Chillar Stablecoin

An experimental ETH-backed stablecoin system with a depositor-funded collateral buffer. Users mint and burn STC against ETH at a price provided by an on-chain Oracle, while liquidity providers deposit ETH to absorb deficits and earn fee-backed upside through DPC (DepositorCoin).

What this is

• Stablecoin core: STC is minted by sending ETH, and burned to redeem ETH at the Oracle price.
• Collateral buffer: depositors add ETH to cover deficits and receive DPC representing a claim on the surplus.
• Fee flow: mint and burn fees stay in the contract and increase surplus for DPC holders.
• Manual Oracle: price is updated by an owner address (intended for testing / prototyping).

Contracts

• contracts/StableCoin.sol — STC mint/burn logic, fee accounting, collateral buffer entry/exit.
• contracts/DepositorCoin.sol — DPC ERC20 minted/burned by StableCoin as the buffer share token.
• contracts/Oracle.sol — owner-updated ETH price feed.
• contracts/WadLib.sol — 18-decimal fixed-point math helpers.
• contracts/ERC20.sol — a minimal Chillar ERC20 token contract (not used by StableCoin).

System flow

Mint STC

1. User sends ETH to StableCoin.mint().
2. If there are existing depositors, a fee (percentage of ETH) is retained in the contract.
3. STC minted equals msg.value * oraclePrice (in USD units; see decimals note below).

Burn STC

1. User calls StableCoin.burn(amount).
2. Contract verifies there is no deficit.
3. User receives ETH based on amount / oraclePrice, minus a fee if depositors exist.

Deposit collateral buffer

• depositCollateralBuffer() is used to cover a deficit and establish (or grow) surplus.
• On first recapitalization, a 10% initial collateral ratio is enforced and a new DPC token is deployed.
• Subsequent deposits mint DPC proportional to current surplus.

Withdraw collateral buffer

• withdrawCollateralBuffer() burns DPC and returns ETH based on the depositor share of surplus.

Units and decimals

• WadLib and token supplies assume 18 decimals.
• The Oracle price should be provided in the same 18-decimal USD-per-ETH units to keep calculations consistent (e.g., $1,500 = 1500e18).

Local development

Requirements

• Node.js (LTS recommended)
• npm

Install

npm install

Compile

npx hardhat compile

Start a local chain

npx hardhat node

Deployment (example flow)

The repo includes a sample deploy script, but it does not yet wire the StableCoin system. A typical local flow:

1. Deploy Oracle.
2. Set the ETH price on the Oracle.
3. Deploy StableCoin with the Oracle address and a fee percentage.
4. Interact via Hardhat console or a custom script.

Example (Hardhat console):

npx hardhat console --network localhost

const Oracle = await ethers.getContractFactory("Oracle");
const oracle = await Oracle.deploy();
await oracle.deployed();
await oracle.setPrice(1500n * 10n ** 18n); // $1,500 with 18 decimals

const StableCoin = await ethers.getContractFactory("StableCoin");
const stc = await StableCoin.deploy(1, oracle.address); // 1% fee
await stc.deployed();

// Mint 1 ETH worth of STC
await stc.mint({ value: ethers.utils.parseEther("1") });

Project layout

• contracts/ — Solidity contracts.
• scripts/ — deployment scripts (currently a sample).
• test/ — tests (currently the Hardhat default sample).

Status and notes

• Tests and deploy script are placeholders from the Hardhat template and need to be updated for StableCoin.
• The system is experimental and not audited. Do not use in production or with real funds.

License

ISC (see package.json).