Quantum’s first crypto victims may not know they’ve been hacked

The next blow to the crypto market could trigger without an identifiable perpetrator and no apparent compromise. Christopher Smith, the CEO and co-founder of blockchain firm Quantus Network, reportedly suggested that a signal that a quantum computer has compromised the crypto security used in major blockchains may be a succession of wallet thefts that cannot be explained. The market may discover what happened only when funds from supposedly secured wallets start to move.

Therefore, while quantum risk has implications for individual projects, it is actually a market-wide phenomenon. Quantus estimates that 99.96% of the crypto market, or about $2.3 trillion in digital assets, remains vulnerable to a sufficiently powerful quantum computer. According to its State of Quantum Report published in May 2026, the timeline for preparations for the industry is rapidly approaching late this decade and early 2030s.

Additionally, migration.fail indicates major networks, including Bitcoin, Ethereum and Solana, as still dependent on signatures that are vulnerable to quantum attacks. In its report in July, Reuters revealed that none of the 20 biggest blockchains have adopted a post-quantum signature algorithm.

Why “no breach” is the tell

A quantum attacker does not have to breach an exchange or hack into the user’s equipment. Instead, a sufficiently efficient machine can derive a private key from a public key already available on-chain and use it to divert funds.

As far as investigators are concerned, everything else is okay.

“When someone cracks your key, you don’t get a memo saying how they did it,” Smith said. In a well-secured organization, he added, “the only forensic evidence would be that there was no breach.”

Security researcher Sean Cheetham of Blockchain Capital expects an attacker to start quietly rather than immediately target Satoshi Nakamoto’s dormant Bitcoin. Exchange hot wallets, he said, could be more attractive because unexpected transactions from them may not immediately trigger alarm bells.

The concern is confirmed by Google research, but this doesn’t mean that a quantum attack is going to happen in the near future. In March, Google researchers’ report estimated that breaking the 256-bit elliptic-curve cryptography that is widely used in the crypto world could be achieved by using less than 500,000 physical qubits based on their assumptions, which is about 20 times less than the earlier estimations made. Google advised blockchains to begin the transition to post-quantum cryptography.

Tether’s minting key over Satoshi’s coins

Much of the discussion around “Q-day” — the hypothetical point when quantum machines can break today’s public-key cryptography — has focused on Satoshi Nakamoto’s estimated $63 billion in Bitcoin.

Smith sees another potentially bigger market risk: Tether’s minting or issuance keys.

Should an attacker obtain access to those keys, they may be capable of generating illicit USDt, leading to a cryptocurrency breach that could result in the occurrence of a stablecoin and liquidity crisis. Tether has indicated that its key security is paramount since its private keys are responsible for USDt issuance.

The implication is broader than Tether. DeFiLlama’s latest data puts the total stablecoin market at about $300.7 billion, with Tether’s USDt accounting for roughly $183.1 billion, or 60.9% of the market. The Bank for International Settlements said dollar-backed stablecoins held more than $270 billion in assets in December 2025 and purchased about $33 billion of U.S. Treasury bills during 2025.

The increasing association with traditional finance could potentially make any disruption regarding stablecoins much more impactful, especially during periods of distress in the markets.

The timeline keeps compressing

There is no quantum device that can carry out these kinds of attacks at present, and there is still a sizable technological gap. The “Quantum Horizon” report published in June gives an estimate of the likelihood that a quantum computer which can be used for cryptographic attacks might exist in 2035 to be about one-in-six, increasing to around 30% by 2040, and 60% by 2050. The authors caution that these are forecasts rather than predictions.

Yet, the issue of migration cannot be sidestepped any longer. Google expressed in March that it intends to finish its own switch to post-quantum cryptography in 2029 due to advances in quantum hardware and error correction.

The migration of crypto is particularly challenging due to the decentralized, public, and difficult-to-update nature of blockchains. More so, post-quantum signatures are much bigger than traditional signatures. The migration.fail site shows that classical ECDSA signatures take up about 64 bytes while Dilithium-5 signatures take up around 4,595 bytes, which is huge and can increase the amount of data being stored, transmitted, and the costs involved in transactions.

As a result, the industry is under pressure to beat the clock. For investors, the greatest danger might not stem from the day when quantum computers unambiguously defeat Bitcoin or Ethereum. Instead, it could be the day when people observe dubious transfers from major wallets, exchanges, or stablecoin operators and suddenly realize that those cryptographic assumptions used to protect billions of dollars may have already been compromised.