Wall Street research firm Bernstein is pushing back on alarm over quantum computing’s threat to Bitcoin, framing the challenge as a scheduled protocol evolution rather than a crisis in waiting.
In a note to clients on Wednesday, analysts led by Gautam Chhugani acknowledged that cryptographically relevant quantum computers (CRQCs) pose a genuine challenge to Bitcoin and the broader digital asset ecosystem — but stopped short of treating that challenge as an emergency. The team estimates Bitcoin and other crypto protocols have three to five years to implement post-quantum security measures, a window they describe as sufficient given current technical and cost constraints.
The note arrives in the wake of fresh research from Google, which last month published a paper showing that future quantum machines could break the elliptic curve cryptography underpinning Bitcoin’s transaction signatures with fewer resources than earlier models suggested.
Google’s team estimated the barrier could fall below 500,000 physical qubits — a reduction of roughly 20 times compared to prior estimates. The finding drew attention to a narrower category of risk: so-called “on-spend” attacks, where a transaction’s public key is exposed in the mempool before confirmation, creating a brief window of potential vulnerability.
Bernstein’s analysts did not dismiss Google’s findings. “Recent breakthroughs seem to have accelerated the timeline, as the challenge is no longer ‘a decade away’ as thought earlier,” the analysts wrote.
At the same time, they noted that scaling from tens of logical qubits to the thousands required for a real attack involves breakthroughs across hardware, error correction, and manufacturing — dimensions that remain unsolved.
“Quantum timelines may still be more optimistic than reality,” the note cautioned.
The firm placed particular weight on cost and scalability constraints, suggesting the transition could run into the tens to hundreds of billions of dollars. Those figures, they argued, point toward preparation time rather than panic.
Bitcoin has evolved and will continue to do so
Bernstein also identified well-capitalized institutional players — Strategy, BlackRock, and Fidelity — as likely to take a “constructive role” in reinforcing security standards. That framing reflects a broader shift in how the Bitcoin ecosystem has evolved: institutional ownership has given the network stakeholders with both the resources and the incentives to support defensive upgrades.
Not all risks are equal. Chhugani pointed to an estimated 1.7 million BTC sitting in Satoshi-era legacy wallets as the highest-exposure segment.
These addresses have permanently visible public keys, making them defined targets under certain attack models. For newer protocols and wallet structures, the exposure is more contained — dependent on specific unsafe practices that the developer community is working to address.
The emerging consensus, shared by both Bernstein and Google’s own research team, points toward 2029 as a target for post-quantum cryptography migration.
BIP 360, a draft proposal already in experimental implementation, introduces transaction formats designed to reduce exposure to vulnerable cryptographic assumptions.
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