The Asymmetric Attack Surface of Fiat Substitutes: A Measurement Framework and Owner-Bound Offline Custody Architecture

USDC and USDT can alter theft risk through remote reach, reusable exploit logic, rapid transfer, and common-mode compromise. This methodological feasibility study distinguishes attack topology from realized loss and defines exposure-normalized gross and net loss intensities under explicit comparability conditions.Public evidence does not identify a global per-dollar theft probability or a defensible cross-domain deterrence ratio. As an illustrative reported-loss calibration, 2019 Federal Bureau of Investigation data record USD 1.424 billion in reported stolen currency and USD 36.981 million recovered; relative to USD 1.7598 trillion of U.S. currency in circulation at year-end, gross reported loss intensity is 0.0809% and the recovery share is 2.60%. Binance breach reports estimate approximately USD 6.30–6.43 billion stolen in October 2026 but provide no matched USDC/USDT loss numerator and exposure denominator. Relative-vulnerability comparisons remain conditional estimands. The study specifies an owner-bound offline custody architecture in which the complete spend key is never printed, independent shares are required, and signing occurs in a verified offline environment. A framework linking attacker incentives to net loss and a control-level comparison identify conditional benefits, transferred attack paths, and residual risks without claiming empirically demonstrated superiority.