Ethereum: How to calculate a hash of a Tx?

Calculating Hashes on Ethereum: A Step-by-Step Guide

The Ethereum network uses a unique algorithm to create and validate transactions (Tx). One essential part of this process is calculating hashes, which are used to verify the integrity and authenticity of each transaction. In this article, we will explore how to calculate hashes on Ethereum, focusing specifically on Tx hashes.

What are hashes?

Hashes are one-way cryptographic functions that take input data (in this case, a Transaction) as an input and produce a fixed-size string output. The hash is unique and unalterable, making it perfect for verifying the authenticity of a transaction.

Calculating Hashes on Ethereum: A High-Level Overview

To calculate hashes on Ethereum, you need to follow these steps:

• Create a Transaction: Start by creating a new Tx using the tx command in the Ethereum CLI:

eth tx create  

Replace with the hash of the transaction you want to calculate.

• Double SHA-256 Hashing: To create a hash, we need to double SHA-256 hash the Tx’s input data (including any variables). This is done using the eth account command:

eth account  --send-receipt

This will create a new transaction with the double-sha256 hashed values.

• Final Hash Calculation: The final hash is created by combining the previous two hashes (Tx and double-sha256 hashed input data). This is done using the eth hash command:

eth hash  --tx_hash 

This will output the final hash of the Tx.

Fields to Double SHA Hash

To create a valid transaction, you need to include the following fields in your Tx:

• From: The address that initiated the transaction.

• To: The address receiving the funds (if applicable).

• Value: The amount being transferred (optional).

• GasPrice: The gas price for the transaction (optional).

• GasLimit: The maximum allowed gas limit for the transaction (optional).

Order of Fields

The order in which you include these fields does not matter. What matters is that they are included in the correct format.

Example Transaction

Here’s an example Tx:

{

  "from": "0x1234567890abcdef",

  "to": "0x9876543210fedcba",

  "value": 10,

  "gasPrice": 20000,

  "gasLimit": 300000,

  "nonce": 0,

  "blockNumber": 1000

}

Double SHA-256 Hash Calculation

Using the eth account command, we can create a double-sha256 hashed input data:

{

  "from": "0x1234567890abcdef",

  "to": "0x9876543210fedcba"

}

The output will be a new transaction with the same hash value.

Final Hash Calculation

Combining the previous two hashes, we get:

eth hash --tx_hash = `1234567890abcdef@1234a5b6c7d8e9f0g0h1i2j3k4l5m6n7p8q9r10t11u184x15b13w1

This is the final hash of the Tx.

Conclusion

Calculating hashes on Ethereum involves creating a transaction, double-sha256 hashing its input data, and then combining these two hashes to create a final hash. By following this process, you can verify the integrity and authenticity of each transaction on the Ethereum network.