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Understanding How Ethereum Nodes Find Transactions on the Blockchain

Ethereum nodes play a crucial role in maintaining the integrity and accessibility of the blockchain. A node is essentially a computer that runs the Ethereum software, allowing it to validate transactions and store them on-chain. However, finding specific transactions or UTXOs (unspent transaction outputs) can be difficult. In this article, we’ll learn how nodes find these transactions on the blockchain.

What are Merkle Branches?

A Merkle branch is a tree structure used to represent the hash of a collection of data. It allows for efficient storage and retrieval of large amounts of data, such as transaction hashes or UTXO values. When a node receives a new transaction or UTXO, it creates a Merkle branch containing a unique combination of that data.

How ​​does a node find a specific transaction?

When a SPV (light) client asks a full node for the Merkle branch containing a specific transaction, here’s what happens:

• Node fetches data: The node sends its current database to the full node, which stores it in memory.

• Merkle branch creation: The node creates a Merkle branch using the data retrieved from its database and the UTXO value of interest (the specific transaction).

• Hash function

  : The node uses a hash function to combine the Merkle branch with an empty string, creating a unique digital fingerprint.

• Merkle tree construction: The node builds a Merkle tree by recursively combining the hashes from step 3 until it finds the desired Merkle branch (i.e., the Merkle branch containing the specific transaction).

• Node returns Merkle branch: The full node sends the constructed Merkle branch to the SPV client, which can then use this information to verify the transaction.

What about UTXOs?

Similarly, when a node finds an address (UTXO value), it creates a Merkle branch containing its associated data. However, UTXOs do not have a fixed Merkle branch because they are not directly tied to a specific transaction hash. Instead, nodes use the
Merkle tree to verify the integrity of transactions and ensure that all valid UTXOs are included.

In short, Ethereum nodes use a combination of hashing, data structures (such as Merkle trees), and computing power to efficiently store and retrieve specific transactions or UTXO values ​​from the blockchain. By creating a Merkle branch using the data retrieved from its database and the relevant UTXO value, nodes can verify the integrity of the transaction and ensure that it is valid to be included in the blockchain.

Conclusion

Understanding how Ethereum nodes find transactions on the blockchain is essential to building efficient and secure applications on the Ethereum network. By leveraging advanced data structures such as Merkle trees, nodes are able to efficiently store, retrieve, and validate transactions and UTXOs, ensuring the integrity of the entire chain.

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