The first sign that quantum computing has breached modern cryptography likely won't be a high-profile theft of Satoshi Nakamoto's dormant bitcoins. The founder of the blockchain startup Quantus suggests it will be a wave of seemingly unrelated crypto wallet hacks with no trace of malicious actor activity.
"When someone hacks your key, you don't get a note explaining how they did it," Quantus Network CEO and co-founder Christopher Smith told Cointelegraph. A sufficiently powerful quantum computer could calculate a private key from public keys disclosed on-chain. This would allow a malicious actor to move funds without hacking the wallet's internal systems, device, or exchange.
Therefore, the arrival of "Q-day" — the hypothetical moment when quantum computers can break standard public-key cryptography — will be particularly difficult to detect. If a well-protected organization is attacked, "the only forensic evidence would be the absence of a hack," Smith said.
Smith's warning follows advances in quantum algorithms that have lowered the estimate of computational resources needed to attack the elliptic-curve cryptography used by major blockchains.
First Targets May Not Be Satoshi's Bitcoins
Much of the crypto community's fear surrounding Q-day revolves around the potential hacking of keys protecting the presumed bitcoin assets of Satoshi Nakamoto, valued at $63 billion at the time of writing. They could suddenly be dumped onto the market.
According to Smith, the first targets could be military systems and state secrets, with quantum attackers choosing keys of even greater value.
"Focusing on blockchain, which key has the highest value? Probably the Tether issuance key," Smith said. A quantum attacker could mint tokens out of thin air from the administrative wallet and sell them on the market before the issuer could react, he said.
USDT is a multichain stablecoin. Some networks where it is used are already actively transitioning to post-quantum solutions.
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Another scenario suggests attackers would start with a less conspicuous step.
Blockchain Capital security researcher Sean Chittham believes an attacker would more likely target exchange hot wallets, "which wouldn't raise alarms, rather than stealing Satoshi's coins."
Smith suggested an attacker might disguise a quantum theft as a conventional compromise.
"There's an alternate scenario where they... will have plausible explanations allowing them to deny everything: 'Oh, someone just somehow lost their keys,'" he said.
Q-Day Timeline Hard to Pin Down
In March, Google accelerated its shift to post-quantum solutions to 2029 following a breakthrough using AI. It showed that elliptic-curve cryptography could be broken with far fewer physical qubits than previously predicted.
NGRAVE CEO Roy Blackstone stated that previous quantum forecasts failed to account for parallel AI development.
"Most threat models assumed we were over a decade away from the moment quantum technology could break the cryptography protecting public keys. But they didn't account for how fast AI would develop alongside it."
Despite growing concern, there is no consensus on the timeline for creating a quantum computer capable of breaking modern cryptography.
Smith, whose company has been developing a quantum-resistant blockchain network since its launch, estimated the probability of this happening by 2028 as "50/50." In his view, improvements in quantum algorithms and AI-assisted hardware research make predictions less reliable.
Chittham called the early 2030s a "practically inevitable" timeline, with an earlier arrival being "more of a tail-end probability."
Solana Foundation Chief Information Security Officer Michael Coates declined to estimate a timeline in an earlier interview, stating, "There's no way to know that."
"If you talk to people in the industry, it's always five years away — they've been saying that for 10 years or even longer. Maybe it's four years now," he said. However, Coates added, uncertainty is no reason to delay action.
"Fortunately, blockchains aren't waiting and have already begun transitioning to post-quantum signatures," Blackstone said. "Without that, the damage would be catastrophic."
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