What to Know
- Quantum computing researchers at Alice & Bob estimate that a future machine with about 30,000 physical qubits could crack the cryptography protecting Bitcoin wallets in roughly 62 minutes.
- The estimate centers on 29,588 physical qubits, a level roughly 17 times lower than Google’s March estimate of fewer than 500,000 physical qubits, though the models use different assumptions and hardware designs.
- The attack window would still be too slow to reliably target transactions before confirmation because Bitcoin’s average block time is 10 minutes.
- More than six million bitcoins are held at addresses with exposed public keys, which could give a future attacker more time to derive private keys.
- Alice & Bob researchers stress that the findings are theoretical, but they argue that migration toward quantum-resistant security should begin now because network-wide upgrades could take years.
- The research uses Shor’s algorithm, a quantum method that could allow sufficiently powerful machines to solve cryptographic problems impractical for conventional computers.
- The company expects hardware improvements and declining resource requirements to converge in the early 2030s, increasing pressure on Bitcoin developers to plan ahead.
Quantum Research Sharpens Focus on Bitcoin Security
Bitcoin’s long-running quantum security debate has gained new urgency after researchers at quantum computing firm Alice & Bob estimated that a future quantum computer with about 30,000 physical qubits could break the cryptography protecting bitcoin wallets in roughly 62 minutes. The finding does not mean Bitcoin is under immediate attack, and the researchers describe the scenario as theoretical. Still, the estimate narrows the perceived gap between today’s quantum hardware and the kind of machine that could threaten older or exposed wallet structures.
FXCOINZ market coverage views the development as significant because Bitcoin’s security model depends on cryptographic assumptions that have remained practical against conventional computing. A sufficiently capable quantum computer, however, could change the threat landscape by using different computational principles. The Alice & Bob estimate places the required machine size at 29,588 physical qubits, far below prior models that had suggested substantially larger systems would be needed.
The comparison with Google’s March estimate is central to the market reaction. Google estimated that a future quantum computer would need fewer than 500,000 physical qubits to crack Bitcoin’s cryptography, down from earlier estimates in the millions. Alice & Bob’s new estimate is roughly 17 times lower than Google’s figure, although the two studies are not direct like-for-like comparisons because they rely on different hardware designs and assumptions. Even with that caveat, the reduced hardware requirement is likely to add pressure on developers and long-term holders to consider migration planning before the risk becomes operational.
Why Exposed Public Keys Matter
The most immediate theoretical concern is not every bitcoin wallet, but bitcoin held at addresses whose public keys have already been exposed. A public key is used by the Bitcoin network to verify that a transaction has been authorized without revealing the private key that controls spending. In normal conditions, this separation allows users to transact securely. In a future quantum scenario, however, a powerful machine could potentially work backward from an exposed public key to recover the corresponding private key and move the coins.
More than six million bitcoins are held behind exposed public keys, making that pool a key focus for quantum-risk discussions. The distinction matters because some addresses reveal public keys only when coins are spent, while others already have public keys visible on-chain. For coins sitting behind exposed public keys, an attacker would not need to wait for a fresh transaction to appear. That could give a future adversary more time to run an attack than the short window available for pending transactions.
The estimated 62-minute attack time is therefore both alarming and limited. It is alarming because it suggests a path by which exposed wallets could become vulnerable if quantum machines reach the required capability. It is limited because it is longer than Bitcoin’s average block time of 10 minutes, making it too slow to reliably intercept and steal funds from a normal transaction before confirmation. That timing issue is critical for assessing practical risk, since Bitcoin transactions generally become harder to reverse or exploit once confirmed.
Pending Transactions Face a Different Risk Profile
Bitcoin faces two broad quantum-risk categories: coins in pending transactions and coins held at addresses with exposed public keys. Pending transactions offer a short attack window because an attacker would need to derive the private key and broadcast a competing transaction quickly enough to beat confirmation. With an average block time of 10 minutes, the Alice & Bob estimate of roughly 62 minutes would not be fast enough for a reliable mempool attack under the assumptions presented.
That does not eliminate the risk entirely. Alice & Bob senior cryptanalyst Dahmun Goudarzi said the team had not yet completed calculations on whether adding more qubits could reduce the attack time below 10 minutes. He also noted that there is no architectural floor, leaving open the possibility that different designs, greater resources, or future optimization could narrow the time needed. He said further work could produce estimates comparable to Google’s earlier research, which modeled an attack taking about nine minutes.
For market participants, that uncertainty is the key issue. The current theoretical estimate does not imply that Bitcoin transactions are presently vulnerable to a known, practical quantum attack. But it does suggest that improvements in architecture and resources could matter as much as raw qubit counts. If future systems become more efficient, the practical timeline for defensive migration may shrink faster than many holders expect.
Shor’s Algorithm and the Quantum Threat
The research relies on Shor’s algorithm, a quantum computing method that could allow sufficiently powerful machines to solve mathematical problems that conventional computers cannot crack in a practical amount of time. Bitcoin’s cryptographic security relies on problems that are easy to verify but extremely hard to reverse using ordinary computing. Shor’s algorithm is important because it offers a theoretical route for a quantum computer to reverse certain cryptographic relationships that classical computers cannot feasibly break.
A qubit is the basic unit of quantum information. Unlike a classical bit, which can be either 0 or 1, a qubit can represent a combination of 0 and 1 states. That property is part of what gives quantum machines potential advantages in specific computational tasks. The practical challenge is building machines with enough reliable physical qubits to run complex algorithms at scale while managing errors and maintaining stability.
Alice & Bob’s model is notable because it suggests a lower physical-qubit requirement for a Bitcoin key-breaking attack than earlier expectations. Lower requirements do not automatically mean such a machine is imminent, but they do alter the planning assumptions around long-term security. If fewer physical resources are needed than previously believed, the timeline for preparing quantum-resistant upgrades could become more pressing.
Migration Could Take Years
Goudarzi said it is of utmost importance that migration starts now, noting that the task could be hard and long. That warning reflects Bitcoin’s decentralized structure. Unlike a centralized platform that can push a security update across all accounts, Bitcoin requires broad agreement among developers, node operators, miners, wallets, exchanges, custodians, and users. Any transition to quantum-resistant signatures would need careful design, testing, and adoption.
The difficulty is not only technical. Migration would also involve user behavior. Coins held in older address formats or at exposed public keys may need to move to safer structures once the network supports them. Some owners may be inactive, unaware, or unable to access their coins. That creates a practical challenge because quantum risk is unevenly distributed across the network. Active and informed users could migrate early, while dormant holdings could remain vulnerable.
The researchers expect hardware improvements and declining resource requirements to converge in the early 2030s. That timeline is not a prediction that an attack will happen then, but it frames why the issue is gaining attention. If network-wide changes can take years, waiting until threatening hardware clearly exists could leave too little time for a smooth transition.
Market Implications for Bitcoin Holders
For bitcoin holders, the findings are best understood as a strategic security warning rather than an immediate market emergency. The research does not indicate that current quantum hardware can steal bitcoin, nor does it show that all wallets are equally exposed. It does, however, reinforce the importance of address hygiene, protocol research, and long-term upgrade readiness.
Technical traders and long-term investors may interpret the news differently. Short-term price action often reacts more strongly to liquidity, macroeconomic conditions, exchange flows, and sentiment than to distant cryptographic risks. Long-term allocators, however, may pay closer attention to whether Bitcoin’s developer ecosystem can respond proactively. A credible migration path to quantum-resistant security could reduce uncertainty, while delays could keep the issue alive as a recurring risk theme.
FXCOINZ sees the broader question as one of governance and preparedness. Bitcoin has survived many security debates because its community tends to move carefully and conservatively. That caution can be a strength when protecting a high-value decentralized network, but it can also slow urgent upgrades. Quantum-resistant migration may test whether Bitcoin can balance caution with timely action as research models evolve.
Why the Findings Remain Theoretical
The Alice & Bob findings remain theoretical because they describe what a future quantum computer could potentially do if it had the necessary architecture and resources. The model does not claim that such a machine exists today. It also depends on assumptions about hardware design, error handling, and algorithm implementation. Those assumptions can change as researchers refine their methods.
The difference between theoretical vulnerability and practical exploitability is important. Cryptographic systems can be mathematically vulnerable to a future class of machines long before those machines become available. That is why security planning often begins before a direct threat is observed. In Bitcoin’s case, the value secured by the network and the visibility of its public ledger make advance planning especially important.
The key takeaway is not that Bitcoin’s cryptography has suddenly failed. Rather, the cost and scale of a potential future attack may be lower than previously expected under the Alice & Bob model. That makes quantum resistance less of a distant academic concern and more of a strategic item for developers, custodians, and holders with long-term exposure.
Frequently Asked Questions (FAQs)
What did Alice & Bob estimate about Bitcoin and quantum computing?
Alice & Bob researchers estimated that a future quantum computer with about 30,000 physical qubits could crack the cryptography protecting bitcoin wallets in roughly 62 minutes. Their more precise estimate is 29,588 physical qubits, although the scenario remains theoretical.
Does this mean Bitcoin can be hacked today?
No. The findings describe a theoretical future attack using quantum hardware that is not stated to exist today. The research highlights a potential future risk and increases pressure for planning around quantum-resistant security.
Why are exposed public keys a concern?
An exposed public key could allow a sufficiently powerful quantum computer to work backward and derive the corresponding private key. That private key would allow an attacker to spend the coins controlled by that address.
How many bitcoins may be affected by exposed public keys?
More than six million bitcoins are held at addresses with exposed public keys. Those coins are the main focus of this risk because an attacker could have more time to target them than coins involved only in pending transactions.
Can a 62-minute attack steal bitcoin from normal pending transactions?
The estimated 62-minute attack would be too slow to reliably target transactions before confirmation because Bitcoin’s average block time is 10 minutes. Researchers have not yet completed calculations on whether adding more qubits could reduce the time below that level.
How does this compare with Google’s estimate?
Google estimated in March that a future quantum computer would need fewer than 500,000 physical qubits to crack Bitcoin’s cryptography. Alice & Bob’s estimate of 29,588 qubits is roughly 17 times lower, though the studies use different hardware designs and assumptions.
What is Shor’s algorithm?
Shor’s algorithm is a quantum computing method that could allow sufficiently powerful quantum computers to solve certain mathematical problems that conventional computers cannot crack in a practical amount of time. It is central to concerns about quantum attacks on existing cryptographic systems.
Why could migration to quantum-resistant security take years?
Bitcoin is decentralized, so major security upgrades require careful design, testing, and broad adoption across developers, wallets, exchanges, custodians, node operators, miners, and users. Moving vulnerable coins and updating signature systems could be a long and complex process.
When do researchers expect the risk to become more relevant?
Alice & Bob expects hardware improvements and declining resource requirements to converge in the early 2030s. That expectation does not confirm an attack timeline, but it underscores why researchers are urging preparation now.