On March 30, 2026, Google Quantum AI published a <\/span>new whitepaper<\/span><\/a> revealing that a theoretical quantum computer could derive a private key from a public key on the Bitcoin<\/a> network in just a few minutes. This timeframe closely aligns with Bitcoin\u2019s 10-minute mining cycle, raising the scenario of an \u201cOn-Spend Attack\u201d where a transaction pending confirmation could be intercepted and replaced.<\/span><\/p>\n Additionally, Google experts recommended that blockchain projects complete their migration to Post-Quantum Cryptography (PQC) before 2029 to safeguard digital signatures and transactions against sufficiently powerful future quantum computers.<\/span><\/p>\n The research illustrates a scenario in which quantum computers could compromise the core security mechanisms of Bitcoin and Ethereum. Instead of a direct attack on the wallet, this method targets the public key\u2014which becomes visible on the blockchain during a transaction\u2014to derive the private key, the ultimate factor controlling the assets.<\/span><\/p>\n Current security relies on cryptographic problems considered nearly impossible for classical computers to solve, but which could be significantly accelerated by quantum systems. According to Google\u2019s estimates, a theoretical quantum system could perform this calculation using approximately <\/span>1,200\u20131,450 logical qubits<\/b> and <\/span>70\u201390 million Toffoli<\/b> gates, with a total physical qubit count under <\/span>500,000 physical<\/b>\u2014substantially lower than previous projections. These estimates were validated using the Zero-Knowledge Proof (ZKP) method.<\/span><\/p>\n In architectures utilizing superconducting systems, execution time could be reduced to mere minutes. This is particularly critical because public keys are typically exposed only during the transaction process, creating a narrow window of vulnerability where assets could be exploited if the private key is derived rapidly enough.<\/span><\/p>\n However, the research emphasizes that quantum computers with sufficient power to execute this scenario do not yet exist, and current estimates reflect capabilities under theoretical conditions.<\/span><\/p>\n A primary scenario highlighted in the report is the \u201c<\/span>On-Spend Attack<\/b>,\u201d targeting transactions pending in the network\u2019s mempool. Once a public key is broadcast after a transaction is initiated, a theoretical quantum system could attempt to derive the private key before the next block is confirmed.<\/span><\/p>\n With the Bitcoin network\u2019s average confirmation time of 10 minutes, a \u201cwaiting window\u201d is created, allowing an attacker to compete directly with the original transaction. If the calculation is completed in time, they could broadcast a replacement transaction with a higher fee to ensure priority inclusion in the block.<\/span><\/p>\nUnderstanding the Quantum Threat<\/b>\u00a0<\/span><\/h2>\n
Inside Bitcoin\u2019s 10-Minute Window<\/b>\u00a0<\/span><\/h2>\n
![\"Race](\"https:\/\/nftevening.com\/wp-content\/uploads\/2026\/04\/Race-Against-the-Block-Attack-Speed-vs.-Network-Variance.png\")