getUserNonce - Palindrome Crypto Pay SDK Documentation

async getUserNonce(escrowId: bigint, signer: Address): Promise<bigint>

Queries the contract's nonce bitmap and returns the first unused nonce for a specific escrow and signer combination. This is the recommended way to get a nonce for signed transactions.

Nonces prevent replay attacks — each signature can only be used once.

Parameters

escrowId: bigint – The escrow ID
signer: Address – The signer's wallet address

Returns

Promise<bigint> – The next available nonce

import { createPalindromeSDK } from '@/lib/createSDK';

const { sdk, walletClient } = await connectAndInitSDK();

const escrowId = 42n;
const userAddress = walletClient.account.address;

// Get next available nonce
const nonce = await sdk.getUserNonce(escrowId, userAddress);
console.log("Next nonce:", nonce); // 0n, 1n, 2n, etc.

// Use in signature
const deadline = await sdk.createSignatureDeadline(60);
const signature = await sdk.signConfirmDelivery(
  walletClient,
  escrowId,
  deadline,
  nonce  // Use the nonce here
);

How Nonces Work

The contract uses a bitmap to track used nonces efficiently:

Each escrow + signer pair has its own nonce space
Nonces don't need to be sequential (bitmap allows gaps)
Up to 25,600 nonces per escrow per signer (100 words × 256 bits)

// Nonce 0 used → bitmap: 0b0001
// Nonce 2 used → bitmap: 0b0101
// Nonce 1 still available!

Checking Specific Nonce

// Check if a specific nonce is already used
const isUsed = await sdk.isNonceUsed(escrowId, signer, 5n);
console.log("Nonce 5 used:", isUsed);

Batch Operations

// Get multiple nonces at once for batch signing
const nonces = await sdk.getMultipleNonces(escrowId, signer, 5);
console.log("Available nonces:", nonces); // [0n, 1n, 2n, 3n, 4n]

Error Handling

try {
  const nonce = await sdk.getUserNonce(escrowId, signer);
} catch (error: any) {
  if (error.message.includes("Nonce space exhausted")) {
    // Very rare — user has used 25,600+ nonces for this escrow
    console.error("Too many nonces used");
  }
}

See also → isNonceUsed() · getMultipleNonces() · getNonceBitmap()