouwer says.
Ultimately, interoperability will evolve over time, and from Meta’s perspective, Brouwer says, it will be more challenging to add new features to it quickly. “We don’t believe interop chats and WhatsApp chats can evolve at the same pace,” he says, claiming it is “harder to evolve an open network” compared to a closed one. “The second you do something different—than what we know works really well—you open up a wormhole of security, privacy issues, and complexity that is always going to be much bigger than you think it is.”