Q-day won't knock: When quantum hackers steal your crypto, the only clue is no clue at all 🕵️

The first sign that quantum computing has broken modern cryptography is unlikely to be a splashy theft of Satoshi Nakamoto's dormant Bitcoin, according to Christopher Smith, CEO and co-founder of Quantus Network. Instead, Smith told Cointelegraph, victims could see a wave of unrelated crypto wallet breaches with no trace of how an attacker did it. "When someone cracks your key, you don't get a memo saying how they did it," Smith said. A sufficiently powerful quantum computer could derive a private key from public keys exposed onchain, allowing funds to be moved without compromising a wallet, device or exchange's internal systems. In a theft involving a highly secure organization, "the only forensic evidence would be that there was no breach," Smith added.

Smith said the first targets are more likely to be military systems and state secrets, while crypto attackers could pursue even more valuable keys. "If I'm focusing on blockchain, what's the single most valuable key? It's probably Tether's minting key," Smith said. A quantum attacker could mint tokens from an administrative wallet and sell them before the issuer could respond. USDT is a multi-chain stablecoin, and some of the networks on which it operates are already working on post-quantum migration.

Security researcher Sean Cheetham of Blockchain Capital said attackers would likely target hot wallets at exchanges "that aren't going to ring alarm bells rather than stealing Satoshi's coins," worth $63 billion at the time of writing. Smith added that an attacker may disguise a quantum theft as an ordinary compromise, offering "plausible, deniable" explanations such as a user losing their keys.

The arrival of "Q-day," a hypothetical moment when quantum computers become powerful enough to break standard public-key cryptography, is difficult to pin down. In March, Google accelerated its post-quantum migration timeline to 2029 after an AI-assisted breakthrough showed elliptic curve cryptography can be cracked with far fewer physical qubits than previously forecasted. NGRAVE CEO Roy Blackstone said earlier quantum forecasts failed to account for the parallel development of artificial intelligence, which has accelerated breakthroughs sooner than many threat models anticipated.