In a report published on January 15, 2026, Citigroup warns that the window to prepare for so-called Q-Day, the hypothetical moment when quantum computers have the ability to crack the codes of today’s digital systems, may be narrowing.
The report, titled “Quantum Threats: A Trillion-Dollar Race for Security,” suggests that we are no longer preparing for that tipping point solely around when it will arrive, but rather when it will arrive. The cost and complexity of migrating your current infrastructure to post-quantum cryptography. Citi estimates that the transfer could exceed $1 trillion, based on global Y2K spending, or $600 billion to $1.1 trillion in current values.
Similarly, financial institutions The probability of Q-day occurring before 2034 is 19% to 34%Meanwhile, by 2044, estimates increase to a range of 60% to 82%. At the same time, prediction markets like Karsi put the probability of a useful quantum computer around 40% by 2030.
For Citi, the most immediate risk is not a direct attack in the future, but a model known as “save now, decrypt later.” Malicious attackers can store encrypted information today and store it for the following purposes: Decipher if enough quantum capacity exists.
It is noteworthy that in the case of cryptocurrencies, the report claims that risks vary depending on the design of each network. In Bitcoin (BTC), Approximately 25% of coins have potential risk Because their public keys are already published on the chain. In the case of Ethereum, Estimate exceeds 65% of current supplyMeanwhile, at Solana, the exhibition will cover almost all assets in circulation.
Finally, Citi also emphasizes that the transition will not be immediate or uniform. The bank notes that regulators have already begun defining post-quantum cryptographic standards, and some governments have set transition targets for critical systems by 2030 and 2035. The challenge adds: It’s not about not having a solution, it’s about implementing it at scale.
This analysis is partially consistent with recent valuations within the Bitcoin ecosystem. As reported by CriptoNoticias, a report by cybersecurity startup Project Eleven published in May stated: Q-Day could happen as early as 2030 Up to 6.9 million BTC, approximately 33% of the total supply, was compromised, especially those related to old reused addresses and visible public keys.
Nevertheless, Opinions continue to be divided on the ground.. While reports from Project Eleven, City, and others claim that the adaptation period could be shortened to this decade, Bitcoiner ecosystem players such as Adam Back, Samson Moh, and developer March believe it will still be years before we see quantum computers capable of cracking elliptic curve cryptography in real-world scenarios.
Much of the discussion so far has focused on whether Q-day will arrive within the next decade or beyond. City shifts focus to another issue. How much will it cost to adapt financial and technological systems and decentralized networks before that moment occurs? If the transition does indeed turn into a multi-year, multi-trillion dollar race, the real risk may not be the arrival of Q-day; Time is running out to migrate.
(Tag Translation) Bitcoin (BTC)
