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

# AA34: Paymaster Signature Validation Failure

> Resolving paymaster signature rejection issues

<Note>
  The paymaster contract address is specified in the first 20 bytes of `paymasterAndData`.
</Note>

The paymaster's `validatePaymasterUserOp` function has rejected the user operation's signature.

## Resolution Checklist

1. For Custom Paymaster Contracts:
   * Verify correct signing of the user operation
   * Ensure proper encoding of the paymaster signature in `paymasterAndData`
   * Confirm correct computation of the custom operation hash
   * Review the signature verification logic in your paymaster

2. For Third-Party Paymaster Services (e.g., JiffyLabs):
   * Avoid modifying user operation fields after paymaster signing (except `signature`)
   * If unmodified but still encountering errors, [contact their support](https://t.me/JiffyScan)

3. Advanced Troubleshooting:
   * Employ [Tenderly](https://tenderly.co/) or similar tools to investigate `validatePaymasterUserOp` behavior