Bitcoin’s No.1 Long-Term Threat: Quantum Computing, Clock Is Ticking

Key Insights

• Quantum risk is now a planning issue, not just theory. Breakthroughs haven’t broken Bitcoin yet, but they’ve made preparation unavoidable.
• About 25% of Bitcoin may be exposed. Roughly 6.5 million BTC sit in addresses vulnerable to future quantum attacks.
• Dormant coins are the biggest wildcard. Quantum access to long-inactive wallets could trigger massive wealth redistribution.

As quantum breakthroughs accelerate, Bitcoin developers and cryptographers are racing to secure the network before today’s unbreakable math becomes tomorrow’s weak link.

Quantum computing, once the domain of science fiction, is now one of Bitcoin’s most uncomfortable realities.

It’s not an existential threat — yet. But the pace of quantum research has moved fast enough that what was once dismissed as a distant, theoretical risk is now forcing serious conversations among cryptographers, protocol developers, institutional investors, and regulators.

The question haunting Bitcoin’s inner circles is no longer if quantum computing could threaten the network — but whether Bitcoin is moving fast enough to stay ahead of it.

As Bitcoin advocate and Coin Metrics co-founder Nic Carter has put it bluntly:

The Cryptographic Assumption Bitcoin Lives By

Bitcoin’s security rests on a simple but powerful assumption: certain mathematical problems are easy to compute in one direction and practically impossible to reverse.

Today, Bitcoin relies on elliptic curve cryptography (ECC) to generate public-private key pairs. You can share your public key freely, but deriving the private key from it would take a classical computer longer than the age of the universe.

That assumption breaks down in the presence of a sufficiently powerful quantum computer.

Quantum algorithms — particularly Shor’s algorithm — are designed to dismantle the math underlying ECC. In theory, a quantum machine with enough stable, error-corrected qubits could extract private keys from exposed public keys in hours or days, not millennia.

Another quantum tool, Grover’s algorithm, weakens hash functions like SHA-256 by effectively halving their security margin. While not an outright break, it further compresses Bitcoin’s defensive buffer.

Put simply: quantum computing doesn’t just make Bitcoin’s cryptography slightly weaker — it changes the rules of the game entirely.

How Much Bitcoin Is Actually at Risk?

Not all Bitcoin is equally exposed.

Most modern Bitcoin addresses keep their public keys hidden until coins are spent. But older address types — and any address that has already been spent from — have public keys permanently visible on the blockchain.

Estimates suggest roughly 6.5 to 6.7 million BTC, or about 25% of the total supply, fall into categories vulnerable to long-range quantum attacks. At late-2025 prices, that represents hundreds of billions of dollars in potential exposure.

This opens the door to a troubling strategy known as “harvest now, decrypt later.”
An attacker doesn’t need quantum hardware today. They only need to collect exposed public keys and wait.

When quantum machines eventually cross the cryptographic threshold, those keys become targets.

The Dormant Coin Problem

The most unsettling implication involves Bitcoin’s dormant wallets.

Coins that haven’t moved in a decade — including those attributed to Satoshi Nakamoto — have long been viewed as lost, untouchable, or economically irrelevant. But quantum computing challenges that assumption.

Jameson Lopp, Casa co-founder and longtime Bitcoin core contributor, has warned that allowing quantum recovery of old coins would amount to large-scale wealth redistribution:

The governance dilemma is stark.
Should the network intervene to freeze or invalidate vulnerable coins? Or should it preserve Bitcoin’s original rules — even if that leads to unprecedented theft?

Neither option aligns comfortably with Bitcoin’s ethos.

Why Bitcoin Can’t Simply ‘Upgrade’ Overnight

On paper, the solution seems obvious: migrate Bitcoin to post-quantum cryptography.

In practice, it’s anything but simple.

Quantum-resistant signature schemes — such as lattice-based or hash-based cryptography — tend to produce much larger signatures and addresses. That means higher transaction fees, more blockchain bloat, and potentially reduced accessibility.

Even more challenging is the social layer.

A full migration would likely require a hard fork, forcing the decentralized Bitcoin ecosystem to agree on sweeping changes to its most sacred assumptions. History suggests that such consensus is slow, contentious, and anything but guaranteed.

As Lopp has noted, if quantum computing truly breaks ECC, some inviolable property of Bitcoin will be violated — no matter what path is chosen.

Urgency vs. Skepticism

Views on the timeline diverge sharply.

Adam Back, Blockstream CEO and one of Bitcoin’s most respected cryptographers, believes a cryptographically relevant quantum computer is still decades away — leaving ample time for a careful, orderly transition.

Others are less comfortable.

Ethereum co-founder Vitalik Buterin has suggested there may be a meaningful probability of ECC-breaking quantum machines emerging by the early 2030s.

Solana co-founder Anatoly Yakovenko has publicly warned that a breakthrough could arrive sooner than many expect.

The disagreement isn’t about whether quantum computing threatens Bitcoin — only when.

Real-World Responses Are Already Underway

This is no longer a purely academic debate.

Researchers are actively testing quantum-resistant Bitcoin transaction formats. Some teams have already demonstrated Bitcoin-compatible systems using NIST-standardized post-quantum cryptography, proving that a quantum-safe Bitcoin is technically possible.

The remaining challenge is coordination, not capability.

Bitcoin must upgrade before the threat materializes — because once quantum attacks become practical, it will be too late to react.

What Bitcoin Holders Can Do Now

For individual users, the immediate steps are pragmatic rather than dramatic:

• Avoid reusing addresses, which exposes public keys unnecessarily
• Migrate older holdings to modern address formats
• Monitor developments in quantum-resistant wallets and protocol proposals

These measures don’t solve the problem — but they reduce exposure while the network grapples with long-term solutions.

What The Future Holds

Quantum computing hasn’t broken Bitcoin. But it has already broken the illusion that Bitcoin’s cryptography is untouchable.

The real risk isn’t an overnight collapse — it’s complacency.

Whether the decisive breakthrough arrives in five years or twenty, Bitcoin’s future security depends on preparation today.

The longer the network delays confronting quantum risk, the more disruptive — and politically explosive — the eventual reckoning will be.

The quantum era is coming.
The only remaining question is whether Bitcoin will be ready when it does.