The crypto industry has spent months debating which Bitcoin wallets sit exposed to future quantum attacks. Andrew Gault thinks that conversation misses the actual emergency.
Gault, the CEO of networking firm ZeroTier and a founding partner at 7percent Ventures, has backed quantum hardware startups including British firm Universal Quantum. In a recent interview with CoinDesk, he argued that the financial system’s most dangerous vulnerability isn’t stored data at all. It’s the encrypted traffic moving between exchanges, bridges, and custodians right now, traffic that sophisticated adversaries are already collecting.
“Every interbank message, every payment authentication record, and every digital signature traveling across a network today is being collected by sophisticated adversaries who don’t need to read it yet,” Gault told CoinDesk.
The warning lands at an uncomfortable moment. Google’s Quantum AI team published research in March showing a sufficiently powerful quantum computer could derive a Bitcoin private key from an exposed public key in about nine minutes. That paper set off alarm bells about the roughly 6.9 million BTC sitting in addresses with exposed public keys. But Gault’s point is that the wallet-key fixation obscures a larger, already-underway threat.
The Harvest Now, Decrypt Later Problem
Cryptographers call it “harvest now, decrypt later.” The concept is brutally simple: adversaries don’t need a working quantum computer today. They need cheap storage and patience.
Encrypted traffic moving across the internet, including signed transactions, exchange API authentication packets, and cross-chain bridge proofs, can be captured and archived indefinitely. Once quantum hardware crosses the decryption threshold, that stored library becomes readable. The attack surface isn’t theoretical future wallets. It’s every piece of crypto-related encrypted traffic that has ever touched the open internet.
“CISOs and security teams have been trained to protect data at rest,” Gault said. “What nobody wants to say out loud is that the adversary’s strategy has changed. They’re patient, they have storage, and they’re building a library of today’s encrypted traffic to decrypt the moment quantum capability crosses the threshold.”
Google’s own security engineers have reached similar conclusions. In a March post, vice president of security engineering Heather Adkins and senior cryptography engineer Sophie Schmieg announced the company is targeting 2029 for completing its post-quantum cryptography migration. The post cited progress on quantum hardware, error correction, and factoring resource estimates.
Critically, Google said it has “reprioritized its internal threat model to focus on authentication services and digital signatures.” That’s the same wire-level signing infrastructure Gault has been flagging.
“The threat to encryption is relevant today with store-now-decrypt-later attacks,” the Google post stated.
Citi’s $3.3 Trillion Nightmare Scenario
For anyone dismissing this as academic, Citi ran the numbers in February.
The bank modeled what happens if a quantum-enabled attacker compromises a single top-five U.S. bank’s access to the Fedwire Funds Service, the Federal Reserve’s real-time gross settlement system that processes trillions daily. Their estimate: a cascade of $2 trillion to $3.3 trillion in economic damage across the U.S. economy. That translates to a 10% to 17% decline in real GDP from a single point of failure.
The Global Risk Institute, cited in the same Citi report, puts the probability of a cryptographically relevant quantum computer arriving by 2034 at between 19% and 34%. Those odds aren’t comfortable. A one-in-three chance of economy-breaking capability within eight years would normally trigger serious infrastructure investment.
For crypto, the wire-level attack surface may actually be broader than the traditional banking one. Cross-chain bridge proofs, exchange API authentication, signed transactions broadcast in public mempools, and the back-channel signing traffic between cold storage and trading desks all rely on the same cryptographic assumptions Citi was modeling.
We’ve covered the wallet-side debate extensively. Bitcoin developers floated a proposal in April to freeze coins sitting in quantum-vulnerable addresses, sparking heated debate about network intervention versus user sovereignty. But that proposal, however controversial, addresses only half the problem.
Where Bitcoin and Ethereum Diverge
Ethereum has begun a coordinated post-quantum migration. The network’s research teams have been working on quantum-resistant signature schemes, and Vitalik Buterin has discussed account abstraction pathways that could smooth the transition. None of this is deployed yet, but the roadmap exists.
Bitcoin has no equivalent public commitment.
Major crypto exchanges and custodians haven’t announced post-quantum protections for their wire-level signing infrastructure either. The industry’s public conversation remains stuck on wallet keys, specifically the 6.9 million BTC (roughly 33% of circulating supply at current prices, worth over $500 billion) sitting in addresses where the public key is already exposed on-chain.
CoinShares argued in a February report that the wallet-key fear is overstated. Their analysis suggested the actual risk is concentrated in a smaller subset of addresses. But that framing still accepts the premise that wallets are the primary attack surface.
Gault’s argument flips the priority order. If adversaries are already harvesting encrypted traffic, the damage clock started years ago. Every signed transaction, every API call, every bridge attestation that has moved across the network using pre-quantum cryptography is potentially compromised the moment a sufficiently powerful quantum computer comes online.
The Attack Surface Nobody Wants to Audit
Consider what “wire-level signing infrastructure” actually means for a crypto exchange.
When a user initiates a withdrawal, the exchange’s hot wallet signs a transaction. That signature travels across internal networks, potentially through load balancers, across data center boundaries, and onto the blockchain. The signature itself is public once broadcast, but the authentication handshakes that authorize the signing, the API calls between services, the HSM attestations, those are encrypted in transit.
If an adversary has been harvesting that traffic for years, they’re building a playbook. Which signing keys belong to which services. What the authentication patterns look like. How the cold-to-hot transfer process works. Once quantum decryption becomes possible, they don’t just get one transaction. They get the operational architecture.
The same logic applies to cross-chain bridges, which have already proven to be crypto’s most exploited infrastructure category. Bridge attestations, validator signatures, and cross-chain message proofs all move as encrypted traffic before landing on-chain. A harvest-now-decrypt-later attack doesn’t need to break the bridge contract. It needs to understand the signing key relationships well enough to forge attestations.
For readers tracking the quantum computing threat to Bitcoin, the wire-level exposure adds a layer of urgency that wallet-migration timelines don’t capture.
Google’s 2029 Deadline and What It Implies
Google’s internal target of 2029 for post-quantum cryptography migration deserves attention.
The company isn’t a crypto native, but it runs some of the world’s most sensitive authentication infrastructure (Gmail, Cloud, Workspace, Android device attestation). When Google’s security engineers say they’ve reprioritized to focus on authentication services and digital signatures, they’re describing exactly the category of traffic Gault warns is being harvested.
The 2029 target also implies Google believes quantum hardware will reach the danger zone within that timeframe. Their March post cited “progress on quantum hardware, error correction and factoring resource estimates.” Those three factors, combined, determine when a quantum computer can actually break RSA and ECC at scale.
If 2029 is aggressive but realistic for Google, what does that mean for crypto infrastructure that hasn’t started migrating?
Exchange API authentication, custodian signing workflows, bridge attestations, and the signing traffic between cold storage and trading desks would all need to transition to post-quantum cryptographic standards. That’s a coordination problem on the scale of Ethereum’s merge, except with no established governance process and entities that often treat their signing infrastructure as proprietary competitive advantage.
The potential wallet migrations we covered in April focused on user-side transitions. Infrastructure-side transitions are messier. They require coordinated upgrades across multiple counterparties who all rely on the same cryptographic assumptions.
What Actually Needs to Happen
Gault didn’t offer a specific fix, and frankly, there isn’t a simple one.
Post-quantum cryptography standards exist. NIST finalized its first set in 2024, including CRYSTALS-Kyber for key encapsulation and CRYSTALS-Dilithium for digital signatures. Google is deploying these internally. But crypto infrastructure tends to lag enterprise security practices by years, not months.
The immediate steps would include:
- Exchanges and custodians auditing their wire-level signing infrastructure for quantum vulnerability
- Bridge protocols evaluating post-quantum signature schemes for attestation
- Bitcoin Core developers beginning serious discussion of quantum-resistant transaction formats (not just address formats)
- Industry coordination on timeline expectations, so the transition doesn’t fragment liquidity across incompatible standards
None of this is happening at visible scale. The conversation remains stuck on wallet keys and address types, which are important but not the whole picture.
For traders and holders, the practical implication is uncomfortable. Your wallet seed phrase might be quantum-safe if you’ve never exposed your public key. But every exchange you’ve used, every bridge you’ve crossed, every custodian holding your assets, their signing infrastructure traffic has been traversing the open internet for years. If harvest-now-decrypt-later is real (and multiple credible sources say it is), that traffic is already in storage somewhere.
The market tracks BTC price movements on our live dashboard, but there’s no equivalent dashboard for quantum risk exposure. Maybe there should be.
The Clock Started Years Ago
The Global Risk Institute’s 19% to 34% probability of quantum capability by 2034 means the industry has, at most, eight years to complete a transition it hasn’t started. More realistically, if Google’s 2029 target reflects actual threat timelines, the window is three years.
Three years to audit, upgrade, and coordinate across hundreds of exchanges, dozens of bridges, and thousands of custodians, all of whom built their signing infrastructure on cryptographic assumptions that may have a shelf life.
Gault’s portfolio includes companies building the hardware that creates this threat. That gives him visibility into the timelines. When someone who funded the labs now threatening Bitcoin says the industry is looking in the wrong place, it’s worth listening.
The next major quantum hardware announcement, likely from Google, IBM, or a well-funded Chinese lab, will probably trigger another round of wallet-key panic. The smarter response would be to ask what’s already been harvested and whether anyone is doing anything about it.
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