- Quantum computers are not considered an immediate threat to Bitcoin, but experts say preparation should begin now.
- About 6.7 million BTC may be exposed because their public keys are already visible or their addresses were reused.
- The hardest question is whether old, unmoved coins should remain spendable once Bitcoin adopts stronger security.
A group of leading cryptographers is urging the Bitcoin community to begin planning for a future upgrade that can resist attacks from quantum computers.
The recommendation comes from a Coinbase advisory council whose members include researchers from Stanford University, the University of Texas at Austin, and the Ethereum Foundation. According to a CoinDesk report published on June 13, the council does not believe quantum computers can break Bitcoin today. However, it says the engineering work should start before the threat becomes urgent.
Quantum computers use a different type of computing that could eventually solve some mathematical problems much faster than current machines. If they become powerful enough, they may be able to calculate a private key from a visible public key. A private key is the secret code that allows someone to spend bitcoin from a wallet.
The concern is larger for older Bitcoin addresses. Around 1.7 million BTC are held in early addresses that display their public keys directly on the blockchain. Some of these coins are believed to belong to Bitcoin creator Satoshi Nakamoto, while others may be locked in wallets whose owners lost their keys.
Researchers also estimate that roughly 5 million more BTC could be exposed because people reused addresses. Many of those coins may still be controlled by active users or exchanges, which means they could potentially move to safer addresses when new security tools become available.
Adding quantum-resistant digital signatures is only part of the challenge. Bitcoin developers and users must also decide what happens to coins that never move.
One option would set a deadline. After that date, coins using older signature methods could no longer be spent unless their owners had migrated them. Supporters say this could stop a future attacker from stealing a large amount of dormant bitcoin and selling it into the market.
Critics argue that such a rule would effectively freeze property and conflict with Bitcoin principles. They also worry that it could create a precedent for blocking coins for other reasons.
Several proposals try to balance these concerns. Some would limit how many vulnerable coins could move in each block. Others would let owners prove control through a quantum-resistant method or register a private claim before any deadline.
The advisory council did not support one specific proposal. Instead, it said several ideas may work together. Its main message is that technical preparation and clear communication should begin now, even if the community has not settled the debate over old or abandoned coins.
Source: CoinDesk, “What happens to Satoshi’s BTC when Bitcoin’s quantum problem is fixed?”, published June 13, 2026.
