As quantum computing researchers celebrate breakthrough after breakthrough, Web3’s $4-trillion asset base faces a ticking time bomb. Last December, Google announced that their quantum Willow chip performed a computation in less than five minutes that would have taken a state-of-the-art super computer ten septillion years (about 100 trillion times longer than our universe is old). Drug discovery, materials science, financial modeling, and optimization problems of all kinds will enter a golden age thanks to quantum. But most modern encryption, which relies on math puzzles that are functionally impossible for a classical computer to solve, could be cracked instantly by quantum.

In Web3, adversaries are already collecting encrypted blockchain data to crack later, when quantum comes of age. An investment in crypto is, in essence, an investment in the integrity of cryptography, which quantum computing directly threatens.

Fortunately, researchers have demonstrated that specialized zero-knowledge (ZK) cryptography can help quantum-proof the industry’s most valuable blockchains, ensuring Web3 can reap the benefits of quantum — from new antibiotics to hyper-optimized supply chains — while insulating it from the dangers.

The quantum advantage

On Oct. 22, Google published verifiable results in Nature demonstrating its quantum chip is “useful in learning the structure of systems in nature, from molecules to magnets to black holes, [running] 13,000 times faster than the best classical algorithm on one of the world’s fastest supercomputers.” What’s astonishing about these results is they were not based on a contrived benchmark, like the earlier example, but on applied problems with direct scientific benefits.

Despite quantum’s evident bounty to human knowledge, it poses an undeniable threat to cryptography in general and the nearly $4-trillion digital asset base in particular. The Human Rights Foundation published a report showing over six million BTC are in early, “quantum vulnerable” account types, including Satoshi’s dormant 1.1 million BTC. These will likely be the first “Q Day” (the day when quantum becomes powerful enough to break public-key encryption) casualties.

Both Ethereum and Bitcoin rely on Elliptic Curve Digital Signature Algorithm (ECDSA), which is famously vulnerable to “Shor’s algorithm,” a quantum algorithm designed in the 1990s for rapidly calculating the prime factors of large integers, a problem otherwise completely intractable for classical computers. It’s even theoretically possible that quantum has already broken Bitcoin; we just haven’t realized it yet.

And yet, many researchers have poo-pooed the threat. Jameson Lopp of cypherpunk fame posted on X that “the fear and uncertainty about quantum computing may very well be a greater threat than quantum computing itself.” In other words, the only thing we have to fear is fear itself. But no matter who you ask, the quantum threat is non-zero. Vitalik Buterin puts the chance of quantum breaking Ethereum at 20% by 2030. And that means we have to be prepared.

The timeline matters — a lot. Harvest now, decrypt later, moves the timeline up much earlier. Potential attackers (including nation states and hacker groups) are stockpiling encrypted blockchain data–from wallet backups to exchange custody data–to crack when quantum comes of age. Every transaction broadcast to the network, every public key exposed, becomes ammunition for future attacks. The window for implementing quantum-resistant cryptography narrows with each passing quarter.

Enter zero-knowledge

The beauty of zero-knowledge (ZK) cryptography lies in its elegance and simplicity. A prover can convince a verifier that something is true without revealing any information beyond the validity itself. As ZK technology has matured, proof times have fallen from hours to seconds, while proof sizes have shrunk from megabytes to kilobytes. The computational cost for AI in particular remains high, limiting its usefulness to high-stakes environments like Web3, traditional banking and defense.

Zero-knowledge and quantum

At first glance, it may not be obvious how zero-knowledge technology can protect blockchains from quantum attacks. Zero-knowledge proofs are privacy tools, a way to prove something is true without revealing any underlying information. But the same privacy-preserving techniques can also be built on top of quantum-resistant math, turning ZK into a broad shield for blockchains. Hash-based proofs (using zk-STARKs) and lattice-based proofs, built on problems that even powerful quantum machines struggle with, don't rely on quantum-vulnerable elliptic curves.

But quantum-resistant ZK proofs are larger and heavier than today’s versions. That makes them harder to store and more expensive to verify on blockchains with tight space limits. But the benefit is enormous: they offer a path to protect billions of on-chain assets without needing an immediate, risky overhaul of the base protocol.

In other words, ZK gives blockchains a flexible upgrade path. Instead of ripping out their entire signature system overnight, networks could gradually add quantum-safe ZK proofs to transactions — allowing old and new cryptography to coexist during the transition period.

The quantum benefit to Web3

Today’s computers can only fake randomness. They use formulas to generate “random” numbers, but those numbers are ultimately produced by a predictable process. That means parts of a blockchain system — like choosing which validator gets to propose the next block, or determining the winner of a decentralized lottery — can be subtly influenced to the financial benefit of bad actors. But earlier this year, quantum researchers achieved a remarkable milestone: certified randomness.

Quantum systems leverage natural, unpredictable phenomena such as the spin of a photon or the decay of a particle. This is genuine, unforgeable randomness, something classical computers can’t provide.

For blockchains, this is a big deal. The Web3 ecosystem needs a public, quantum-powered randomness beacon to seed the core mechanisms that make blockchains tick. With quantum, we can build one that is fair, tamper-proof, and impossible to manipulate. A solution that would address long-standing flaws in decentralized lotteries and validator selection.

Here lies the question. Will Web3 get serious about quantum-resistant cryptography before quantum computers come of age? History suggests that base layer upgrades to large blockchain protocols can take years, in part due to the lack of central coordination inherent in decentralized systems. However, the industry cannot afford to wait for quantum to break ECDSA before taking action.

We can quibble over the exact timeline, but the quantum future is an approaching certainty. ZK can protect Web3 through this transition, turning quantum threats into quantum opportunities.

The time to act is now, while we still can.