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Multi-Token Pricing

PAY.ID supports USD-equivalent pricing across multiple tokens, allowing rules to check payment values in USD regardless of the token used.

Overview​

Instead of checking raw token amounts (which vary by token decimals), you can now check the USD equivalent of any payment. This enables:

  • USD-based spending limits - e.g., "Max $35 per payment" regardless of whether it's USDC, USDT, or ETH
  • Multi-token minimum thresholds - e.g., "Minimum $10 payment" across all supported tokens
  • Cross-token daily limits - e.g., "Daily limit of $1000 across all tokens"

Supported Tokens​

Currently supported via Chainlink Price Feeds:

  • USDC/USD - Circle USD Coin
  • USDT/USD - Tether USD
  • DAI/USD - MakerDAO
  • WBTC/USD - Wrapped Bitcoin
  • LINK/USD - Chainlink
  • UNI/USD - Uniswap
  • ETH/USD - Native Ethereum

How It Works (Hybrid Approach)​

PAY.ID uses a hybrid off-chain + on-chain model for USD value rules:

  1. Off-chain: SDK fetches Chainlink price → computes oracle.txValueUsd → WASM rule engine evaluates
  2. On-chain: PayWithPayID.payERC20WithOracleGuard spot-checks the same math as defense-in-depth

1. Token Price Oracles​

PAY.ID uses Chainlink Price Feeds to get real-time token prices in USD:

import { TOKEN_PRICE_ORACLES } from '@/constants/oracles';

const usdcPriceOracle = TOKEN_PRICE_ORACLES[chainId]['USDC/USD'];
const usdtPriceOracle = TOKEN_PRICE_ORACLES[chainId]['USDT/USD'];

2. USD Equivalent Calculation​

The USD equivalent is calculated using the formula:

txValueUsd = (tokenAmount × tokenPrice) / (10^tokenDecimals × 10^8)

Where:

  • tokenAmount: Raw token amount in token units
  • tokenPrice: Token price in USD (8 decimals, Chainlink standard)
  • tokenDecimals: Token decimals (e.g., 6 for USDC, 18 for ETH)

SDK helper:

import { computeTxValueUsd } from 'payid';

const txValueUsd = computeTxValueUsd(amount, decimals, priceInUsd); // 8-decimal USD

3. Context Extension​

The computed value is injected into the oracle namespace before rule evaluation:

interface OracleContext {
  txValueUsd: string;        // USD equivalent (8 decimals)
  txValueUsdFormatted: string; // e.g. "$45.00"
  tokenPrice: string;          // Raw oracle price
}

Usage Examples​

Example 1: USD-Based Spending Limit​

Create a rule that limits payments to $35 USD regardless of token:

{
  "if": {
    "field": "oracle.txValueUsd",
    "op": "<=",
    "value": 3500000000
  },
  "message": "Payment exceeds $35 USD limit"
}

What this means:

  • 35 USDC = $35 USD ✅
  • 0.01 ETH (at $3500) = $35 USD ✅
  • 35 USDT = $35 USD ✅
  • 100 USDC = $100 USD ❌ (rejected)

Example 2: Multi-Token Minimum Threshold​

Require minimum $10 USD payment:

{
  "if": {
    "field": "oracle.txValueUsd",
    "op": ">=",
    "value": 1000000000
  },
  "message": "Payment below $10 USD minimum"
}

Example 3: Cross-Token $45 Minimum​

The classic "send any token but min $45" rule:

{
  "id": "cross_token_min_45",
  "if": {
    "field": "oracle.txValueUsd",
    "op": ">=",
    "value": 4500000000
  },
  "message": "Min $45 required. You sent ${oracle.txValueUsd|div:100000000} USD-worth of {tx.asset}"
}

Frontend Integration (usePayIDFlow)​

usePayIDFlow automatically injects oracle.txValueUsd when you pass tokenPriceOracle and tokenDecimals:

import { usePayIDFlow } from 'payid-react';

const { execute } = usePayIDFlow();

await execute({
  receiver: '0xReceiver...',
  asset: '0xUSDC...',
  amount: 50_000_000n, // 50 USDC (6 decimals)
  payId: 'pay.id/alice',
  tokenDecimals: 6,
  tokenPriceOracle: '0x...', // Chainlink USDC/USD feed
  minUsdValue: 45_00000000n, // optional: on-chain guard
});

With Token Config Helper​

import { getTokenConfig, getTokenPriceOracle } from '@/constants/tokens';

const token = getTokenConfig(chainId, 'USDC');
const oracle = getTokenPriceOracle(chainId, 'USDC');

await execute({
  receiver: '0x...',
  asset: token.address,
  amount: parseUnits('50', token.decimals),
  payId: 'pay.id/alice',
  tokenDecimals: token.decimals,
  tokenPriceOracle: oracle,
  minUsdValue: 45_00000000n,
});

On-Chain Oracle Guard​

For defense-in-depth, PayWithPayID includes payERC20WithOracleGuard:

function payERC20WithOracleGuard(
  Decision calldata d,
  bytes calldata sig,
  bytes32[] calldata attestationUIDs,
  address tokenPriceOracle,
  uint256 minUsdValue,   // 8 decimals
  uint8 tokenDecimals
) external;

If tokenPriceOracle is set and minUsdValue > 0, the contract:

  1. Queries Chainlink latestRoundData
  2. Computes usdValue = (amount * price) / 10^(decimals + 8)
  3. Reverts with BELOW_USD_MINIMUM if under threshold

SDK Helpers​

import { computeTxValueUsd, formatUsdValue } from 'payid';

const usdValue = computeTxValueUsd(
  1_000_000n,    // 1 USDC
  6,             // USDC decimals
  100_000_000n   // $1.00 price (8 decimals)
); // → 100_000_000n ($1.00)

formatUsdValue(usdValue); // "$1.00"

Oracle Addresses​

Oracle addresses are configured per chain in @/constants/oracles.ts:

export const TOKEN_PRICE_ORACLES: Record<number, Record<string, `0x${string}`>> = {
  1: {
    'USDC/USD': '0x8fFfF9545Ff14a92c8329c339F71d3f3Ea8eD444', // Mainnet
    'USDT/USD': '0x3E7d1eAB13ad0104d2750B8863b489D65364e32D', // Mainnet
    'DAI/USD': '0xAed0c38402a5d19df6E4c03f4322c2963490d050', // Mainnet
    'WBTC/USD': '0xF4030086522a5bEEa4988F8cA5B36dbC97BeE88c', // Mainnet
    'LINK/USD': '0x2c1d072e956AFFc0D435Cb7D389FaE8fC5B9cB2D', // Mainnet
    'UNI/USD': '0xD71eCFF9422D8057F9692e8DdA2B7549aCf96663', // Mainnet
  },
  11155111: {
    'USDC/USD': '0xA2F78d2358df4E29c589B9C1Ada1ddc062c1Ec4e', // Sepolia
    'USDT/USD': '0x20955D69f13E1e2c3c1f9BfF2Ad5C807485A4f0e', // Sepolia
    'DAI/USD': '0x14866185B1962A69b940F2c2953A6C3747525b43', // Sepolia
    'WBTC/USD': '0x7e87009ceF4D986fC2719BfF2adEA5565dfB9C56', // Sepolia
    'LINK/USD': '0xc59E36313BAa28Cf64E2863425DCc5b33Ae4C8f3', // Sepolia
    'UNI/USD': '0xD71eCFF9422D8057F9692e8DdA2B7549aCf96663', // Sepolia
  },
  31337: {
    'USDC/USD': '0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419', // Mock for local dev
    'USDT/USD': '0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419', // Mock for local dev
    'DAI/USD': '0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419', // Mock for local dev
    'WBTC/USD': '0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419', // Mock for local dev
    'LINK/USD': '0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419', // Mock for local dev
    'UNI/USD': '0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419', // Mock for local dev
  },
};

Notes​

  • USD values are stored with 8 decimals (Chainlink standard)
  • Rule engine uses oracle.txValueUsd (not tx.amountUsd)
  • usePayIDFlow auto-injects oracle context when tokenPriceOracle is provided
  • On-chain guard (payERC20WithOracleGuard) requires contract redeployment
  • Fallback to mock addresses on localhost for development