7M Bitcoin at Risk as Quantum Computing Set to Break Crypto in 3 Years | Interview

A day is coming when quantum computing will “rip to shreds” the security systems on which Bitcoin — and crypto as a whole — is built.

That day, dubbed “Q-Day”, is “right at our doorstep,” at most five years from now, could be earlier, according to David Carvalho, the founder, CEO, and chief scientist of decentralized post-quantum infrastructure protocol Naoris.

In this interview with Cryptonews, Carvalho talks about the quantum threat to traditional cryptography and how quickly such computers could dismantle Bitcoin’s security walls, which, until now, have been thought unbreakable.

The ex-ethical hacker predicts that 30% of all BTC in circulation could be at risk of theft when “Q-Day” arrives. Carvalho also discusses ways to quantum-proof the network, BTC wallets, and corporate/nation-state holdings.

Cryptonews: In your view, how imminent is “Q-Day”, and what recent developments make you believe quantum computers could break existing cryptography in 3 to 5 years?

David Carvalho: Q-Day is not some far-off sci-fi scenario – it’s already at our doorstep. Then, this year’s Majorana chip breakthrough from Microsoft was solid proof that we can make stable, scalable quantum processors.

Google Quantum AI has projected that quantum computers with sub-million-qubits and capable of factoring RSA-2048 keys in a feasible time scale are around the corner.

In the meantime, we already have around 100 small quantum systems up and running around the world, and consulting firm McKinsey predicts that number will rise to around 5,000 by 2030.

All together, this points to a window of three to five years — possibly even shorter — before quantum can regularly defeat today’s elliptic-curve or RSA-based cryptography.

But when IBM.’s Jay Gambetta says, “The quantum threat is not on the horizon, it’s upon us,” you realize it’s time to start paying attention.

CN: Are there any particular signals that the crypto industry should watch for to know that quantum threats are no longer theoretical but immediate?

DC: When error-corrected quantum processors with dozens or hundreds of logical qubits are being demonstrated publicly, when IBM, Google, and Microsoft keep upping their qubit-scaling targets each year, when entities like NIST and the NSA bring their post-quantum deadlines in from 2030 – that’s when you’ll know the threat is real.

But the loudest alarm bell is “harvest now, decrypt later,” with adversaries storing today’s encrypted data and killing time until quantum finally solves the code.

BlackRock raising a red flag about quantum risk in its Bitcoin-ETF filing is another obvious signal: Institutional investors are not sleeping on this.

30% of Bitcoin in Circulation Could be Stolen

CN: Why do you believe Bitcoin and other blockchains (including EVM chains) are especially vulnerable to quantum attacks in the near future?

DC: Blockchains are based on elliptic-curve signatures, which Shor’s algorithm will rip to shreds in seconds once you have a quantum computer. Every on-chain public key that is ever shown on the blockchain will forever be a target. Due to the ledger’s immutable nature, once it is revealed, you are potentially vulnerable forever.

Also, a quantum miner would be able to quickly solve proof-of-work puzzles, and you’ve got mass theft and consensus collapse looming on the horizon.

CN: Can you quantify how much of the current Bitcoin supply is at risk if a sufficiently powerful quantum computer emerges?

DC: About 30% of all the BTC in circulation (6-7m) is sitting in addresses that contain public keys directly (P2PK or reused-P2PKH). The moment a powerful quantum rig is running, those coins are fair game.

CN: What would a real-world quantum attack on Bitcoin look like? What would it mean to the retail Bitcoin/crypto investor, and can they prepare for such an eventuality?

DC: Imagine an attacker who searches for any public key in the UTXO set, runs Shor’s algorithm on a quantum machine, and then immediately moves all those UTXOs into their wallet.

For regular investors, the playbook is simple: move any coins from addresses whose keys you’ve ever revealed to fresh, quantum-safe ones; keep your wallet software up-to-date for post-quantum signing; and rely on custodians dedicated to quantum security.

CN: Why are wallets and endpoint devices considered the weakest link in the quantum era, and what specific risks do they face?

DC: Endpoints — like your phone, your laptop, any device that stores or generates your keys — harbor numerous security vulnerabilities: malware, firmware bugs, supply chain attacks. Today, attackers can already exfiltrate key material.

The classical computer can’t use it, but a quantum adversary converts that stolen key into instant access as soon as they reach a high enough qubit count. Which is to say, no matter how bulletproof the blockchain upgrade, all it takes is an insecure endpoint that hands an attacker the master key.

CN: Are there practical solutions, such as quantum-safe wallets or zero-knowledge proofs, that can protect users without sacrificing usability?

DC: There are real, user-friendly fixes: Post-quantum wallets are already in development — they will use lattice or hash-based signature schemes, but as a user, they will work just like your favorite mobile wallet.

Zero-knowledge rollups are equally interesting: they can render on-chain signatures into concise, quantum-safe proofs, so transaction flows and interfaces stay almost identical while the underlying security is now future-proof.

Preparing for a Post-Quantum Future

CN: Can Bitcoin truly upgrade to quantum-resistant cryptography without resorting to a hard fork?

DC: Replacing ECDSA with a lattice — or hash-based algorithm at the protocol level requires a hard fork — it’s just how the consensus mechanism works.

Quantum-resistant defenses are available today and can already be established through hybrid sidechains, layer-2 channels, or off-chain dual-signature schemes, deploying quantum-safe rails well before the main chain makes the transition.

CN: How can companies like MicroStrategy or governments (e.g, El Salvador or Bhutan) start the transition to quantum-safe infrastructure without causing fragmentation or disrupting existing Bitcoin services?

DC: It all boils down to a phased and collaborative playbook: Pilot dual-signature transactions. A good starting point is to issue transactions that combine today’s ECDSA signatures and a post-quantum proof side by side.

That means everything you’re doing is still valid under current rules, but you’re already testing and deploying quantum-safe rails in parallel.

Form joint working groups: Get corporations, custodians, exchanges, wallet developers, and even multiple governments to agree on clear migration roadmaps, compliance milestones, and shared tooling, so everyone can follow a similar roadmap and no sector is left behind. Run emergency-fork drills on testnets. Treat the hard fork to the quantum-safe rules as an emergency measure: practice stopping or pausing the network, flipping on the new validation logic, and resuming operations in a controlled environment. Then, when it’s time to do it live, you’ll have a way to go from zero to quantum-resilient in days, not months. Phased rollout and education: Blend technical pilots with large-scale stakeholder education — ensuring exchanges, custodians, institutional treasuries, and retail wallet providers are all aware of upgrade paths, integration steps, and fallbacks. By phasing these steps — dual signatures first, governance next, and fork rehearsals last — large holders and public issuers can harden their Bitcoin infrastructure against Q-Day without the need for ecosystem fracturing or service disruption.

CN: What are the regulatory, compliance, and cross-border challenges in implementing quantum-safe standards across blockchain networks?

DC: Algorithm standardization: So, as with TLS versions, it is also up to stakeholders all over the world to find consensus on which post-quantum algorithms are acceptable and strong.

Policy harmonization: There are export controls, laws for cryptography, and national security imperatives that vary by jurisdiction. We need diplomatic and industry coordination to avoid a patchwork of rules that don’t work together. Synchronized timelines: Node operators, exchanges, custodians, wallet providers, and end users must move to quantum-resistant protocols in harmony. If any sector lags, it risks becoming the weak link. We cannot risk any critical group falling behind.

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