Study Revises Qubit Estimate for Cracking a Bitcoin Key

Breaking a Bitcoin network key using Shor’s algorithm requires significantly fewer quantum computing resources than previously thought, according to researchers at Alice & Bob, a company specializing in quantum computing. The authors of the study clarified that Shor’s algorithm is capable of breaking robust encryption systems.

Cracking the widely used RSA-2048 scheme would take less than 23 000 physical qubits operating for just three days, according to the researchers’ results. To crack a Bitcoin blockchain key, 29 588 physical qubits would be needed—approximately 17 times lower than the previous estimate provided by Google (around 500 000 qubits). At these parameters, cracking a single key could take just 62 minutes. A qubit is the basic unit of information in quantum computing: the more qubits, the more powerful the computer.

The figures cited assume no bit-flip errors occur during computation. If such errors occur roughly once an hour, cracking RSA-2048 would require about 45 000 qubits, Alice & Bob specialists clarified. Nevertheless, the speed of 62 minutes still would not allow a reliable attack on unconfirmed transactions, the researchers insist: the average block formation time in the Bitcoin network is ten minutes, which creates additional difficulties for attackers.

According to Alice & Bob’s forecast, the technical possibility of conducting a quantum attack will arise in the early 2030s. More than 6 million BTC will be at risk then—these funds are stored at addresses where public keys have already been exposed.

Previously, Ethereum co-founder Vitalik Buterin suggested that quantum computers might gain the ability to crack the cryptographic protection of Bitcoin and other blockchains as early as 2028. In his view, developers need to prepare the networks in advance for the emergence of such a threat.