Long confined to speculation on bitcoin, quantum computing is now entering a much more sensitive field: that of encrypted messaging. Behind the debate on blockchain security, another, more immediate threat is taking shape: that of private data intercepted today, then decrypted tomorrow. Researchers and industrialists are warning of this shift, which shifts the front line towards tools like Signal or Threema.
In brief
- Quantum no longer threatens only Bitcoin, but also encrypted messaging.
- Data captured today could be deciphered later.
- Signal and Threema appear to be more exposed targets in the short term.
- IBM and several players in the sector are already working on post-quantum protections.
A more immediate threat to Signal than to bitcoin
Quantum computing is often presented as a threat to bitcoin. Indeed, cryptographer Ethan Heilman explains that the short-term risk would be greater for applications like Signal than for bitcoin, not because a quantum attack would already be possible, but because certain communications can be intercepted today, preserved, then attacked later.
The topic is no longer just the future strength of a decentralized monetary network, but the potential vulnerability of private conversations already exchanged. In this context, we recall that Signal and Threema, launched in 2014 and 2012 respectively, are based on end-to-end encryption and store the keys on user devices. The issue therefore concerns sensitive data likely to be collected today while awaiting more advanced computing capabilities.
Ethan Heilman formulates the alert in direct terms. He declared : “the short-term threat is much greater for an application like Signal than for bitcoin, due to attacks consisting of storing encrypted messages today to try to exploit them later”.
He adds: “In theory, someone could record communications today, then attack them later once they have a quantum computer”.
- The reasoning is based on the logic of “collect today, decipher later”. Even without a quantum computer operational yet to break these systems, the value of an interception may already exist. Malicious actors could hoard data by betting on future decryption capabilities. This is what makes messaging more exposed in the short term;
- Encrypted messaging is used by individuals, journalists, governments and political leaders. This gives this alert a broader scope than a simple technical debate on bitcoin and blockchains.
IBM, Signal and Threema move to the adaptation phase
The second dimension does not relate to the alert itself, but to the responses already initiated. In a post published on March 9, 2026, IBM Research noted that its researchers are working with Signal and Threema to prepare communication systems resistant to future quantum machines.
IBM recalls that in 2024, NIST published a first set of three post-quantum cryptography standards. The group also explains that the subject is not limited to message encryption, but it also concerns the finer bricks of the protocol, such as certain metadata linked to discussion groups.
Signal had already started this transition. In a post dedicated to PQXDH, the company explains having added a post-quantum mechanism to protect new discussion sessions against the risk of future decryption. Then, on October 2, 2025, Signal announced SPQR, presented as a new step intended to strengthen the protocol's resilience against quantum threats while retaining guarantees of persistent privacy and security after compromise.
IBM adds that adapting these protections on a large scale poses a very concrete efficiency problem. A simple transposition of current components to post-quantum equivalents could result in “up to a hundred times increase in Signal bandwidth”. It is this observation that pushes teams to review protocols in depth.
As Signal, Threema and IBM accelerate into post-quantum, the question arises: what if quantum fear was just an excuse to rethink communications security more broadly? Behind the technological alert, it is perhaps the entire architecture of digital confidentiality which is entering a new phase.
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