Quantum computers could, in theory, compute a private key from a public key, reviving Bitcoin long considered lost and threatening both supply and trust. The main exposure lies in old wallets whose public keys are already revealed, making dormant balances vulnerable if large-scale quantum capability emerges. While no such machine exists today, timelines range from decades to as early as 2027–2030, raising urgency across developers, exchanges, and institutions.
A sufficiently powerful quantum computer running Shor’s algorithm could derive private keys from exposed public keys, enabling attackers to unlock idle balances, move dormant coins, and potentially alter Bitcoin’s supply dynamics and market trust.
No practical quantum computer exists today at the required scale; sources she cites estimate the need at roughly 13 to 300 million qubits. Most assessments push practical deployment several decades out, though some forecasts narrow the window to 2027–2030, keeping the community alert to the risk.
Addresses that have already revealed a public key sit on the front line, as their linked private keys could be computed first. Any recovery and spending of such dormant coins could add millions of BTC to the liquid supply, with meaningful price and confidence implications.
Responses, migration paths, and plausible outcomes
Post-Quantum Cryptography (PQC) aims to resist both classical and quantum attacks, and that developers, exchanges, and states are already responding. NIST and the community are advancing schemes such as CRYSTALS-Kyber, CRYSTALS-Dilithium, and SPHINCS+, while BIP drafts outline migration paths and some users move to “freeze” weak addresses.
Recent actions underscore the shift: El Salvador moved 6,274 BTC into fourteen new addresses, each holding 500 BTC or less, and BlackRock amended its ETF prospectus to flag quantum risk.
The next checkpoint will be the discussion of BIP drafts and a roadmap targeting migration around 2030, a debate that will reveal how ready the network and its custodians are.
Bitcoin’s resilience hinges on the community’s progress toward post-quantum migration. As debate advances toward a 2030 target, the balance between advancing hardware and resistant code will determine whether Bitcoin remains safe and usable.
