> ## Documentation Index
> Fetch the complete documentation index at: https://docs.utexo.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Signing an Intent for Tron

> Build and sign the Permit2 typed-data approval for a Tron source chain with TronWeb.

Permit2 on Tron lets the user lock tokens and produce a signature that authorizes the swap. Tokens remain secure until the resolver executes the swap, on Tron or across chains, using the signature to move funds into escrow.

The typed data is built exactly as for [EVM](/product-suite/swap/api/intents/approvals/evm#how-the-signature-is-built); on Tron the user signs it with TronWeb.

<Note>
  The user must have granted the Permit2 contract an allowance on the source token first. See [Approve for Permit2](/product-suite/swap/on-chain-helpers/approve-for-permit2).
</Note>

## Example

```ts theme={null}
import { TronWeb } from "tronweb";

const BASE_URL = "https://api-swap.utexo.com/affiliate";
const API_KEY = process.env.UTEXO_SWAP_API_KEY!;
const privateKey = process.env.PRIVATE_KEY!;
const destinationAddress = process.env.DESTINATION_ADDRESS!;

const tronWeb = new TronWeb({ fullHost: "https://api.trongrid.io", privateKey });

async function api<T>(path: string, body?: unknown): Promise<T> {
  const response = await fetch(`${BASE_URL}${path}`, {
    method: body === undefined ? "GET" : "POST",
    headers: { "Content-Type": "application/json", "X-API-Key": API_KEY },
    body: body === undefined ? undefined : JSON.stringify(body),
  });
  const text = await response.text();
  if (!response.ok) throw new Error(`${path} failed: ${response.status} ${text}`);
  return (text ? JSON.parse(text) : undefined) as T;
}

const userAddress = tronWeb.address.fromPrivateKey(privateKey);
if (!userAddress) throw new Error("The private key does not produce a valid Tron address");

// 1. Quote: USDT on Tron -> WETH on Ethereum
const quote = await api<any>("/v1/quotes/best", {
  source_chain: 2,
  source_token: "TR7NHqjeKQxGTCi8q8ZY4pL8otSzgjLj6t",
  dest_chain: 1,
  dest_token: "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2",
  amount: 2,
  slippage_bps: "50",
  swap_type: "standard",
  deposit_type: "escrowed",
  retail_user_id: null,
  user_meta: null,
  affiliate_fees: null,
});

// 2. Intent
const intent = await api<any>("/v1/intents", {
  quote_id: quote.id,
  user_source_address: userAddress,
  user_destination_address: destinationAddress,
  refund_address: userAddress,
  user_source_public_key: null,
});

// 3. Build the Permit2 typed data (same rules as EVM)
const params = intent.params_to_sign;
const data = params.additional_data;
const toDecimal = (hex?: string) => (hex ? BigInt(hex).toString() : undefined);

const domain = {
  name: data.domain.name,
  chainId: data.domain.chainId,
  verifyingContract: data.domain.verifyingContract,
};
const message = {
  permitted: { token: quote.source_token, amount: quote.source_amount_lots },
  spender: params.escrow_contract_address,
  nonce: params.nonce,
  deadline: intent.deadline_secs,
  witness: {
    ...data.witness,
    ...(data.witness.minAmountOut ? { minAmountOut: toDecimal(data.witness.minAmountOut) } : {}),
    ...(data.witness.maxAmountOut ? { maxAmountOut: toDecimal(data.witness.maxAmountOut) } : {}),
    ...(data.witness.deadline ? { deadline: toDecimal(data.witness.deadline) } : {}),
  },
};

const signature = tronWeb.trx.signTypedData(domain, data.types, message, privateKey);

// 4. Approval
await api(`/v1/intents/${intent.intent_id}/approvals`, {
  type: "permit2",
  signed_data: signature,
});
```