Researchers at quantum computing firm Alice & Bob estimate that a machine with about 30,000 physical qubits could break the cryptography protecting bitcoin wallets in roughly 62 minutes. The findings are theoretical, but they add pressure on Bitcoin developers to start moving to quantum-resistant security.
Alice & Bob researchers estimate that a machine with about 30,000 physical qubits could break the cryptography protecting bitcoin wallets in just over an hour. That is far less hardware than earlier models suggested.
A 17-fold cut from Google's estimate
Google estimated in March that a future quantum computer would need fewer than 500,000 physical qubits, down from previous estimates in the millions. Alice & Bob's new figure of 29,588 qubits is roughly 17 times lower, although the two studies use different hardware designs and assumptions.
The findings suggest the computing power needed to threaten Bitcoin could be smaller than previously expected. They could also bring such attacks closer to reality than previously believed.
Exposed keys are the main target
The attack would take roughly 62 minutes, compared with Bitcoin's average block time of 10 minutes. It is therefore too slow to reliably steal funds from a transaction before confirmation.
Coins at addresses with an exposed public key face a different risk, because an attacker would have more time to derive the private key. More than 6 million bitcoins sit behind exposed public keys, making them potential targets for future quantum attacks.
Researchers urge migration now
Dahmun Goudarzi, senior cryptanalyst at Alice & Bob, told CoinDesk that migration needs to start now. He stressed that the findings are theoretical, and said his company expects hardware improvements and declining resource requirements to converge in the early 2030s.
Asked whether more qubits could cut the attack time below 10 minutes, Goudarzi said his team had not yet completed the necessary calculations. On the limits of the approach, he said, according to CoinDesk: "There is no architectural floor,"
Replacing vulnerable signatures across a decentralized network could take years, even while the machines able to exploit them are still being developed.
Source: CoinDesk
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