Bitcoin: Witness Program Hash Mismatch Error When Sending a Signed Transaction on Regtest

Bitcoin: Hash mismatch error when sending signed transaction in Regtest

As a Bitcoin developer, you are probably familiar with the nuances of running a test node or testing your own wallet. However, when it comes to sending transactions, even simple operations can cause unexpected errors. In this article, we will delve into a specific error that is frustrating many users and explore why it occurs.

Error: Witness Program Hash Mismatch

When you try to submit a transaction on your Bitcoin regtest node (also known as a “mock” or “testnet” node), the error message you see is very informative:

Status Err("RPC Error: Object {\"code\": Number (-26), \"message\": Invalid hash for witness program"

At first glance, this appears to be an error related to the transaction itself. However, upon closer inspection, we can see that the real problem lies in the witness program.

Witness Program: Cryptographic Hash Scheme

In Bitcoin, transactions are represented as a sequence of blocks with various elements such as inputs, outputs, and transactions. To secure these transactions, each block is linked to its predecessor via a Mordell-Samuel curve, a cryptographic hash function that helps verify the chain of ownership.

The program The witness is responsible for generating this cryptographic hash, which is needed to ensure the integrity of the blockchain. It is essentially a complex mathematical formula that takes into account various parameters such as the block number, the Merkle root, and the witness data (e.g., the input indices and outputs of the transactions).

Hash Mismatch Error: What Goes Wrong

When submitting transactions on a regtest node, you are probably using the regtest command-line tool to submit the transaction. However, in some cases, this process can lead to a hash mismatch error.

Here is what happens:

• Witness Hash Calculation: When you run a transaction on a regtest node, the witness program is used to generate a cryptographic hash for each block.

• Transaction Verification: You then verify that the transaction has been properly verified using tools like bfs (Bitcoin Fork Checker) or bfs-checker.

• Hash Calculation: Before sending a transaction to the network, you calculate the hash of the witness program using a tool like witnessprogramhash.

Problem: Invalid witness program hash

In some cases, there may be a problem with calculating the witness program hash. This can happen for various reasons, such as:

• Invalid inputs (e.g. invalid input indices or transaction outputs).

• Outdated witness program versions.

• Network connectivity issues.

When a regtest node encounters a hash mismatch error, it is usually caused by one of the following factors. In this case, the regtest tool will display an error message that the witness program hash is invalid.

Solution: Debugging and Troubleshooting

To resolve this issue, follow these steps:

• Check the inputs: Make sure that all inputs are correct and valid.

• Update Witness

  : Check for any updates to the Witness code or version.

• Run witnessprogramhash

  : Use a tool like witnessprogramhash with valid input to regenerate the Witness hash.

If none of these steps resolve the issue, you may need to seek further assistance from the Bitcoin community or a testnet node administrator.

Application

The Witness hash mismatch error is a common issue that can be caused by a variety of factors. Understanding the root causes and taking corrective action should allow you to resolve this error and successfully submit transactions to the regtest node. Be sure to check your inputs, update your Witness version, and restart witnessprogramhash with the correct inputs to ensure your transaction goes through smoothly.

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