Calculating an Ethereum Transaction Hash
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Calculating the hash of Ethereum transactions 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
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In Ethereum, each block contains multiple transactions known as “messages.” Each message is a series of inputs (called “data”) followed by a signature (known as a “block hash”). The block hash is calculated using a complex algorithm that takes into account the data and previous hashes.
Transaction Hash Calculation Algorithm
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The Ethereum transaction hash calculation 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 a byte array that represents the input data.
- Block Hash Calculation
: The block hash is calculated by concatenating the previous block hash, the message header (4-byte block signature), and the normalized input data.
Example: Calculating the hash of a single transaction
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Let’s assume we have a transaction with the following inputs:
transaction_id: 0x1234567890abcdef
“from”: “0x9876543210fedcba”.
“to”: “0x876543210fedcba”.
value: 0x1234567890abcdef
The input will be:
“[0x1234567890abcdef, 0x9876543210fedcba, 0x876543210fedcba]”
We then concatenate the block hash (using “Keccak-256”) with the message header (signature) and normalized input:
block_hash = Keccak-256(0x1234567890abcdef + 0x9876543210fedcba + 0x876543210fedcba)
message_header = 0x67454bbf
normalized_input = [0x1234567890abcdef, 0x9876543210fedcba, 0x876543210fedcba]
We then concatenate the hash of the concatenated block 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
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To calculate the transaction hash, you will need a tool or library that supports Ethereum hash functions. Some popular options include:
ethhash: A Python library that calculates Ethereum hashes.
blockchain(a Node.js library): Provides a convenient API for working with Ethereum data structures.
In summary, Ethereum calculates transaction hashes by concatenating the previous block hash, the message header (signature), and the normalized input data. The resulting hash is then calculated using two hash functions: Keccak-256 and BLAKE2b. By following these steps and using a tool or library to help, you should be able to calculate 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 consult official resources and documentation from the Ethereum developers.