More than 6 million Bitcoin — roughly 30% of the total supply — are vulnerable to a future quantum computer attack, according to fresh data from analytics firm Glassnode. The exposure stems from coins whose public keys are already visible on-chain, a prerequisite for a quantum adversary to derive a private key. At current prices around $77,000, that’s over $465 billion worth of BTC sitting in a riskier state than most holders probably realize.
The two flavors of exposure
Glassnode splits the unsafe supply into two buckets. Structural exposure covers outputs like Pay-to-Public-Key (P2PK) addresses, which by design reveal the public key on the blockchain. That category has actually shrunk over time — down to 1.92 million BTC, or 9.6% of supply — as wallet standards shifted toward more secure address types.
The bigger problem is operational exposure: coins that become visible because of address reuse, partial spending, or custody behavior that broadcasts the public key. That pool now sits at 4.12 million BTC, or 20.6% of supply. And unlike the structural side, it’s been growing in recent years.
Why P2PK and address reuse matter
The mechanics are straightforward. To spend a Bitcoin output, the owner must reveal the public key in the transaction signature. Normally, that key is only exposed at the moment of spending. But P2PK addresses publish it from day one. And when users reuse a receiving address multiple times, the public key for every unspent output tied to that address eventually becomes visible the first time any of those coins move.
Once the public key is known, a sufficiently powerful quantum computer running Shor’s algorithm could in theory reverse-engineer the private key. That’s still a hypothetical threat — today’s quantum machines aren’t there yet — but the data shows a large chunk of the network’s value is already operating on borrowed time.
Safe Bitcoin and the road ahead
Glassnode estimates 13.99 million BTC are currently safe from quantum risk. That’s the portion locked in addresses that have never revealed a public key, mostly modern SegWit and Taproot outputs used with best practices. But the operational exposure figure is the one to watch. It’s not just a legacy problem — it’s being created every day by ordinary spending habits.
Whether the community can shift behavior fast enough remains an open question. Bitcoin’s price has slipped more than 3% in the last week, though that slide has more to do with macro headwinds than quantum anxiety. For now, the clock is ticking on a problem that doesn’t have a consensus solution yet.
