Contract Suite

The rwaUSD system is modular. Each contract has a narrow responsibility and an explicit permission boundary.

1. Overview diagram

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2. rwaUSD Token (RwaUsdToken)

Type: ERC‑20 (+ EIP‑2612 permit recommended)

Responsibilities

• Maintain rwaUSD balances

• Mint/burn only by authorized core module(s)

Key rules

• mint(to, amount) only callable by Ledger Core

• burn(from, amount) only callable by Ledger Core (or via allowance-based burnFrom gated to core)

Interfaces (Solidity-style)

function mint(address to, uint256 amt) external;
function burn(address from, uint256 amt) external;
function permit(...) external; // optional

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3. Ledger Core (Ledger)

This is the accounting kernel. Keep it small, boring, and difficult to upgrade.

Responsibilities

• Store collateral balances per account/profile

• Store principal per account/profile

• Enforce all solvency checks using prices and parameters

• Mint/burn rwaUSD

• Record protocol revenue and deficits

Key storage

• locked[accountId][profileId] -> uint256

• principal[accountId][profileId] -> uint256

• index[profileId] -> uint256 (fee index)

• totalPrincipal[profileId] -> uint256

• pausedFlags -> bitmask

• badDebt -> uint256 (explicit deficit tally)

External entrypoints (only from authorized modules)

• lock(profile, account, amount)

• unlock(profile, account, amount)

• increasePrincipal(profile, account, delta)

• decreasePrincipal(profile, account, delta)

• applyIndex(profile) (or invoked by Fee Accumulator)

• startUnwind(account) (called by Unwind Engine)

• settleUnwind(account, clearedPrincipal, clearedFees, collateralOut) (called by Auction House)

Important: the Ledger never calls untrusted external contracts. Anything that touches tokens goes through adapters. Anything that moves collateral in liquidation goes through the Auction House.

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4. Account Manager (AccountManager)

User-facing orchestration: creates accounts, manages permissions, bundles operations.

Responsibilities

• Create Collateral Accounts (accountId)

• Operator permissions per account

• Convenience methods: deposit+mint, repay+withdraw, multi-call sequences

Permissions model

• account owner can grant operators

• operators can be scoped:

  • collateral management

  • issuance/repayment

  • withdrawals

  • full control

Recommended interfaces

function openAccount(address owner) external returns (uint256 accountId);
function setOperator(uint256 accountId, address operator, uint256 permissions) external;

function deposit(uint256 accountId, bytes32 profileId, uint256 amount) external;
function withdraw(uint256 accountId, bytes32 profileId, uint256 amount, address to) external;

function mint(uint256 accountId, bytes32 profileId, uint256 amount, address to) external;
function repay(uint256 accountId, bytes32 profileId, uint256 amount, address from) external;

// Convenience
function depositAndMint(...) external;
function repayAndWithdraw(...) external;

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5. Asset Adapters (AssetAdapter per profile)

Each collateral token requires an adapter to normalize token behavior and enforce custody constraints.

Responsibilities

• Pull collateral tokens from user and hold in adapter custody

• Push collateral tokens to user (withdrawals) or Auction House (unwinds)

• Normalize decimals and non-standard ERC‑20 behavior

• Enforce allowlist constraints if token requires eligible holders

Non-negotiables

• No collateral leaves an adapter without a corresponding Ledger state update

• Adapter must be approved holder if upstream token has restrictions

• Adapter must handle tokens with:

  • 6 decimals

  • missing return values

  • fee-on-transfer (ideally disallowed for v1)

Interfaces

function deposit(uint256 accountId, uint256 amount) external;
function withdraw(uint256 accountId, uint256 amount, address to) external;
function seizeToAuction(uint256 accountId, uint256 amount, address auctionHouse) external;

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6. Risk Registry (RiskRegistry)

On-chain parameter store for collateral profiles and global settings.

Per-profile parameters

• safetyFactor (min coverage multiplier)

• haircut (price discount used for solvency checks)

• mintCap (max principal allowed for profile)

• minPosition (dust threshold)

• penaltyFactor (extra charge when unwound)

• auctionConfig (see Auction House section)

• oracleConfig (feed set + guardrails)

• borrowEnabled / collateralEnabled flags

Global parameters

• global issuance cap (optional)

• peg rail limits

• pause flags

Update rules

• all changes via governance timelock

• emergency roles may only tighten risk or pause modules

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7. Fee Accumulator (FeeAccumulator)

Maintains fee indices for profiles.

Model

• Each profile has a per-second growth factor ratePerSecond in RATE precision

• index[p] increases over time

Mechanics

• Lazy update: accrue(profile) updates index based on block.timestamp - lastAccrual[p]

• Mint/repay operations call accrue(profile) before computing new liability

Interfaces

function accrue(bytes32 profileId) external;
function setRate(bytes32 profileId, uint256 ratePerSecond) external; // timelock