Bitcoin, Ethereum 'Q-Day' Quantum Threat Could Arrive as Soon as 2030: Report

The report estimates that approximately 6.9 million Bitcoin—about one-third of the total possible supply—sits in addresses whose public keys have already been exposed on-chain, making them potentially vulnerable to quantum attack. On Ethereum, the exposure is even broader: analysts have found that over 65% of all ETH is held in quantum-exposed addresses.

What makes blockchains particularly vulnerable, the report explains, is that their public ledgers and bearer-instrument design offer no safety net. Unlike a bank, a blockchain has no fraud department, no chargeback mechanism, and no way to reverse a forged transaction. Once a quantum attacker recovers a private key and drains a wallet, the loss is permanent.

The migration challenge is compounded by the slow-moving nature of blockchain governance. The Bitcoin SegWit upgrade—a relatively modest protocol change—took more than two years from proposal to activation, and triggered a contentious chain split. Ethereum's transition to proof-of-stake required roughly six years of development. A quantum migration would touch the most fundamental cryptographic layer of any blockchain protocol.

Even under the most optimistic assumptions, the report estimates that migrating all Bitcoin UTXOs (or unspent transaction outputs) to quantum-resistant addresses—if 100% of block space were dedicated to that effort—would take approximately 76 days. As migration competes with ordinary economic activity, timelines extend significantly.

The rest of the technology world has already begun moving. Over half of all human web traffic is now post-quantum encrypted, according to Cloudflare data from December 2025. OpenSSH defaults to post-quantum key exchange, while Apple enabled hybrid post-quantum support across its devices in iOS 26. The National Security Agency has set a 2030–2033 target for complete migration across government systems.

The digital asset industry, by contrast, has barely started. Bitcoin developers are weighing numerous proposals, both formal and otherwise, while the Ethereum Foundation has formed a team that’s working to design and coordinate the network’s path to post-quantum security. But as noted, those plans could take years to execute, once developers agree upon any approach.

"The internet has already moved," the report concludes. "The digital asset industry—which arguably has more at stake because blockchains directly protect bearer value with the exact cryptographic primitives that quantum computers threaten—has barely started."

The authors recommend that blockchain networks begin immediate cryptographic inventories, deploy post-quantum key exchange in off-chain infrastructure without delay, and start the complex governance and design work needed for on-chain signature upgrades—warning that by the time the threat feels urgent, there will no longer be enough time to respond.