Everyone’s worried that the UK Online Safety Bill and the EU Child Sex Abuse Regulation will put an end to end-to-end encryption. But might a law already passed by the EU have the same effect?

The Digital Markets Act ruled that users on different platforms should be able to exchange messages with each other. This opens up a real Pandora’s box. How will the networks manage keys, authenticate users, and moderate content? How much metadata will have to be shared, and how?

In our latest paper, One Protocol to Rule Them All? On Securing Interoperable Messaging, we explore the security tensions, the conflicts of interest, the usability traps, and the likely consequences for individual and institutional behaviour.

Interoperability will vastly increase the attack surface at every level in the stack – from the cryptography up through usability to commercial incentives and the opportunities for government interference.

Twenty-five years ago, we warned that key escrow mechanisms would endanger cryptography by increasing complexity, even if the escrow keys themselves can be kept perfectly secure. Interoperability is complexity on steroids.