Bitcoin Signer Error: Witness Program Hash Mismatch

As a Bitcoin developer, you’ve likely encountered issues when attempting to sign transactions using private keys on your local machine. One common error that can occur is the “Witness program hash mismatch” issue, which prevents your script from validating and signing transactions correctly.

In this article, we’ll delve into the details of the problem and provide a step-by-step guide on how to resolve it.

The Issue

When attempting to sign a raw transaction with your private key on Bitcoin Core (BTC-Testnet) using Regtest, you may encounter the following error:

Witness program hash mismatch

This error typically occurs when the script is unable to verify that the witness program hash matches the expected value in the transaction. This can be caused by various factors, such as:

• Incorrect or missing script hashes

• Inadequate private key setup

• Invalid or corrupted transactions

• Scripting errors or syntax issues

Debugging Steps

To troubleshoot this issue and resolve the Witness program hash mismatch error, follow these steps:

1. Verify Private Key Setup

Ensure that your private key is correctly set up in Bitcoin Core. Here are a few things to check:

• Make sure you have installed the bitcoin-qt package and verified its installation.

• Check if your private key file (usually located at $HOME/.Bitcoin/ privkey.json) contains valid script hashes for all scripts, including the transaction you’re trying to sign.

2. Inspect Transaction Details

Gather more information about the transaction you’re attempting to sign:

• Transaction details: Verify that the transaction hash is correct and matches the expected value.

• Script debugging: Run your script with --debug flag to get detailed output, which may help identify any issues.

Example command:

bitcoin-qt --regtest -txindex --debug -o myscript tx 

3. Check Witness Program Hashes

Verify that the witness program hashes for all scripts in your script are correct:

• Get script hashes: Run bitcoin-qt --list-scripts to display all scripts with their corresponding hash.

• Check script hashes: Verify that each script’s script hash matches the expected value.

Example command:

bitcoin-qt --regtest -txindex --debug -o myscript tx 

4. Run Script with Debugging Output

Run your script using --debug flag to generate detailed debugging output:

* bitcoin-qt –regtest -txindex –debug -o myscript tx

This will display a detailed list of transactions, including their hashes and the scripts used.

5. Update Script (Optional)

If you suspect that the script itself is incorrect or outdated, update your script to ensure it matches the latest version available:

• Update script: Rungit pull` or use a package manager like pip to update your script to the latest version.

Example:

git clone 

cd scripthash

git checkout 

6. Re-run Script with Corrected Script Hashes

Once you’ve corrected any issues in the script hashes, re-run your script to verify that it produces correct transaction output.

Conclusion

In this article, we walked through the steps to resolve the “Witness program hash mismatch” error in Bitcoin Core when signing transactions using private keys. By verifying your private key setup, inspecting transaction details, checking witness program hashes, running scripts with debugging output, updating scripts (if necessary), and re-running scripts with correct script hashes, you should be able to overcome this issue and successfully sign raw transactions using Regtest.