New Quantum Model Cuts Estimated Hardware Needed to Break Bitcoin Keys by 17 Times

Quantum Attack on Bitcoin Could Need Far Less Hardware Than Expected

Researchers at quantum computing firm Alice & Bob have published a new theoretical model showing that breaking the cryptography protecting bitcoin wallets could require far less quantum computing hardware than previously estimated. Quantum computers use the principles of quantum physics to solve certain types of problems much faster than regular computers.

The findings suggest the computing power needed to threaten Bitcoin, a digital cryptocurrency that uses cryptography to secure transactions, could be smaller than previously expected.

Key Research Findings

• Researchers estimate a quantum computer with about 29,588 physical qubits — the basic processing units of quantum computers — could crack Bitcoin's cryptography in roughly 62 minutes


• The estimate is about 17 times lower than Google's earlier figure of fewer than 500,000 qubits


• More than six million bitcoins are held at addresses with exposed public keys, putting them at potential risk


• The 62-minute attack time is too slow to reliably steal funds from a transaction before it is confirmed


• The findings remain theoretical

How the New Model Compares to Previous Estimates

Google estimated in March 2026 that a future quantum computer would need fewer than 500,000 physical qubits to crack Bitcoin's cryptography. Before that, estimates were in the millions.

Alice & Bob's new estimate of 29,588 qubits is roughly 17 times lower than Google's March figure. The two studies use different hardware designs and assumptions, so direct comparison has limits.

Millions of Bitcoin at Risk From Exposed Public Keys

The research raises particular concerns about bitcoin held at addresses whose public keys are already exposed. A public key is a cryptographic code that allows the Bitcoin network to verify transactions without revealing the private key — the secret code used to authorize spending.

A powerful quantum computer could potentially work backwards from a public key to recover the corresponding private key and steal the coins. More than six million bitcoins sit at addresses with exposed public keys, giving attackers more time to target them.

The attack would take roughly 62 minutes, compared with Bitcoin's average block time of 10 minutes. Block time is how long it takes the Bitcoin network to process a new set of transactions. This makes the attack too slow to reliably intercept and steal funds from a transaction before it is confirmed.

Researchers Call for Early Quantum-Resistant Upgrades

The researchers urge Bitcoin developers to begin moving to quantum-resistant security now. They warn that upgrades could take years, while potentially threatening hardware advances toward the early 2030s.

"Yes, it becomes of utmost importance that migration starts now," Dahmun Goudarzi, senior cryptanalyst at Alice & Bob, told CoinDesk. "We know how hard and long this task can be, and this paper shows that Shor's algorithm could be run sooner than later."

Goudarzi, who holds a PhD in cryptography, said there is "no architectural floor" — meaning further work could produce even lower hardware estimates than the current model.

What Remains Uncertain

All of the findings remain theoretical — no quantum computer with enough qubits to carry out this attack currently exists.

It is not yet clear whether adding more qubits could cut the attack time below Bitcoin's 10-minute block window. Goudarzi said his team had not yet completed the necessary calculations to answer that question.

The different hardware designs and assumptions used by Alice & Bob and Google also make direct comparison between the two estimates difficult.

Why This Matters for Bitcoin Users

If quantum computing hardware advances as the researchers suggest, Bitcoin may need significant security upgrades to remain protected. The researchers warn that preparing those upgrades could take years, which is why they are calling for action now rather than waiting for the threat to become immediate.

More than six million bitcoins could be vulnerable to a future quantum attack if their public keys remain exposed and security is not upgraded in time.

Sources

• CoinDesk