As quantum computing edges closer to reality, the crypto world is facing a pivotal question: what happens to Bitcoin when quantum computers arrive? While the technology promises breakthroughs in fields like medicine and logistics, it also poses a direct challenge to the cryptographic foundations that secure Bitcoin and other digital assets.
Quantum Computing: A Looming Threat or Distant Concern?
Quantum computers, unlike classical machines, leverage the principles of quantum mechanics to solve certain problems exponentially faster. For Bitcoin, the main concern is the potential for quantum computers to break the cryptographic algorithms—specifically Elliptic Curve Cryptography (ECC)—that underpin wallet security and transaction signatures 3. If a sufficiently powerful quantum computer (often called a CRQC: Cryptographically Relevant Quantum Computer) emerges, it could theoretically derive private keys from public keys, opening the door to large-scale theft of funds.
Recent research and industry roadmaps suggest that quantum computers capable of threatening Bitcoin’s security could arrive within the next five to ten years 1 4 5. Some experts warn that, without urgent upgrades, Bitcoin could be vulnerable as soon as 2030, with the U.S. National Institute of Standards and Technology (NIST) recommending a full transition to post-quantum cryptography by 2035 1 5.
How Much Bitcoin Is at Risk?
The stakes are high. Analysis shows that around 6,51 million bitcoins—over 32% of the current supply—are potentially vulnerable to quantum attacks. This includes coins held in addresses that have reused public keys or use older, less secure script types. If quantum computers become practical, these funds could be at risk of theft, especially if their public keys are exposed on the blockchain.
What Parts of Bitcoin Are Most Vulnerable?
• Transaction Signatures: The most immediate risk is to Bitcoin’s digital signatures. If a quantum computer can derive a private key from a public key, it can spend those coins. Addresses that reveal their public keys (due to address reuse or certain script types) are especially at risk, as attackers would have unlimited time to crack them.
• Mining: Quantum computers could also impact mining by using algorithms like Grover’s to search for valid blocks faster. However, experts believe that building a quantum computer capable of outperforming today’s ASIC miners is a much bigger challenge and likely decades away 3.
How Is the Bitcoin Community Preparing?
The Bitcoin ecosystem is considering a two-pronged approach:
• Long-Term Migration: A full transition to quantum-resistant cryptography could take up to seven years, drawing on lessons from previous upgrades like SegWit and Taproot.
• Short-Term Contingency: In case of a sudden quantum breakthrough, emergency measures could be rolled out in about two years to protect the network.
In both cases, funds stored in hashed address types (like P2PKH or P2WPKH) and not reused are safer, but spending them securely in a post-quantum world will require new infrastructure.
Challenges of Going Quantum-Safe
Switching to quantum-resistant signatures isn’t straightforward. New algorithms like SPHINCS+ and FALCON are promising, but they come with trade-offs: larger key and signature sizes, slower verification, and limited support for advanced features used in applications like the Lightning Network. Integrating these into Bitcoin will require careful planning, consensus changes, and possibly soft forks.
A Philosophical Crossroads: Burn or Steal?
A unique dilemma looms: should Bitcoin make quantum-vulnerable funds unspendable (“burned”) to prevent theft, or allow them to be stolen by whoever gets quantum capabilities first? Burning would protect the network’s integrity but could be seen as violating property rights. Allowing theft could lead to massive wealth transfers and market chaos. The community will need to balance security, user rights, and the core principles of Bitcoin as it decides.
What’s Next for Bitcoin and Quantum Computing?
While quantum computers aren’t an immediate threat, the window for proactive action is open now. The Bitcoin community is urged to stop address reuse, monitor quantum advances, and prepare for a future where quantum security is the norm. The coming years will be crucial in ensuring that Bitcoin remains resilient in a post-quantum world.
