Bitcoin: The $145 billion math — quantum risk large but manageable

Google Quantum AI’s March 2026 whitepaper updated resource estimates for quantum attacks on elliptic-curve signatures used by Bitcoin and other chains, highlighting that older Pay-to-Public-Key (P2PK) scripts secure roughly 1.7 million BTC that are exposed to “at-rest” quantum attacks. The paper explains why certain attack variants could be executed with far fewer qubits than earlier estimates.

Technically, the authors present two circuit variants requiring about 1,200–1,450 logical qubits and tens of millions of Toffoli gates; on superconducting architectures these map to fewer than half a million physical qubits and could enable attacks within minutes in specific models. The report distinguishes between at-rest and on-spend vectors and stresses that while some address types remain relatively safe until spent, transactions that reveal public keys create brief but critical vulnerability windows.

Financially, the implication received broad coverage: aggregates of vulnerable coins have been translated by commentators into large dollar figures (the “$145 billion” framing has circulated for headline impact), but such estimates depend directly on BTC market price and which subset of addresses is counted. Google’s paper itself frames the exposed dormant supply as “tens or hundreds of billions of dollars,” underscoring price sensitivity and uncertainty rather than asserting a single catastrophic number.

Market analysts and major outlets note that the study raises urgency but not immediate collapse; no operational cryptographically relevant quantum computer has been demonstrated that performs these attacks in the wild. The industry reaction has focused on mitigation: accelerating migration to post-quantum cryptography (PQC), implementing private mempools or commit-reveal schemes to blunt on-spend attacks, and custodians redesigning key-management workflows.

In a broader economic and policy context, the findings create complex trade-offs between immutability of blockchain-held property and systemic stability. Policymakers, protocol developers and custodians will need to coordinate — options range from software-level PQC rollouts to legal frameworks for “digital salvage” of abandoned assets. Analysts expect that, provided coordinated technical and regulatory steps proceed, the quantum risk will remain a manageable transition challenge rather than an existential collapse.