Google-linked projections about quantum computing capacity have pushed Bitcoin security back into focus. The report says that if quantum hardware reaches the required scale, an attacker could derive a private key from a public key in nine minutes, while Bitcoin transactions typically take about ten minutes to be confirmed. That gap creates a theoretical window in which funds could be redirected before settlement is finalized on-chain.
Bitcoin authorizes transfers with a private key and lets the network verify them through the matching public key. According to the article, an attacker would first need extensive preparatory computation. Once a transaction exposes the public key in the mempool, the remaining quantum work could, in theory, be completed before the transaction is included in a block. If that happened, the attacker could recover the private key in time to interfere with the transfer.
Older wallet formats and address reuse face the sharpest exposure
The article points to older wallets and any wallet that reuses addresses as the most exposed group. Early Bitcoin addresses created in the so-called pay-to-public-key format leave public keys directly visible on the blockchain. The same is true for wallets that repeatedly use one address. In those cases, an attacker would not need to wait for a fresh transaction because the target public key is already available on-chain.
It also says some experts view Bitcoin’s Taproot upgrade as an added risk factor. Taproot changed address formats and, in the article’s framing, increased the number of wallets with public keys directly exposed on-chain. That expands the potential attack surface, with the pressure falling on signature security rather than the mining process.
The hardware gap keeps the threat theoretical for now
For now, the risk remains theoretical. The report states that today’s most powerful quantum computers have roughly 1,000 physical qubits, while experts estimate that about 500,000 qubits would be needed to feasibly break Bitcoin’s cryptography. That leaves a wide gap between current machines and the level required for a practical attack.
The article separately notes that Bitcoin mining relies on the SHA-256 hashing algorithm. Quantum computers are not expected to produce major gains against SHA-256 in mining, so block production itself is not presented as the main concern. The real pressure point is whether exposed public keys could eventually allow private keys to be recovered fast enough to break user-level security.
Post-quantum migration is becoming a protocol question
The piece argues that the long-term answer is a move toward post-quantum cryptography in blockchain systems. It says Ethereum has spent years preparing for that kind of transition, while Bitcoin has not yet seriously discussed or implemented quantum-resistant preparations. The unresolved issue is how the network would handle a future upgrade without compromising compatibility and trust.