Ethereum Transaction Hash Calculation
================================================
Calculating Ethereum transaction hashes can be a bit tricky, especially for those new to Ethereum. In this article, we will explore how Ethereum calculates transaction hashes and provide examples to help you understand the process.
Understanding Ethereum Transactions
———————————–
In Ethereum, each block contains multiple transactions, known as “messages.” Each message is a sequence of entries (called “data”) followed by a signature (known as a “block hash”). The block hash is calculated using a complex algorithm that takes into account previous data and hashes.
Transaction Hash Algorithm
———————————–
The Ethereum transaction hash algorithm is based on the following steps:
- Hash Functions
: Ethereum uses two types of hash functions:
Keccak-256: A 256-bit hash function designed to be computationally fast.
BLAKE2b: A 256-bit hash function designed to be memory-safe and fast.
- Message Normalization
: Each transaction is normalized into an array of bytes, which represents the input data.
- Block Hash: The block hash is calculated by concatenating the hash of the previous block, the message header (a 4-byte signature of the block), and the normalized input data.
Example: Calculating the hash of a single transaction
————————————————-
Let’s assume we have a transaction with the following inputs:
transaction_id: 0x1234567890abcdef
from: 0x9876543210fedcba
to: 0x876543210fedcba
value: 0x1234567890abcdef
The input data would be:
[0x1234567890abcdef, 0x9876543210fedcba, 0x876543210fedcba]
Then, we concatenate the block hash (using “Keccak-256”) with the message header (a signature) and the normalized input data:
block_hash = Keccak-256(0x1234567890abcdef + 0x9876543210fedcba + 0x876543210fedcba)
message_header = 0x67454bbf
normalized_input_data = [0x1234567890abcdef, 0x9876543210fedcba, 0x876543210fedcba]
Next, we concatenate the concatenated block hash with the normalized input data to form the transaction hash:
transaction_hash = Keccak-256(block_hash + message_header + normalized_input_data)
Using a tool or library
——————–
To calculate the transaction hash, you will need a tool or library that supports Ethereum’s hash functions. Some popular options include:
ethhash: A Python library that computes Ethereum hashes.
blockchain(a Node.js library): Provides a convenient API for working with Ethereum data structures.
In summary, Ethereum computes transaction hashes by concatenating the hash of the previous block, the message header (a signature), and the normalized input data. The resulting hash is then computed using two hash functions: Keccak-256 and BLAKE2b. By following these steps, and using a tool or library to help you, you should be able to compute the hash of any Ethereum transaction.
Please note that this is only an introduction to the process. For more advanced topics such as smart contracts and blockchain programming, please refer to the official resources and documentation from the Ethereum developers.
