More than 6 million Bitcoin — roughly one out of every three coins ever mined — are vulnerable to a future quantum computer attack, according to data from Glassnode. The analytics firm's latest report puts the number at 6.04 million BTC, a figure that underscores the urgency of updating Bitcoin's cryptographic backbone before the technology to break it becomes real.
What the numbers mean
Glassnode didn't sugarcoat it. The firm estimates that 6.04 million Bitcoin sit in addresses that use older, quantum-vulnerable signature schemes. That's a lot of coins. For context, the entire circulating supply is about 19.5 million. So roughly 31% of all Bitcoin are exposed.
The threat isn't here yet. Today's quantum computers aren't powerful enough to crack ECDSA, the elliptic curve signature scheme Bitcoin uses. But the timeline keeps shrinking. Researchers at several labs have hinted at practical quantum attacks within a decade. For a system that moves slowly and values immutability, that's no longer a far-off problem.
Bitcoin's security model relies on the assumption that no one can forge a signature. If someone could, they'd steal coins from any exposed address. The 6.04 million figure includes coins in P2PK (Pay-to-Public-Key) addresses — the oldest type — plus some P2PKH addresses that have never moved. Coins that have been spent since 2012 likely use newer, safer address types.
The exposed stash is mostly old. Some of those addresses date back to Satoshi Nakamoto's era. That doesn't make them less valuable, just harder to defend. Moving those coins would require the private key holder to sign a transaction — and if they do it in the clear, a quantum adversary might capture it.
What can be done
The fix is a new signature scheme. Developers have been working on proposals like Schnorr signatures — already activated via Taproot in 2021 — and more advanced post-quantum candidates. But adoption is slow. Not all wallets support Taproot. And most of the 6.04 million Bitcoin sit in addresses that can't simply be upgraded; the coins need to be moved to new, quantum-resistant addresses by their owners.
That's the hard part. Many of those old addresses belong to people who lost their keys, or to entities that are defunct. Others belong to early adopters who may not be watching the news. Glassnode's report is essentially a wake-up call: start moving your coins, or risk losing them when the math breaks.
The Bitcoin network itself is likely to implement a soft fork for post-quantum signatures at some point. But that process takes years of debate and testing. In the meantime, the clock is ticking on 6.04 million coins.
