Google: “Bitcoin could be cracked by quantum computers sooner than expected”

An analysis has warned that Bitcoin’s (BTC) security may be exposed to quantum-computing threats sooner than expected.

According to CoinDesk on the 31st (local time), Google’s Quantum Artificial Intelligence (AI) team said in a blog post and a white paper that “the quantum-computing capability required to break the cryptographic systems of Bitcoin and Ethereum (ETH) could be lower than previously estimated,” and cautioned that they “could be compromised by quantum-computing attacks earlier than anticipated.”

The researchers estimate the attack would require fewer than about 500,000 physical qubits. That is far below the “millions” previously cited. In particular, two attack scenarios suggested feasibility with only about 1,200–1,450 high-performance qubits.

Quantum computers can perform certain calculations far faster than conventional computers and have the potential to decrypt the cryptography that protects virtual-asset (cryptocurrency) wallets.

The study also proposed a concrete attack method: deriving the private key from the public key revealed when a transaction occurs and stealing funds. Under this model, an attack could be carried out in about nine minutes, and given Bitcoin’s transaction confirmation time (about 10 minutes), the probability of a successful attack was estimated at about 41%.

The scale of assets already exposed also appears substantial. Bitcoins with exposed public keys total about 6.9 million, roughly one-third of total supply—well above some earlier estimates.

The study also raised the possibility that the Taproot upgrade introduced in 2021 may have amplified this vulnerability. While Taproot improved transaction efficiency and privacy, it adopted a structure in which public keys are by default exposed on the blockchain, potentially weakening some safeguards.

The researchers stressed that “quantum computers have not yet reached a level that immediately threatens Bitcoin’s security,” but added that “given the pace of technological progress, the risk horizon could arrive sooner than expected, increasing the need for preparedness.”