This paper from Google Quantum AI and the Ethereum Foundation details the catastrophic risks that cryptographically relevant quantum computers (CRQCs) pose to the global cryptocurrency ecosystem. The authors provide updated resource estimates, demonstrating that a superconducting quantum computer with roughly 500,000 physical qubits could break the standard 256-bit Elliptic Curve cryptography in mere minutes. This capability introduces a "fast-clock" threat where attackers can intercept and forge transactions in real-time, known as on-spend attacks, alongside the more traditional threat to dormant assets.

Beyond Bitcoin, the analysis identifies systemic vulnerabilities in Ethereum’s smart contracts, Proof-of-Stake consensus, and tokenized real-world assets, which could lead to total network destabilization. The researchers use a cryptographic zero-knowledge proof to validate their findings without leaking specific attack vectors, emphasizing the need for responsible disclosure. Ultimately, the text serves as an urgent call for the blockchain community to migrate to Post-Quantum Cryptography (PQC) and for policymakers to develop "digital salvage" frameworks for recovering at-risk assets. Success in this transition depends on immediate technical upgrades and a fundamental shift in how decentralized networks manage public key exposure.