Home › Videos › Episode 2: quantum myth

Episode 2: will quantum computers break Bitcoin?

Myth vs Data with Blocky. The written guide to our second episode: what a quantum computer could and could not reach, the real numbers, and the one habit you control.

The myth

"Quantum computers will crack Bitcoin and send it to zero." Blocky checks that claim against the data.

The lesson, step by step

Step 1: Know what a quantum computer could actually attack

The worry is that a large enough quantum computer running a method called Shor's algorithm could work out a private key from a public key. No machine that can do this exists today. Mining uses a different kind of maths (SHA-256), and that is not the main risk.

Step 2: Understand when your public key is visible

Most modern addresses hide the public key behind a hash. It only appears on the blockchain when you spend from that address. Coins are exposed when the public key is already out in the open: very old pay-to-public-key outputs, Taproot key-path outputs, and any address that has been spent from and then reused.

Step 3: Look at the numbers

Glassnode found about 6.04 million BTC sitting behind public keys that are already visible. About 4.12 million of that comes from address reuse and custody habits, and it shrinks as coins move to fresh addresses. Other researchers count reuse differently and land between about 6.3 and 6.9 million. Either way, most bitcoin is not in that group. The full breakdown is in Bitcoin myths vs data.

Step 4: See what developers are discussing

Proposals such as BIP-360 (a Taproot-style output without the exposed key path) and BIP-361 (a phased move away from vulnerable address types) are drafts. Neither has agreement yet. Any change would go through the same slow process as every other Bitcoin rule.

Step 5: Separate the risk from the headline

The myth gets one thing right: exposed public keys are a real long-term risk and the network will need a plan. It gets the scale wrong. A future attack would target exposed coins, not every coin, and you can keep yours out of that group today.

What to do today

1. Use a new receive address every time. Most wallets do this for you. Our guide: Use a new receive address every time.
2. Do not post one address publicly for lots of payments.
3. Know what type of address your wallet uses. See How Bitcoin addresses work.
4. If your coins sit on an exchange, its address habits are out of your hands. Holding your own keys fixes that. See How to move bitcoin from an exchange to your own wallet.
5. Follow the actual proposals, not panicky headlines. A scary headline is not a reason to sell.

Key takeaways

• No quantum computer today can break Bitcoin keys.
• Only coins with a visible public key would be at risk, and most bitcoin is not in that group.
• Address reuse is the biggest habit that adds to the exposed pile.
• A new receive address every time is the simple fix you control.

Episode 1: 21 million Self-custody check More myths vs data

FAQ

Not financial advice. General education only. Bitcoin prices can swing hard. Never put in more than you can afford to lose, and do your own research. We will never ask for your recovery words or keys.