Google researchers said advances in quantum computing could make today's blockchain encryption vulnerable as early as 2029, accelerating the industry's timeline for preparing new security standards.

The finding has rattled a $2T crypto market that has already suffered repeated hacks using conventional computers.

Quantum computing uses the principles of quantum physics to perform certain calculations far more efficiently than conventional computers. If that capability advances as expected, it could undermine the cryptographic keys that secure cryptocurrency ownership and transactions.

After a public key appears on the blockchain, a sufficiently advanced quantum computer could theoretically reverse-engineer the matching private key and access the wallet.

Bitcoin is considered particularly exposed because its 17-year transaction history has generated a large number of visible public keys.

Roughly 35% of Bitcoin's circulating supply is vulnerable, according to an unpublished June 2026 working paper. A separate estimate from crypto finance firm Galaxy Digital put the dollar figure at roughly $470B.

Crypto transactions are irreversible, and Bitcoin has no central authority to freeze accounts or issue refunds. One major theft could tank token prices across the market, Cristiano Ventricelli, vice president and senior analyst of digital assets at Moody's Ratings, told Reuters.

The upgrade problem is political

None of the top 20 blockchains have implemented a post-quantum signature algorithm, according to industry executives.

Upgrading requires a decentralized community to agree on a technical fix, coordinate millions of specialized computers, and fund a potentially years-long transition.

Researchers and executives have compared the scale of work to the Y2K overhaul, which cost more than $300B globally.

Post-quantum cryptography also comes with its own tradeoffs. The new digital signatures are significantly larger than traditional ones, raising storage and bandwidth costs.

For Bitcoin, which has fixed block-size limits, that creates real engineering constraints, Zach Pandl, head of research at Grayscale, told Reuters, though he said he's confident solutions exist.

The Ethereum Foundation is targeting 2029 for full quantum protection. The Algorand Foundation published a post-quantum roadmap recently and plans to support post-quantum accounts later this year. Bitcoin developers remain divided on which fix to adopt and when.

Coinbase GlobalCOIN

has established an advisory board to study the technology's impact on blockchains. StrategyMSTR

set up a program to address quantum-related risks on its more than $50B Bitcoin holdings.

Christopher Wood, global head of equity strategy at Jefferies, removed a 10% Bitcoin allocation from his model portfolio earlier this year, citing the quantum threat as an existential long-term risk.

The industry's window to act is narrowing, and the hardest part isn't building the fix — it's getting a leaderless network to agree on one.