Ethereum co-founder and ConsenSys CEO Joe Rubin has once again sparked a controversial debate about Bitcoin's long-term safety. During the discussion, he warned that Bitcoin could face existential problems in the future. In particular, he mentioned the idea of a so-called Q-day, when quantum computers would be able to break modern codes. Although Rubin emphasized that the threat is not imminent, he made it clear that it would be a mistake to treat it as irresponsible. It is understandable for him to worry today and not take action for the future.
🔥 Joe Rubin warns about Bitcoin quantum risks
Joe Rubin hinted at a “Q-day” when cryptography could be challenged by quantum computers, saying Bitcoin could face an “existential problem.”
He added that even if that day has not yet come, “there is reason to be concerned” about this risk. pic.twitter.com/PFF6Nx6oIV
— Coin Bureau (@coinbureau) February 11, 2026
What Bitcoin really means by Q-day
Bitcoin is also based on the encryption provided by ECDSA to secure wallets and transactions. Under normal circumstances, this system is very secure. However, quantum computers introduce new variables. With highly developed quantum computers, it would theoretically be possible to use Scholl's algorithm to deduce the private key based on the public key. If this happens, there is a possibility that attackers can access Bitcoin addresses, which have a huge amount of value, because there are addresses surrounding unspent coins. As a result, Bitcoin's fundamental security assumptions will be put to the test for the first time since its inception.
Nevertheless, there is still a long way to go before current technology poses an immediate threat. The most sophisticated quantum machines in the world today have just over 1,000 qubits. By comparison, breaking Bitcoin's encryption requires millions of stable, error-corrected qubits. Estimates consistent with NIST research suggest that such capabilities could take 10 to 20 years. Therefore, this threat is theoretical and not real. Nevertheless, Rubin says that long-term systems like Bitcoin require planning decades in advance.
Why the risks are still years away
Reactions to Rubin's remarks have been sharply divided. On the other hand, this warning has been ignored by critics, who say that Ethereum has caused fear, uncertainty, and doubt. They argue that Bitcoin has already demonstrated the ability to change through upgrades and consensus. On the contrary, some developers and researchers believe that they are preparing. They point out that post-quantum cryptography, such as lattice-based signature schemes, already exists. It is worth noting that Ethereum researchers are working on these alternatives. This contrast highlights the philosophical distinction between proactive and reactive security models.
It's not just a Bitcoin issue. Systems based on classical cryptography have the same long-term vulnerabilities. Nevertheless, based on Bitcoin's size, it is the most notable target. Additionally, this discussion signals broader changes in cryptocurrencies. Security discussions no longer revolve around hacking and exploits. Instead, we are growing to be future-proof for technologies that are not yet fully developed. This change may impact protocol development across the industry.
Why this discussion matters beyond Bitcoin
Joe Rubin isn't saying Bitcoin is broken today. Instead, he urges the market to look to the future. Quantum computing won't come soon, but its impact will be far-reaching. It is still unclear how Bitcoin will be upgraded to post-quantum resilience, or how it will withstand other forms of resilience. What is understandable is that the Q-day debate is no longer a fringe idea. They are becoming part of the long-term roadmap for cryptocurrencies.
