Interoperability, or the ability for users to communicate between social media or messaging platforms, is a key part of Europe’s landmark DMA legislation. However, as with much of the bill, it remains unclear whether the mandate is needed, whether it will work, and what the consequences of imposing it will be.

Supporters say consumers will benefit from increased choice and competitors will gain an opportunity to build out innovative functions. Consumers are hesitant to switch to new apps, even if they offer superior functionality, for fear of losing the ability to communicate with large numbers of their friends and contacts who stay behind on larger, entrenched apps. European policymakers believe that the apps with the largest number of users benefit from network effects and enjoy an unfair advantage. By imposing interoperability, they aim to level the playing field.

Critics fear the new rules discriminate against American tech companies, will damage privacy by sacrificing encryption, and present security risks. It remains unclear, too, whether small messaging apps must sacrifice their privacy protections to link up with the dominant apps.

Interoperability itself is not a new concept. In traditional telephony, phone calls work among different operators. Networks adhere to a common protocol standard. In contrast, messaging services do not speak the same language. They communicate app to app. Many phones contain multiple messaging apps – switching is easy and without cost.

The DMA, approved this month, mandates interoperability among the products of the largest tech firms (Facebook, Google, Microsoft, Amazon, and Apple). Under a leaked version of the final text, the rules will be applied to one-to-one messaging and file transfer initially, then to group messaging in two years, and finally to one-to-one or group video calls in four years.

Technically, this is feasible. Gatekeepers could open up their software links, called application programming interface (APIs). Apps would then connect from competing apps.

That’s where the difficulties begin. As part of an essential privacy protection, most messaging apps offer end-to-end encryption. In order to make messages interoperable, the content must be decrypted. Theoretically, it could be re-encrypted in the receiving apps language. Some experts say this is impossible

“Trying to reconcile two different cryptographic architectures simply can’t be done,” asserts Steven Bellovin, a computer science professor at Columbia University. “A design that works only when both parties are online will look very different than one that works with stored messages… How do you make those two systems interoperate?”

Even the measure’s supporters acknowledge that such encryption seems difficult to achieve. We “had some doubt in particular on encryption,” admitted Andreas Schwab, the key European parliamentarian behind the DMA in a podcast.  “The European Parliament never wanted to open services that are not perfectly encrypted.”

Yet, other experts believe a solution can be found. Matthew Hodgson, of the open source software NGO Matrix, has charted a potential path forward. “The bottom line is, we should not be scared of interoperability, just because we’ve grown used to a broken world where nothing can interconnect,” Hodgson says. “There are tractable ways to solve it in a way that empowers and informs the user – and the DMA has now given the industry the opportunity to demonstrate that it can work.”

Interoperability’s competitive impact is hard to analyze. While gatekeepers (the term used in the DMA for large tech firms) will be forced to open up, those run by non-gatekeepers such as Telegram will not face a similar obligation. Will the gatekeepers be allowed to access their competitor’s subscriber base? Will the small apps want to lose their privacy protection in order to connect calls with the big apps?

Only time will tell if industry is able to build a privacy-protecting solution and answer these questions. The DMA doesn’t include technical details on how interoperability would work.  It will be critical that a diverse set of players engage in the standardization process to find a solution. Expect a follow up in a few years time to see if all the effort produces positive – or negative – change.

Giovanni Tricco is an intern at CEPA’s Digital Innovation Initiative.

Alexander Wirth is a Program Officer for CEPA’s Digital Innovation Initiative.