A new report from blockchain data firm Glassnode warns that nearly $500 billion worth of Bitcoin — a substantial chunk of the existing supply — is vulnerable to future quantum computing attacks. The firm mapped the cryptographic exposure of Bitcoin's unspent transaction outputs and found that a large portion relies on older address formats and signature schemes that could be broken once quantum computers reach sufficient power. Exchanges, in particular, were flagged as a major weak point in the chain's security.
What Glassnode found
Glassnode's analysis looked at the entire Bitcoin supply and assessed which coins sit in addresses that use the earlier P2PK (pay-to-public-key) format or have exposed public keys. Those coins are the most susceptible because a quantum attacker could in theory derive the private key from the public key. The nearly half-trillion-dollar figure represents the current market value of those exposed coins. The firm didn't name specific exchanges, but it stressed that any platform holding large amounts of Bitcoin in hot wallets with legacy addresses is a prime target.
Why exchanges are a weak point
Exchanges often keep significant balances in addresses that have publicly known keys — either from old withdrawal patterns or from reused addresses. That makes them a more attractive target than, say, a cold storage wallet that has never broadcast a transaction. Glassnode noted that if a quantum attack became feasible, an exchange's hot wallet could be drained before the network even had time to react. The timing isn't great: several major exchanges are still migrating away from legacy address formats, but the process is far from complete.
How far off is the threat?
Glassnode didn't put a timeline on when quantum computers might pose a real danger, but the report is a wake-up call for an industry that tends to think in five-year increments. Bitcoin's cryptography — ECDSA and SHA-256 — is considered safe for now, but the sheer value at risk means the window for upgrading address standards is narrower than many assume. Developers have discussed quantum-resistant signature schemes like Lamport signatures for years, but no concrete upgrade has been adopted on mainnet.
What comes next
The next concrete step is likely a push from Bitcoin Core developers to accelerate the adoption of taproot and other modern address types that don't expose public keys until a transaction is spent. Some exchanges have already started moving funds to bech32 addresses, but the Glassnode data suggests a lot of work remains. The question is whether the industry will treat this as a theoretical risk or start treating it as a deadline.
