Ethereum: What is the script assembly and execution in P2TR spend (spend from Taproot)

Ethereum: Understanding Compiling and Executing Scripts for P2TR Spending (Taproot Spending)

Now that you have a good understanding of writing and executing a Bitcoin script, especially in relation to Taproot (P2PKH) payments, we will dive deeper into the specifics of writing a script for P2TR spending (Taproot spending).

What is P2TR Spending?

P2TR spending involves spending Bitcoin from a public address that was previously spent using Taproot (P2PKH). In other words, you are re-spending the same Bitcoin that was originally spent in the underlying transaction. This allows for more complex and secure payments without having to create new scripts or mine new addresses.

P2TR Script Assembly Costs

To perform P2TR spending, we first need to understand the script assembly process used by Ethereum’s Ropsten testnet. The key components of an Ethereum script are:

• Input Scripts: These define how the input amount should be spent.

• Output Scripts: These define what is sent to the recipient and any additional fees or transfers.

For P2TR spending, we have two main input scripts: one for the original Taproot transaction and another that creates a new script for the re-spent bitcoins.

Tapping the Taproot Script

The original taproot transaction has an input script of type scriptPubKey, which is a key-value pair representing the public address to be spent. This input script is used as the first input in our P2TR spend.

0x1... (public address)

Taproot script output

The re-spent Taproot transaction has an output script that specifies how the amount should be sent. The scriptPubKey field of this output script contains the public address to which the re-spent bitcoins are sent.

0x1... (public address)

P2TR script assembly

Now let’s combine these two scripts to create a P2TR spend that re-sends the same Taproot transaction. We will use Solidity, a popular programming language for Ethereum smart contracts, to implement this scheme.

“`force

pragma solidity ^0.8.0;

contract TaprootSpend {

// Insert script from the original master root transaction

to contact the public landlord;

// Function to execute P2TR consumption

function executeP2TR(uint amount) public {

// Create a new input script for re-spent bitcoins

public recipient address;

uint256 public outputAmount = 0;

// Define the output script using the output script of the original taproot transaction

function getOutputScript() internal returns (address, uint256) {

returnAddress(0x1…, owner), amount;

}

// Use the re-spent Taproot transaction to calculate the recipient address and amount

public address newAddress;

uint256 public newAmount = 0;

// Define a function that takes the output script of the original Taproot transaction and calculates the corresponding inputs for the re-spent bitcoins

function getNewInputs() internal returns (address[] memory, uint256[]) {

// Calculate the recipient address using the public address from the original Taproot transaction

address [] memory recipients = newaddress;

// Calculate the output amount in wei

uint256[] memory outputs = newuint256(recipients.