ar.ca: Designing the Interest-Bearing Digital Dollar

In 2019-2020, stablecoins were mostly pegged to the dollar and parked in wallets collecting nothing. DeFi had begun to generate yield, but only through complex, often risky protocols. For most holders, crypto assets sat dormant — useful for speculation or transfers but inert as a store of value.

Arca Labs asked a different question: What if the digital dollar paid interest?

The instrument they designed — ar.ca — was a registered digital security that held US Treasury securities and passed the yield directly to token holders. The economics of a money market fund. The portability of a blockchain token. The regulatory clarity of a registered security.

We worked with Arca Labs as technical architects and launch infrastructure partners on the design and deployment of the system.

The Regulatory-First Design

Most DeFi projects in 2019-2020 avoided regulatory frameworks as a constraint. Arca Labs did the opposite: they treated registration as a feature. An interest-bearing token that was also a registered security was something institutional investors could hold, custodians could service, and advisors could recommend without compliance violations.

This was the insight that made ar.ca different from algorithmic stablecoins and synthetic yield products. The backing was real — US Treasuries. The registration was real — SEC review, EDGAR filing, prospectus disclosure. The yield was real — not generated by protocol mechanics but by the actual return on government bonds.

For retail holders, this meant yield on stable savings without smart contract risk. For institutions, it meant a digital fixed-income instrument that fit within existing risk frameworks.

Technical Architecture

The token system needed to reconcile two different operational requirements:

On-chain properties: transferability, composability with DeFi protocols, self-custody, 24/7 availability.

Off-chain requirements: NAV calculation, yield accrual, dividend distribution, KYC/AML, regulatory reporting, and the legal wrapper of a registered fund.

The architecture we helped design used a transfer agent model — the on-chain tokens were records of beneficial ownership in the fund, with transfer restrictions enforced at the contract level based on whitelisted addresses (verified investors). Yield accrued daily at the fund level and rebased token supply to distribute returns.

This was different from how most DeFi tokens worked. ar.ca tokens weren't just claims on collateral; they were ownership interests in a regulated fund structure with all the legal protections that entailed.

The Broader Implication

The work on ar.ca influenced how Hanzo thought about the intersection of traditional finance and blockchain infrastructure. The primitive we were helping build — programmable, interest-bearing, regulatory-compliant digital assets — was a building block for a financial system where capital was more accessible and portable than in the current account-and-wire-transfer model.

This fed directly into the design thinking behind Hanzo MPC (multi-party computation for institutional key management), Hanzo Vault (tokenized asset custody), and ultimately the Lux network's approach to financial primitives on programmable infrastructure.

The interest-bearing stablecoin that Arca Labs pioneered in 2019-2020 has since become a mainstream DeFi primitive. We helped build the first serious attempt at doing it right — with real backing, real regulation, and real yield.

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Arca Labs ar.ca was one of the first SEC-registered digital securities with interest-bearing mechanics. The infrastructure lessons from that work informed Hanzo's subsequent financial infrastructure products.