BlackRock has entered the quantum computing debate with a new report warning that future advances could eventually threaten the cryptography securing Bitcoin, Ethereum and much of the broader digital asset market. The company’s central message is not that blockchains face an immediate crisis, but that the industry must begin post-quantum migration before “Q Day” becomes a full-blown security event.
The report, titled “Quantum Computing and Blockchains,” was authored by Will Su, head of digital assets research at BlackRock, Inish Crisson, senior software engineer at Aladdin Digital Assets Lab, and Robert Mitchnick, head of digital assets at BlackRock. It presents quantum computing as both a cybersecurity risk and a potential test of blockchain governance, particularly for networks that rely on elliptic curve cryptography for transaction signatures.
“Quantum computing has received increasing attention in recent years, particularly because of its implications for blockchains and many other elements of modern cyber infrastructure,” the authors write. “In our view, quantum computing is likely to pose a manageable risk to blockchains, subject to the industry’s ability to quickly and proactively transition to post-quantum cryptography in the coming years.”
The main risk of Bitcoin and Ethereum
BlackRock points out that no cryptographically functional quantum computer, or CRQC, exists today. But he indicates that the deadlines have changed. The report notes that Google has pushed back its post-quantum migration deadline to 2029, while IBM is targeting large-scale fault-tolerant quantum computing between 2029 and 2033.
The main problem is not Bitcoin’s proof-of-work engine. BlackRock claims that Bitcoin’s SHA-256 hash function is “widely considered quantum-resistant,” with Grover’s algorithm only offering a quadratic speedup that could be absorbed by Bitcoin’s difficulty adjustment. The most relevant attack surface is ownership: the digital signatures that prove control of the coins.
Bitcoin and Ethereum currently rely on elliptic curve cryptography for key ownership and transaction authorization. According to the report, classical computers would need millions or even billions of years to break 256-bit ECC. A sufficiently powerful quantum computer using Shor’s algorithm could change this equation by turning private key recovery into a more tractable mathematical problem.
“The foundations of modern cryptography are being challenged in the quantum world,” BlackRock wrote. “This is not because quantum computers run faster. Rather, QCs are particularly effective at discovering hidden patterns in large data sets by exploiting the unique properties of quantum physics and employing quantum algorithms to solve classically infeasible problems like ECDLPs in just a few days or minutes.”
Bitcoin migration is simpler, but coordination is difficult
For Bitcoin, BlackRock says the technical scope of a post-quantum upgrade is narrower than for many other systems, because the main task is replacing a digital signature algorithm. The most difficult problem is that of social coordination within a decentralized network that deliberately avoids rapid or centralized changes.
The report states that nearly 7 million BTC, or approximately 35% of the circulating supply, could be vulnerable to long-range quantum attacks because public keys have already been exposed. This figure includes 1.9 million BTC in address types that expose unhashed public keys and an additional 5 million BTC in reused addresses that revealed public keys in previous transactions while holding UTXOs.
BlackRock also highlights the unresolved debate around inactive or lost coins. He cites estimates from Chainalysis that 2.3 to 3.7 million BTC, or 11 to 19 percent of the circulating supply, could be permanently lost. This includes approximately 1.1 million BTC in P2PK addresses widely believed to belong to Satoshi Nakamoto.
“In our opinion, PQ migration for cryptocurrencies is quite feasible from a technical point of view, and the main challenge is that of coordination and timely implementation,” the report said. “The end-to-end process of building consensus around PQC protocols and timing, implementing upgrades on the blockchain, and making orderly migrations across the ecosystem will likely be a multi-year effort.”
Ethereum has a roadmap, but more moving parts
The situation with Ethereum is different. BlackRock says the network has a more clearly defined migration path, guided by the Ethereum Foundation, but faces greater technical complexity due to its proof-of-stake architecture, smart contract environment, data layer and zero-knowledge application layer systems.
The report cites four Ethereum vulnerability areas identified by Vitalik Buterin in early 2026: BLS signatures in the consensus layer, KZG proofs in the data layer, external account signatures, and zero-knowledge proofs in the application layer. In simpler terms, validator voting, data verification, user transactions, and application-level proofs all touch on quantum vulnerable cryptographic assumptions.
BlackRock highlights Ethereum’s “L1 Strawmap,” a proposed sequence of seven network updates and hard forks between 2026 and 2029, five of which directly address quantum vulnerabilities. These include native account abstraction, post-quantum signature precompilations, post-quantum validation keys, hash-based consensus signatures, and a longer-term shift from KZG commitments to STARK-based verification.
A wall of worry for crypto
BlackRock’s conclusion is measured. The report does not present quantum computing as an imminent existential threat to Bitcoin or Ethereum. Rather, he argues that quantum risk is one of the few remaining “walls of concern” for digital assets, and that successful post-quantum migrations could strengthen the sector over time.
“The global cybersecurity infrastructure is at an important inflection point as quantum computing advances,” the authors write. “Digital assets, notably Bitcoin and Ethereum, are technically positioned for migration; a more difficult problem is coordinating timelines and deploying upgrades across decentralized networks in an orderly manner. That said, there is much less eagerness to upgrade current cryptosystems, including Bitcoin, Ethereum and others, to a quantum security standard than to build a CRQC from the current state of progress in quantum computing.”
At press time, BTC was trading at $62,629.
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