The quantum threat to encrypted communications
Quantum computing has been seen as a future issue for Bitcoin for years. But researchers now say encrypted messaging platforms could face more immediate risk. The problem is not only breaking current encryption, but also so-called store-and-forward attacks.
Basically, someone could record encrypted messages today, save them, and then decrypt them later when quantum computers become powerful enough. This is different from the situation with Bitcoin, where transactions take place in real time. For messaging, there is a lingering threat that past conversations could be revealed years from now.
Cryptography researcher Ethan Heilman pointed out that we’ve seen intelligence cases where communications were recorded decades ago and disrupted much later. “So for communications security,” he said, “there’s always the risk that the future decrypts the past, which we don’t have in Bitcoin.”
Messaging platforms take action
Signal and Threema are already working on this problem. In 2023, Signal introduced something called PQXDH to protect new sessions against these harvest-now-decrypt-later attacks. Then, in 2025, they added upgrades to the SPQR protocol to extend this protection to in-progress messages, calls, and media.
Threema is working with IBM’s cryptography team to explore integrating the ML-KEM algorithm into its system. ML-KEM is an approach standardized by NIST that is claimed to be quantum-resistant.
The work is not just about the content of the message itself. Researchers are also looking at protecting metadata: information about who is in group chats, when messages are sent, that sort of thing. This metadata can be just as revealing as the actual messages.
Technical challenges
An interesting problem the researchers faced was that of bandwidth. When they tried to adapt Signal’s existing protocol to be quantum-safe, they discovered that simply replacing current components with quantum-resistant versions would increase Signal’s bandwidth requirements by up to a hundred times.
This isn’t really practical for a messaging app that people use on their phones. So they had to rethink things from the ground up, focusing on speed and efficiency of communication. It’s not just about making things secure, it’s also about making them usable.
The IBM report states that it is virtually impossible to break current encryption with conventional supercomputers unless you have “a billion years to kill.” But quantum computing could radically change that timeline.
Why it matters now
Heilman mentioned that we have seen senior US national security officials use Signal for sensitive discussions. There was this 2025 incident in which Defense Secretary Pete Hegseth and others were using missing Signal messages on personal devices. When government communications are involved, the stakes become higher.
Most researchers still believe that machines capable of attacking Bitcoin are still far away. But the pace of development of quantum computing has accelerated. Experiments from IBM, Google and Caltech have improved stability, scaling and error correction.
“As soon as the threat becomes more real,” Heilman noted, “things move faster.” This is one of those situations where you don’t want to wait until there’s a real problem to start working on solutions. By then, it may be too late for messages already recorded and stored.
The ongoing work between IBM, Signal and Threema aims to get a head start. They are trying to build systems that will remain secure even as quantum computers become more powerful. It is preventative medicine for digital communications.
I think what’s interesting here is how different technologies face different timelines in the face of the quantum threat. For Bitcoin, it appears there is more time to prepare. For messaging, the risk seems more immediate because of the way messages can be stored and attacked later. Different problems require different solutions, even if they both deal with the same underlying advances in quantum computing.
