The quantum computing buzz has quieted somewhat, but back in December 2024, it sparked significant interest within the market. Google’s excitement around its quantum chip, Willow, prompted widespread debate over potential implications for Bitcoin. Understandably, concerns emerged given claims that Willow could complete tasks in five minutes that would take some of the world’s fastest conventional computers 10 septillion years to solve.
Let’s explore whether these concerns are justified.
What is quantum computing?
Quantum computing leverages quantum mechanics—the fundamental principles governing particles at the smallest scales (like atoms and photons)—to process information in ways that traditional computers cannot.
Unlike classical computers, which use bits (0s or 1s) to transmit data, quantum computers use qubits, which can exist as 0, 1, or both simultaneously (a property known as superposition). This enables quantum computers to process many calculations concurrently. Moreover, while adding more bits to a classical computer increases its power linearly, adding qubits to a quantum computer increases its power exponentially.
Potential Threats to Bitcoin
The primary concern revolves around Shor’s algorithm, which, theoretically, a sufficiently powerful quantum computer could use to break modern cryptographic systems, including Bitcoin’s Elliptic Curve Digital Signature Algorithm (ECDSA).
In essence, a powerful quantum computer could potentially deduce private keys from public keys, presenting a critical security risk for Bitcoin wallets. However, Bitcoin addresses are generally protected because the public key is only revealed after a transaction is made. Reusing addresses increases vulnerability, but avoiding reuse enhances security.
Additionally, mining security, protected by the SHA-256 algorithm, would be significantly harder to compromise using Grover’s algorithm.
We could go into detail and talk about the specific risks that relate to specific types of wallets, but we’d be getting lost in the weeds. What we want to know is, is there significant risk here?
Assessing the Actual Threat
With current hardware:
· As mentioned above, Willow is powerful for current quantum tasks and has performed a computation in under five minutes that would take a supercomputer 10 septillion years, demonstrating its potential for solving complex problems beyond the reach of classical computers, but cracking Bitcoin’s cryptography is a long way off. We’re probably 10-20 years from developing a quantum computer capable of such a feat, assuming steady progress.
In the future, with error-corrected quantum computers:
· Estimates suggest breaking ECDSA within an hour would require approximately 317 million physical qubits. Even if the timeline were extended to five years, it would still take around 6,000 qubits to crack ECDSA. To put this in perspective, even the best quantum computers today are in the low 100’s of qubits range (and they’re noisy, which means they are prone to errors).
Other estimates suggest 10 million to 100 million physical qubits would be needed to break Bitcoin’s ECDSA effectively, highlighting a lack of consensus on the required power. Without precise power requirements, accurately predicting the timeline for a practical quantum threat remains challenging.
The image below shows Mara’s estimates on Qubit growth:
Mitigations
While quantum computing could eventually pose a risk to Bitcoin, it is not an immediate threat. Bitcoin’s security primarily relies on cryptographic algorithms like SHA-256 (used in mining) and ECDSA (used in wallet keys).
- Quantum-Resistant Algorithms: Researchers are actively exploring post-quantum cryptography. Bitcoin could adopt quantum-resistant algorithms (e.g., XMSS or lattice-based cryptography) through a soft or hard fork.
- Avoiding Address Reuse: Best practice to only use a Bitcoin address once and generate a new address for each transaction to enhances security. To check if your address has been reused, you can paste your address into a block explorer to see if has been used in any transactions in the past.
- Timeline Considerations: Practical quantum computers capable of breaking Bitcoin’s cryptography are likely decades away.
Post Quantum Upgrade Issues
Most Bitcoin holdings will be protected post-upgrade, but some may remain vulnerable. Primarily this impacts ‘’lost’’ Bitcoin and estimates suggest that between 3 million to 4 million BTC have been lost permanently. This is about 14% to 19% of the total supply of 21 million BTC. These coins may never migrate to safer addresses, raising questions about their potential exposure to theft via quantum attacks. Proposals to disable or move these coins to protect them would require a soft fork of the Bitcoin protocol. However, this approach is fraught with challenges:
- It risks being perceived as confiscatory, as proving coins are truly lost is nearly impossible.
- It contradicts Bitcoin’s foundational philosophy of “not your keys, not your coins.”
It is likely that lost coins will remain dormant until quantum computers become powerful enough to forge their private keys—a scenario that may never materialize. If it does, how these coins are treated from legal and regulatory perspectives will be uncertain.
It’s also likely that this technology will pose a greater risk to more traditional technologies such as our banking systems, Secure communications, Internet encryption, Energy Infrastructure and an endless list of technologies that we rely on every day to keep us safe and connected. Bitcoin is uniquely positioned to respond much faster to the quantum threat than any of those systems, making it a harder target and making Bitcoin a safer place for our pennies in the future. As quantum threats grow, blockchain technology could become the standard for securing critical systems.
Conclusion
For now, quantum computers are decades away from posing a serious threat to Bitcoin. The gap between today’s quantum computers (measured in hundreds of qubits) and the millions required to break Bitcoin’s cryptography is vast. Even with rapid progress, most experts agree that a practical threat is unlikely before 2035, and possibly much later. In the meantime, the Bitcoin community is actively exploring quantum-resistant solutions, suggesting that by the time quantum computers pose a legitimate risk, Bitcoin may have already adapted.
Moreover, the potential benefits of quantum computing are profound and exciting, far beyond the scope of cryptocurrency security. Quantum computers could revolutionize fields such as drug discovery, genomics, optimization, artificial intelligence, and machine learning.
Just a reminder this is my opinion not financial advice, please make sure to do your own research.
