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

The Ethereum network uses a unique algorithm to create and validate transactions (Tx). An 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 Ethereum hashes, focusing specifically on Tx hashes.

What are hashes?

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

Calculating Hashes in Ethereum: A High-Level Overview

To calculate Ethereum hashes, 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 input Tx data (including all variables). This is done using the eth account command:

eth account  --send-receipt

This will create a new transaction with 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 Tx.

Fields for double SHA hash

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

  • From: The address that initiated the transaction.
  • To: The address receiving the funds (if applicable).
  • Amount: The amount being transferred (optional).
  • GasPrice: The gas price for the transaction (optional).
  • GasLimit: The maximum allowed gas limit for the transaction (optional).

Field Order

Ethereum: How to calculate a hash of a Tx?

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

Sample Transaction

Here is an example Tx:

{
"from": "0x1234567890abcdef",
"to": "0x9876543210fedcba",
"value": 10,
"gasPrice": 20000,
"gasLimit": 300,000,
"nonce": 0,
"blocknumber": 1000
}

Double SHA-256 hash calculation

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

{
"from": "0x1234567890abcdef",
"to": "0x9876543210fedcba"
}

The result will be new transaction with the same hash value.

Final hash calculation

Combining the previous two hashes, we get:

eth hash --tx_hash = `1234567890abcdef@1234a5b6c7d8e9f0g0h1i2j3k4l5m6n7p8q9r10t11u12v13w14x15y16z17ab18cd**

This is the final Tx hash.

Conclusion

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