Verifying Signature in a P2WPKH Transaction: A Step-by-Step Guide

Cryptocurrencies like Bitcoin have gained immense popularity over the years, and one of the most significant security features that contribute to their trustworthiness is the verification process for signature transactions. In this article, we will delve into how to verify signatures in a P2WPKH (Private Transaction) transaction on Bitcoin.

Standard P2PKH Signature Verification Process

For standard P2PKH transactions, the signature verification process involves the following steps:

• NewTransaction: The transaction is created and includes the sender’s address, recipient’s address, amount, and other relevant details.

• Settle the TxOuts well: The transaction outputs are settled (i.e., their balances are updated) to ensure that there are sufficient funds for the transaction.

• Set all TxIn scripts to empty: All transaction inputs are set to an empty script hash, indicating that no funds or assets will be transferred from the sender’s wallet to the recipient’s address.

• Insert the Previous Locking information: The transaction includes a “Previous Locking” field, which contains the previous locking script (e.g., the sender’s public key) and any associated data.

Generating Signature Digest

To verify the signature in a P2WPKH transaction, we need to generate the signature digest. Here’s how:

• Create a new Transaction object: A new NewTransaction object is created, which includes all the necessary details.

• Settle the TxOuts well: The outputs are settled according to the specified rules.

• Set all TxIn scripts to empty: All transaction inputs are set to an empty script hash.

• Insert the Previous Locking information: The previous locking data is inserted into the transaction.

Signature Digest Generation

The signature digest is generated using a cryptographic hash function (e.g., SHA-256). The resulting hexadecimal string is used to verify the signature in subsequent transactions.

Here’s an example of how to generate the signature digest:

import hashlib


tx_outs = {"amount": 10.0, "scriptPubKey": "q1..."}

tx_in_scripts = {}


previous_locking = {"public_key": "sender_public_key"}


new_transaction = NewTransaction(tx_outs=tx_outs,

                              tx_in_scripts=tx_in_scripts,

                              previous_locking=previous_locking)



Generate signature digest using SHA-256

signature_digest = hashlib.sha256(new_transaction.signature).hexdigest()

Verify Signature in a P2WPKH Transaction

To verify the signature in a P2WPKH transaction, you need to follow these steps:

• Get the signed data: The recipient of the transaction needs to obtain the signed data, which includes the transaction ID and other relevant information.

• Create a new Transaction object: A new NewTransaction object is created, including all the necessary details.

• Settle the TxOuts well: The outputs are settled according to the specified rules.

• Set all TxIn scripts to empty: All transaction inputs are set to an empty script hash.

• Insert the Previous Locking information: The previous locking data is inserted into the transaction.

Verify Signature in a P2WPKH Transaction

Here’s how to verify the signature in a P2WPKH transaction:

“`python

import hashlib

signed_data = …

tx_outs = {“amount”: 10.0, “scriptPubKey”: signed_data}

tx_in_scripts = {}

previous_locking = {}

new_transaction = NewTransaction(tx_outs=tx_outs,

tx_in_scripts=tx_in_scripts,

previous_locking=previous_locking)

Generate signature digest using SHA-256

signature_digest = hashlib.sha256(new_transaction.signature).

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