Quantum Computing Isn't Just Coming for Bitcoin—It Threatens Messaging Apps Too
Quantum computing poses an imminent threat to encrypted messaging systems such as Signal and Threema, potentially allowing adversaries to break encryption that is currently secure against classical computers. Researchers highlight the risk of "store-and-forward" or "harvest now, decrypt later" attacks, where encrypted messages intercepted today could be decrypted in the future using quantum computers. This threat is seen as more immediate for messaging apps than for cryptocurrencies like Bitcoin, as past communications can be vulnerable retroactively. IBM, Signal, and Threema are collaborating to redesign messaging protocols to be quantum-resistant, with Signal already implementing post-quantum cryptography upgrades such as PQXDH and SPQR. Threema is working to integrate quantum-safe algorithms like ML-KEM. These upgrades also focus on protecting group chat metadata, with significant challenges around efficiency and bandwidth. Although practical quantum computers capable of breaking current encryption do not yet exist, rapid advances are accelerating preparations to safeguard sensitive communications against future quantum threats.
