Can quantum computers break Bitcoin?

What Is Bitcoin?

Bitcoin is a cryptocurrency first proposed in a 2008 white paper published by the anonymous entity known as Satoshi Nakamoto. In 2009, the Bitcoin network officially launched, producing its first block—the Genesis Block. This technological breakthrough established the foundation for decentralized digital currency, fundamentally distinct from traditional financial systems.

Key Features of Bitcoin

Bitcoin's most significant feature is that it enables direct transactions between users without oversight from centralized authorities like central banks or governments. This decentralized system is powered by blockchain technology, which records all transaction data transparently and immutably. Bitcoin's supply is strictly limited to 21 million coins, making its scarcity a critical factor in its value.

Bitcoin secures transactions using public-key cryptography. By leveraging paired public and private keys, it ensures transaction validity and prevents unauthorized tampering. This cryptographic system makes it extremely difficult for third parties to forge transactions or illicitly transfer assets.

Initially, Bitcoin was traded only among tech enthusiasts. More recently, it has gained widespread attention as an investment asset and payment method. Today, Bitcoin is available on exchanges around the world, greatly enhancing its practical utility.

How Bitcoin Differs from Centralized Currencies

Bitcoin operates on fundamentally different principles than traditional centralized currencies. Fiat currencies (like the yen or dollar) are issued and managed by central banks or governments, with supply and interest rate policies set centrally. Bitcoin, on the other hand, has no central administrator; every network participant equally approves and verifies transactions.

Advantages of this decentralized system include:

• Rapid transactions: Without banks or payment intermediaries, transaction processing times are reduced. International transfers that take days through banks can settle in hours.
• Smoother cross-border payments: Bitcoin enables seamless transfers across borders, making it ideal for global commerce. Exchange and intermediary fees are also greatly reduced.
• Inflation resistance: With a fixed supply of 21 million coins, Bitcoin avoids the dilution caused by excessive issuance of fiat currencies. This scarcity is a key reason Bitcoin is often called "digital gold."

For these reasons, Bitcoin is regarded as an innovative alternative to traditional financial systems and is widely used by individuals and businesses for asset protection and efficient transactions.

What Are Quantum Computers?

Quantum computers represent a new generation of computing technology that leverages quantum mechanics to rapidly and efficiently solve problems that are difficult for conventional computers. Traditional computers use bits (0 or 1) to process data, while quantum computers use "qubits," which can simultaneously represent both 0 and 1 in a state called superposition. This enables parallel computation across multiple states.

Additionally, "quantum entanglement" allows multiple qubits to be strongly correlated, enabling complex problem-solving. With entanglement, information can be instantly shared among qubits, making it possible to perform calculations in minutes that would take traditional computers thousands of years.

Applications and Future Potential

Quantum computers are expected to revolutionize fields like machine learning, financial portfolio optimization, and chemical simulations. For example, they can accelerate drug discovery by simulating molecular behavior, analyze massive datasets to optimize supply chains, and improve complex weather forecasting and climate modeling.

In pharmaceuticals, quantum computers enable analysis of intricate molecular structures, significantly shortening drug development timelines. In finance, they can vastly improve risk analysis and portfolio optimization, allowing for more accurate investment decisions.

Current Challenges and Future Outlook

Quantum computers remain a developing technology that requires further research and innovation to reach full maturity. Key challenges include qubit error rates, stability, and the need for large-scale cooling infrastructure. Qubits are highly unstable and sensitive to environmental factors, so operation in ultra-low temperatures is necessary.

Even so, quantum computers offer the potential to execute calculations in minutes that would take conventional computers millennia, and their innovations are expected to reshape future industries.

As research advances, IBM has announced plans to launch quantum systems with 200 logical qubits and 100 million quantum gates by 2029. By 2033, IBM aims for systems with 2,000 logical qubits and 1 billion quantum gates. Microsoft is developing quantum computing through Azure Quantum, and Amazon has entered the field via AWS, fueling global R&D competition.

Can Quantum Computers Threaten Bitcoin?

Bitcoin uses cryptographic algorithms such as SHA-256 for mining. These algorithms are highly secure against classical computing, but they could be vulnerable to the immense processing power of quantum computers. In theory, quantum computers might decrypt private keys, compromising wallet and transaction security.

Quantum computers can solve complex mathematical problems much faster than traditional computers, potentially changing the distribution of mining power and undermining the decentralization of some cryptocurrencies. They may be able to break public-key cryptography and decrypt private keys, leading to security threats such as unauthorized access or theft of crypto assets.

Carlos Perez-Delgado, a lecturer at Kent University, stated that defending Bitcoin from quantum threats would require significant time and resources. He warned that a powerful quantum computer could fully control Bitcoin.

Research from Kent University suggests that mitigating quantum threats would require a protocol upgrade with 76 days of offline downtime. Alternatively, a more practical approach would dedicate 25% of servers to upgrades while continuing transactions and mining at reduced speed, resulting in roughly 10 months of downtime. Perez-Delgado stressed that tech companies must urgently address quantum computing risks:

The arrival of quantum computers will inevitably expose current cybersecurity systems to major risks.

Ponemon Institute estimates that one hour of downtime costs businesses $500,000; if Bitcoin were offline for 76 days, losses could reach $912 million.

With 275 million Bitcoin investors and no central administrator, implementing updates is extremely challenging. Blockchain updates require each transaction to be individually upgraded, and Bitcoin's slow processing speed makes this process even more complex. Technologies like "death throttling" can accelerate processing, but they may negatively impact user experience, much like prolonged downtime.

Countermeasures Against Quantum Computing

Major US cryptocurrency exchanges are considering the following responses to quantum computing threats:

• Quantum-resistant cryptography: Developers are pursuing new encryption technologies designed to withstand quantum computing. These methods are based on mathematical problems that remain difficult even for quantum computers.
• Quantum-resistant currencies: New cryptocurrencies are being discussed that are built with quantum attack resistance in mind from the outset.

Are Satoshi's Bitcoins at Risk? Experts Flag Security Concerns

Emin Gün Sirer, founder and CEO of Ava Labs, recently proposed freezing an estimated 1.1 million BTC held in Satoshi Nakamoto's wallet. He pointed out vulnerabilities in the early Pay-to-Public-Key (P2PK) format used by initial wallets, warning that quantum computing could exploit these flaws.

Sirer argues that quantum computers threaten cryptographic methods like RSA and elliptic curve cryptography, but have limited impact on one-way hash functions, so current risks to cryptocurrencies are relatively contained:

Quantum computing speeds up specific computations, but its ability to reverse one-way hash functions used in cryptocurrencies is limited. Some platforms offer only a brief window for quantum attacks, making successful exploits more difficult.

The Early P2PK Format and Quantum Computing Risks

Satoshi Nakamoto's early wallets used the P2PK format, which exposes public keys directly. While this format is no longer used in modern Bitcoin wallets or systems like Avalanche, it was common in Bitcoin's early days. Sirer maintains that coins using the P2PK format should be frozen before quantum computing becomes widespread:

Coins mined in Satoshi's early days could become prime targets for attackers. Before quantum computing threats materialize, it may be necessary to establish procedures to freeze all coins based on P2PK UTXOs.

The key issue is that public keys can be directly obtained from addresses. Since all Bitcoin transactions are public, anyone can extract a public key from a P2PK address. If quantum computers are able to derive private keys from public keys, coins at those addresses could be vulnerable to theft.

P2PKH addresses are based on a hash of the public key, which is only revealed when coins are spent. If a transaction has never occurred, the private key is safe. Once a transaction is made, the public key is exposed and the address is considered "used." While most wallets prevent address reuse, not all users follow these safeguards.

Sirer's proposal is part of ongoing discussions on strengthening crypto security and has drawn attention as a countermeasure to the impact of quantum computing advances.

How Much Bitcoin Could Be Stolen by Quantum Computers?

If quantum computers can derive private keys, all coins stored in P2PK addresses and reused P2PKH addresses would be vulnerable to attack.

During Bitcoin's first year, P2PK addresses dominated, and about 2 million BTC remain in these addresses today. After P2PKH was introduced in 2010, most coins migrated to that format. However, reused P2PKH addresses currently hold about 2.5 million BTC, meaning roughly 4 million BTC—about 25% of the total—are at risk. At current prices, these coins are worth over $40 billion.

This represents approximately one-quarter of all Bitcoin in circulation. If quantum computer attacks succeed, the impact on the crypto market would be enormous. Moving assets away from vulnerable addresses and adopting quantum-resistant formats will be critical challenges ahead.

Can Current Quantum Computing Technology Break Bitcoin?

Google recently introduced the "Willow" quantum computing chip, which completed a calculation that would take a conventional supercomputer ten septillion years in just five minutes. However, Willow is not yet capable of breaking Bitcoin's encryption.

Current quantum computers—including Willow—suffer from high error rates and scalability limits. To break Bitcoin's cryptography, millions of error-corrected "logical qubits" are required, but Willow has only 105 "physical qubits." About 5,000 logical qubits (equivalent to millions of physical qubits) are needed to decode Bitcoin's cryptographic algorithms. With only 105 physical qubits, Willow is still at a very early stage.

According to Deloitte, quantum computers at today's technical level would take 30 minutes to break Bitcoin signatures, so avoiding address reuse keeps assets safe. If computation time drops below 10 minutes in the future, the Bitcoin blockchain could become vulnerable.

Fujitsu's research team found that breaking 2,048-bit RSA encryption would require about 10,000 logical qubits, over 2 trillion operations, and 104 days of stable operation—well beyond current technology. Based on this, breaking Bitcoin's SHA-256 would require 1 million qubits, and a 51% attack would need 1 billion qubits, levels that are 1,000 to 1 million times beyond current quantum computers. These figures indicate that the likelihood of quantum computers breaking Bitcoin soon is extremely low.

Ethereum Is Already Preparing for Quantum Computing

Meanwhile, blockchain projects like Ethereum are preparing for quantum computing. Ethereum co-founder Vitalik Buterin recently announced the next phase, "Surge."

The primary focus of "Surge" is to address quantum computer threats. Buterin emphasized the need for Ethereum to be resilient against technologies that could break current encryption standards. He explained that "Surge" tackles "small challenges" critical to Ethereum's success, though not part of larger categories. While practical quantum computers don't exist yet, Buterin stressed that investing in advanced cryptographic technology is essential for long-term blockchain security.

Ethereum's efforts mark an important step in raising industry-wide awareness of quantum resistance and are influencing other blockchain projects.

Bitcoin PoW Developers Reject Near-Term Bitcoin Collapse

Ki Young Ju, CEO of the on-chain analytics platform CryptoQuant, dismissed concerns on X about quantum computers threatening Bitcoin's security:

Bitcoin will not be broken by quantum computers for decades to come. Don't fall for baseless FUD (fear, uncertainty, doubt) spread by uninformed sources. Incidentally, Adam Back is a legendary cryptographer and the inventor of Bitcoin's Proof-of-Work (PoW) algorithm.

Adam Back, cryptographer and developer of Bitcoin's Proof-of-Work algorithm, has expressed similar views. He notes that current quantum technology is insufficient to break Bitcoin's encryption, and increasing qubit counts doesn't directly improve quantum entanglement performance. He predicts that several orders of magnitude breakthroughs are needed to threaten Bitcoin, and it could take around 50 years to achieve.

These expert opinions indicate that today's quantum computing technology poses no immediate threat to Bitcoin, but highlight the importance of long-term defense planning.

Summary: The Path Forward for Quantum Computing

The evolution of quantum computers presents new challenges for crypto assets, especially Bitcoin. While Satoshi Nakamoto's early wallets and some old P2PK address formats are seen as potential targets, many hurdles remain for current quantum technology. Meanwhile, efforts to develop quantum-resistant cryptography and anticipate quantum threats are underway across the industry.

As shown by Google's "Willow" and Fujitsu's research, quantum computers today would require leaps in capability to break Bitcoin's encryption. Current estimates suggest 1 million to 1 billion qubits are needed—1,000 to 1 million times more than today's technology.

However, technological progress can outpace predictions. As Ethereum begins quantum resistance initiatives with "Surge," the Bitcoin community must also consider long-term strategies. Developing quantum-resistant cryptography, migrating assets from legacy address formats, and updating protocols as needed require a multi-layered approach.

Flexible adaptation to future technological advances and ongoing investment in R&D will be key to maintaining Bitcoin's security. The broader crypto community must collaborate to establish new security standards for the quantum era, which remains a critical challenge going forward.

FAQ

How Can Quantum Computers Break Bitcoin's Encryption?

Quantum computers use Shor's algorithm to exploit vulnerabilities in Bitcoin's ECDSA encryption. They could theoretically reverse private keys from public keys, making the threat real as early as the 2030s. Migration to quantum-resistant cryptography is underway.

How Long Until Quantum Computers Threaten Bitcoin?

Experts predict that quantum computers could pose a substantial threat to Bitcoin's security in 2–3 years. "Q-Day" (quantum supremacy) is approaching, and industry-wide preparations are accelerating.

How Is Bitcoin Defending Against Quantum Attacks?

Bitcoin does not currently have quantum-resistant technology. However, vulnerabilities in elliptic curve signatures are recognized, and future upgrades to signature schemes or migration to post-quantum cryptography are being considered. Measures are expected to be implemented before quantum threats become reality.

What Is Quantum-Resistant (Post-Quantum) Cryptography, and Can It Be Used with Bitcoin?

Quantum-resistant cryptography is designed to withstand quantum computer threats. It can be applied to Bitcoin, and post-quantum algorithms like ML-DSA were standardized in August 2024. Proper implementation can strengthen Bitcoin's security.

Can Current Bitcoin Wallets and Private Keys Be Broken by Quantum Computers?

Currently, quantum computers cannot break Bitcoin private keys. However, if quantum computers become sufficiently advanced, it could be theoretically possible. As of 2026, practical quantum computers do not exist, so there is no immediate concern.

Is There a Plan to Upgrade the Bitcoin Network for Quantum Threats?

The Bitcoin network has not announced specific upgrade plans for quantum threats. However, Bitcoin's architecture is highly adaptable, and experts believe there is enough time before quantum computers become an actual risk. They predict the threat won't materialize for 10–20 years, allowing for adequate technical responses by then.

How Does Bitcoin Compare to Other Blockchains in Quantum Vulnerability?

Bitcoin relies on ECDSA encryption and is most vulnerable to quantum computer attacks. SHA-256 offers greater resistance. Compared to other blockchains, Bitcoin is slower to implement quantum threat countermeasures, with a crisis expected in the 2030s.