Permit2 SDK for IndexedEx

Comprehensive guide for using Permit2 in the frontend for vault operations.

Quick Start

import { PERMIT2_ADDRESS, SignatureTransfer } from '@uniswap/permit2-sdk'

Two Patterns

1. Signature Transfer (Recommended)

Gasless, no pre-approval needed beyond initial Permit2 allowance.

• Skill: permit2-signature-transfer
• Use for: One-time signatures per swap/deposit/withdraw
• Security: Signature bound to specific action via witness

2. Allowance Transfer

Persistent approvals - user approves once, protocol spends repeatedly.

• Skill: permit2-allowance-transfer
• Use for: Frequent trading, recurring deposits

Exchange Types (Witness Context)

Exchange	Selector	Witness Data
exchangeIn	0x89d61912	tokenIn, tokenOut, vault, amountIn
exchangeOut	0x612d4427	tokenIn, tokenOut, vault, amountOut, maxAmountIn
swapSingleTokenExactOut	(Balancer)	pool, tokenIn, tokenOut, amountOut

Key Topics

• Nonce handling: permit2-nonce-management
• Wagmi integration: permit2-wagmi-integration
• TypeScript types: permit2-types
• Chain addresses: permit2-addresses

Example: Swap with Witness

// Witness binds signature to this exact swap
const witness = {
  actionId: keccak256(encodePacked(
    ['address', 'address', 'address', 'uint256'],
    [tokenIn, tokenOut, vaultAddress, amountIn]
  ))
}

// Get permit data (EIP-712 ready)
const { domain, types, values } = SignatureTransfer.getPermitData(
  permit,           // amount, nonce, deadline
  PERMIT2_ADDRESS,
  chainId,
  { witness, witnessTypeName: 'Witness', witnessType: WITNESS_TYPE }
)

// User signs, then your contract calls Permit2