Talking about quantum computers no longer sounds like science fiction at crypto events. At a recent developer gathering at ETH Denver, engineers and security researchers focused on a simple but troubling question: What happens to Bitcoin if a powerful quantum machine comes online?
Reports have revealed that new proposals are being incorporated into the network improvement process, laying the groundwork for defenses before a real crisis emerges.
Quantum computing: why hashing is not the main fear
Hashing (what miners and many parts of the system use) is only a little faster thanks to quantum tricks. According to the work of Lov Grover, a quantum search method gives a square root speedup, which modifies the safety margins but does not erase them.
In short: to break hashes on a large scale, enormous machines would be required, perhaps unrealistic in current models.
Signatures face real risk
Reports indicate the biggest concern is signings. “What we’re worried about over the next five years is signings, and that goes hand in hand with Shor’s,” Hunter Beast, co-author of BIP 360, said at the ETH Denver gathering.
The calculations behind most current wallets rely on elliptic curves, and Peter Shor showed how a quantum machine could reverse these calculations.
This is how a public key could reveal a private key once the appropriate hardware exists. A blockchain security company tracks addresses that have already exposed their public keys, and the numbers aren’t small.
The listing from blockchain cybersecurity firm Project Eleven flags millions of coins that, if an attacker had a large enough quantum device, would be at risk.
How close are we?
Estimates have evolved. Older papers put the necessary resources into several million qubits. More recent research from groups like Iceberg Quantum suggests that figure could be much lower, perhaps in the six-figure range.
Yet the raw number of qubits only tells part of the story. What matters is how many “logical” qubits you can run with acceptable error rates, how long the calculations take, and whether the machine can remain stable during that time.
The laboratory stages of large companies are also important; for example, Google reported progress in fixing errors that many found encouraging. This doesn’t mean a break-in is imminent, but it does change risk models.
Where is the industry?
Reports indicate that teams are forming to study and build defenses. The Ethereum Foundation has a post-quantum group, and major exchanges and companies are participating in the discussions.
Coinbase has advisors in place and its CEO, Brian Armstrong, said the problem can be solved through planning. It’s “solvable,” he said.
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