The quantum clock is ticking: it’s Bitcoin’s problem, not Ethereum’s
A recent research note published by Citi analysts reached a conclusion about quantum risk that should give every institutional bitcoin holder pause, Tabar explains.
That finding echoes the landmark paper released in late March by Google Quantum AI in collaboration with Stanford University and the Ethereum Foundation, which found that the computing resources required to break bitcoin’s foundational cryptography are approximately 20 times lower than previously estimated. A sufficiently advanced quantum computer, operating with fewer than 500,000 physical qubits, could derive a bitcoin private key from its public key in roughly nine minutes. That machine does not exist today. But the window to act responsibly is narrowing faster than most institutions realize. When Google raises the alarm, and Citi confirms it in the same quarter, this is no longer a fringe concern. This is the silver bullet. And it points directly at bitcoin.
Why bitcoin is exposed
Bitcoin’s security rests on elliptic curve digital signature algorithms. When you spend bitcoin, your public key is briefly exposed onchain. Under classical computing, reversing that to obtain a private key is infeasible. Quantum computers running Shor’s algorithm can, in principle, do exactly that during the brief window a transaction is broadcast. The Google paper doesn’t merely confirm this theoretically; it quantifies it with a precision that removes comfortable ambiguity.
Nic Carter, co-founder of Coin Metrics and one of the sharpest minds in digital assets, has been sounding this alarm for months. In a series of essays beginning in October 2025, Carter called quantum computing “the biggest long-term risk to bitcoin’s core cryptography” and accused developers of “sleepwalking towards collapse.” He estimates a quantum computer could meaningfully break elliptic curve cryptography as early as 2028. Approximately 6.9 million BTC could be vulnerable at a sufficient quantum scale, including legacy wallets and Taproot outputs, which already represented more than 21% of all bitcoin transactions in 2025.
Bitcoin’s governance problem
One might ask: can’t bitcoin simply upgrade? Yes, in theory. In practice, this is where the risk compounds.
