Quantum Computing Threatens Blockchain — But the Real Problem Goes Beyond Stolen Keys

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Most of the conversation around quantum computing and blockchain security has focused on one question: how do you stop a quantum computer from breaking cryptographic private keys in the first place? But NEAR Protocol's chief technology officer Anton Astafiev is raising a concern that has received far less attention — what happens after a quantum attack has already occurred? If a sufficiently powerful quantum computer were used to derive a private key and drain a wallet, blockchain protocols would have no reliable way to distinguish whether the transaction was made by the rightful owner or by a thief who reconstructed the key. "We won't be able to tell if someone running a transaction is the rightful owner of the asset or not," Astafiev said, framing the post-attack verification problem as one of the most difficult challenges the industry has yet to seriously address.The stakes of getting this wrong are significant.

Astafiev warns that in such a scenario, protocols would face a stark binary choice: freeze all potentially compromised wallets — locking out legitimate owners along with attackers — or do nothing and allow the blockchain to descend into what he called a "wild west" of unverifiable ownership. His proposed solution is zero-knowledge proof technology, which could theoretically allow the rightful owner to prove they know the original seed phrase behind a wallet without exposing any sensitive information in the process. This approach would create a cryptographic ownership verification system that remains secure even in a post-quantum environment, giving protocols a mechanism to distinguish legitimate recovery attempts from theft without requiring users to reveal the very credentials that are under threat.

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Everyone asked how to prevent quantum attacks, NEAR's CTO asked what happens after one succeeds, the question was overdue