Hayes: Quantum Computing Not Bitcoin’s Real Threat

Hayes points to address reuse as the primary quantum risk: receiving and spending coins again and again from the same address. Quantum computers remain a theoretical threat, but the habit creates an exposure point today, and many anxious investors are already weighing a sale over quantum headlines.

How Reuse Exposes Your Public Key

Every Bitcoin address is tied to a key pair: a private key for spending and a public key for verifying transactions. A standard computer cannot work backward from a public key to the private key. A sufficiently powerful quantum computer theoretically could. Most modern addresses initially show only a hashed version of the public key.

The full public key becomes visible on the blockchain with the first transaction sent from that address. If the address is never used again, nothing is at risk. But any new coins received there afterward sit behind a public key that is already exposed, which makes them a potential target for a future quantum attack. Older address formats and Taproot addresses, introduced in 2021, reveal the public key from the start.

The fix for everyday users is simple:

• Use a fresh receiving address for every transaction. Most modern wallets generate new addresses automatically from the same backup seed phrase, and the Bitcoin Wiki advises against reusing an address once coins have been spent from it.
• If you have already reused an address, move the balance to a new address in the same wallet to hide the public key again.
• When withdrawing from an exchange, send each withdrawal to a newly generated address.
• Keep long-term savings in an address that has received coins but never spent them.

The Part Users Cannot Fix

Quantum computers cannot break Bitcoin’s cryptography today. Coinbase has suggested that preparing Bitcoin for post-quantum cryptography could take years, which gives individual holders time to clean up their wallet habits. The market has not flinched either: Bitcoin rose 26.1% in the 60 days leading up to mid-October despite the quantum warnings.

The harder problem belongs to developers. Coins whose keys are already exposed, particularly older, unspent ones, would need a network-wide update. That requires consensus from developers, miners, and node operators, a process that could take considerable time. Coinbase research found about 20,000 addresses holding at least 50 BTC each with exposed keys, totaling roughly 6.9 million BTC.

Hashlytics Take

Hayes is right that address reuse is the part of the quantum story an individual can actually act on, and the checklist above costs nothing. But it only covers new money. The 6.9 million BTC already sitting behind exposed keys cannot be fixed by good habits, because many of those coins belong to holders who may never move them and cannot be forced to. That leaves the risk with the protocol, where change needs agreement from people who rarely agree quickly. The more useful question for holders is not whether quantum arrives this year, but whether Bitcoin’s governance can finish a migration before it has to.