> For the complete documentation index, see [llms.txt](https://docs.trystable.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.trystable.co/research/usdx-whitepaper/abstract.md).

# Abstract

## Abstract

Stablecoins now move tens of trillions of dollars in annualized onchain transaction volume, with a combined market capitalization of approximately $322 billion as of May 2026. Yet the assets backing them remain narrowly concentrated in short-duration U.S. Treasuries and cash. This reserve composition mirrors the posture of money market funds, not the composition of a durable monetary system. The U.S. dollar, in its institutional form, is supported by a much broader asset base — and the largest single component of that base is not Treasuries but real estate debt. U.S. residential mortgage debt outstanding stands at approximately $13.2 trillion — a sum equal to well over half the entire $22.6 trillion U.S. M2 money supply — with the substantial majority securitized in agency mortgage-backed securities (MBS) and traded in one of the deepest fixed-income markets in the world. So central is this asset class to the dollar that the Federal Reserve itself holds roughly $2.2 trillion of agency MBS on its own balance sheet. It underwrites a substantial fraction of the money supply through bank credit and Federal Reserve operations.

USDX is a USD-pegged stablecoin backed by a portfolio of U.S. residential mortgages and agency MBS. It brings the most-trusted collateral class in American finance onchain, giving any wallet access to the cashflows that have underwritten the American dollar for a century. Holders can stake USDX for mUSDX, a yield-bearing token that accrues the return of the underlying mortgage portfolio net of protocol fees. Peg integrity is maintained by direct redemption against reserves, repo lines against agency MBS for additional liquidity, and a decentralized arbitrage surface across liquidity pools. A separate token, RATES, serves two functions: validators stake RATES to verify loan data and property attestations that gate the minting of new USDX collateral, and RATES stakers provide a first-loss safety module against collateral shortfalls, creating a structural buffer between protocol risk and stablecoin holders.

This paper specifies the collateral framework, mint and redeem mechanics, yield distribution, peg stability apparatus, loss waterfall, technical architecture, and token system of USDX. USDX sources mortgage collateral both from secondary markets and from a native onchain origination channel, allowing the reserve to grow with newly originated loans rather than only through secondary purchases. That $13.2 trillion of debt is secured against roughly $50 trillion of U.S. residential real estate, leaving on the order of $34 trillion in untapped home equity — economically real wealth that today is largely inaccessible without selling or refinancing — and USDX is designed to bring this collateral base onchain. USDX is designed as infrastructure: a dollar backed by the same asset class that underwrites the institutional dollar, composable as a digital asset, and redeemable, auditable, and productive by construction.

**Keywords:** stablecoin, mortgage-backed securities, tokenized real estate, peg stability, collateralized debt, safety module, onchain finance.