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Introduction

The Stablecoin Stack is an open architecture for processing stablecoin payments on Ethereum-compatible networks. It is built on a single central proposition: that cryptographic signatures are a superior foundation for payment authorisation compared to identity-based delegation models, and that the tooling to make this practical for everyday users is both achievable and urgently needed.

A working prototype exists. This specification series formalises that prototype for production implementation, independent audit, and institutional review. The Foundation does not theorise and then build — it builds, tests, and then specifies. Everything documented here has been demonstrated to work.

What the Stablecoin Stack Is​

The Stablecoin Stack defines a complete, custody-free payment protocol. A payer signs two off-chain authorisations — no blockchain transaction required from them, no gas token needed. A Relayer operated by the Payment Processor submits the transaction on their behalf. A Settlement Contract verifies the signatures, moves the tokens, distributes fees, and registers acquirers — atomically, non-custodially, and in a single on-chain transaction.

The system is designed around three guarantees that are enforced at the contract level, not by policy:

  • The payer's funds cannot be moved without their signature. No operator, no processor, no acquirer can authorise a transfer on the payer's behalf.
  • The administrator cannot touch participant funds. Fee parameters can be adjusted; balances cannot be drained.
  • Every operation either completes entirely or reverts entirely. There is no partial execution.

Who This Is For​

This repository is the authoritative specification source for the Stablecoin Stack. It is written for four distinct audiences, each of whom has a different entry point:

Developers who want to build against the protocol — integrate a wallet, implement a processor, or deploy a Settlement Contract — should start with the core concepts to build a mental model, then use the guides for step-by-step implementation, and consult the formal specification and reference for normative detail.

Institutions evaluating the protocol for adoption, integration, or partnership should read this document, then Why Cryptographic Payments for the design rationale, and System Architecture for component boundaries and trust model.

Auditors assessing cryptographic correctness, security model, or protocol conformance should go directly to the formal specification, paying particular attention to Sections 11 (Security Model) and 12 (Conformance). The normative references list all cited standards.

Regulators reviewing custody model, consumer protection, or systemic risk should read this document and System Architecture, focusing on the trust boundaries and administrative privilege constraints in Section 11.7 of the formal specification.

Scope​

The current specification covers:

  • the on-chain Settlement Contract (permit verification, token transfer, fee distribution, acquirer registration)
  • the payload structures, signing conventions, and submission protocol for the Payment Processor API
  • the system architecture, component responsibilities, and trust model for a fully conformant deployment
  • the acquiring model and fee distribution mechanics
  • the end-to-end payment flow from session creation through settlement confirmation

The following are planned for subsequent specifications and are explicitly out of scope here:

  • Checkout Engine API (merchant-facing session and charge management)
  • Broadcast Layer WebSocket protocol (wallet-to-gateway communication)
  • Individual microservice interface specifications
  • Key management and custody procedures
  • Token issuance and redemption mechanics
  • Regulatory compliance guidance

Status and Contributing​

All content in this repository is in Draft status. The Foundation actively seeks contributors across all profiles — protocol reviewers, implementers, security auditors, and legal and regulatory professionals. See governance/contributing.md for how to participate.