Quantum Computing Threatens Bitcoin Security: Timeline Accelerated

Recent research from Google Quantum AI, co-authored with Ethereum Foundation and Stanford researchers, significantly reduces the estimated timeline and hardware requirements for quantum computers to break the cryptography securing Bitcoin and other cryptocurrencies. Previous estimates required millions of qubits, but Google’s findings suggest a sufficiently advanced quantum system could achieve this with fewer than 500,000 physical qubits – a 20-fold reduction. This accelerates the potential “Q-Day” scenario, with some estimates now placing it within the next decade. A key vulnerability lies in ‘on-spend’ attacks, where a private key could be cracked in under nine minutes, potentially allowing attackers to intercept and redirect transactions. Approximately $450 billion in Bitcoin is held in vulnerable wallets, particularly older ones with exposed public keys. The research highlights three attack vectors: targeting transactions in flight, dormant wallets, and protocol weaknesses. Experts urge a swift migration to post-quantum cryptography (PQC) to mitigate these risks, though implementation at scale presents challenges. The Taproot upgrade may have inadvertently increased vulnerability by exposing more public keys.