Bitcoin Q-Day: quantum threat seen in early 2030s as Lopp warns upgrade work is already late

27 Oct 2026

27 Oct 2026, 17:05 UTC+01:00

Bitcoin TradeReviewed News Desk

Bitcoin’s Q-Day, the moment a quantum computer could break its signatures, may still be years away, but two well-known voices say preparation is already behind schedule. Casa security chief Jameson Lopp argues a Bitcoin-breaking machine is orders of magnitude away, while Oxford quantum computing lecturer Stefano Gogioso puts Q-Day in the early-to-mid 2030s, BeInCrypto reported on Tuesday.

How far is the hardware?

Google’s Willow chip runs on 105 qubits. In March, Google estimated that cracking Bitcoin’s signatures would need fewer than 500,000 qubits, a gap of more than 4,700-fold. Lopp says several large breakthroughs would be needed to close it, though he warns that AI progress could spill over into quantum research. The threat targets Bitcoin’s elliptic-curve signatures (secp256k1), not the SHA-256 hashing used in mining, where quantum speedups are much weaker.

Gogioso, who co-founded quantum-money startup Spooqy, defines Q-Day as the point when secp256k1 can be broken within one block, about 10 minutes. “Our forecasting models set it to the early/mid 2030s based on current technology trends,” he wrote on X on Oct. 24.

Governance is the bottleneck

Both experts point to Bitcoin’s slow decision-making rather than physics. “I’m still hopeful that we have at least a decade or more, because if we have less than a decade, we’re behind,” Lopp said. He co-authored BIP-361, a draft proposal to phase out quantum-vulnerable signatures over several years, but does not expect serious calls to activate it unless a capable quantum computer looks less than 10 years away. Gogioso’s forecast already falls inside that window.

Migration itself is slow: Chaincode Labs estimates a full upgrade could take five to 15 years, according to Lopp’s September essay.

Which coins are most exposed

Coins whose public keys are already visible on-chain are the easiest targets. That includes early pay-to-public-key (P2PK) outputs, reused addresses and Taproot outputs. Lopp estimates about 2.6 million BTC, roughly 13% of supply and worth around $207 billion, may never migrate. Coinbase, which holds about 12% of all BTC, published a post-quantum readiness plan in October, but the protocol still has no agreed deadline.

What it means for traders

• No near-term panic: neither expert sees a threat to Bitcoin today, so quantum headlines driving sharp selloffs look like noise for now.
• Watch BIP-361: any move toward activation or a freeze on vulnerable coins would be a major event for supply and sentiment.
• Custody hygiene: avoiding address reuse limits public-key exposure, and exchange custody choices matter as platforms publish quantum plans.

To compare security and custody across platforms, see our crypto exchange comparison, our BingX review (our number one pick) and OKX review (number two), and our how we test methodology. Beginners can start with where to buy your first Bitcoin. This is not financial advice.

Related reviews

• Bingx review
• Okx review

Sources

• BeInCrypto: Is Bitcoin's Q-Day a Decade Away? Even Skeptics Say It's Running Late

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