Ethereum accounts, fundamental to the blockchain, hold ether (ETH) and can initiate transactions․ There are two types: Externally Owned Accounts (EOAs), controlled by users, and contract accounts, governed by smart contract code․
Table of contents
Account Data
Each Ethereum account holds crucial information:
- Nonce: Transaction counter․
- Balance: ETH balance․
- Code (for contracts): Smart contract code․
- Storage (for contracts): Contract data․
Balance Storage
The balance represents the amount of ETH held by an account․ It’s a core attribute, updated with each transaction․ Smart contracts utilize storage to maintain their internal state and data, separate from the account’s ETH balance․ Storing data on the Ethereum blockchain offers benefits like security․
How Balances are Stored in Ethereum
Understanding how Ethereum stores account balances requires delving into the underlying data structures that power the blockchain․ Ethereum uses a modified Merkle Patricia Trie, often referred to as a Merkle Trie, to efficiently store and retrieve account data, including balances․
Merkle Patricia Trie
A Merkle Trie is a data structure that provides a cryptographically secure and efficient way to store key-value pairs․ In Ethereum’s context:
- Key: The account address (a 160-bit identifier)․
- Value: The account state, which includes the nonce, balance, storage root, and code hash․
The state trie is a global data structure that maps account addresses to their corresponding account states․ It’s a single, massive trie that represents the entire state of the Ethereum blockchain at a given block․
Storage Details
- Account State: Each account’s state is serialized into a byte string and stored as the value in the state trie․ The balance is a part of this serialized account state․
- Key-Value Lookup: When you want to know the balance of an account, the Ethereum client performs a lookup in the state trie using the account address as the key․ The trie efficiently navigates through its nodes to locate the account state associated with that address․
- Updates: When a transaction changes an account’s balance (e․g․, sending or receiving ETH), the corresponding account state in the state trie is updated․ This involves recalculating the Merkle root of the trie, ensuring the integrity and immutability of the blockchain․
- Immutability: While the balance changes, the old states are not deleted․ Ethereum maintains a history of all state changes, allowing for auditing and verification․ Each block contains the root hash of the state trie at that point in time․
Benefits of the Merkle Trie
Using a Merkle Trie for storing account balances provides several advantages:
- Efficiency: Efficient lookup and updates of account states, even with millions of accounts․
- Cryptographic Security: The Merkle root provides a cryptographic commitment to the entire state of Ethereum․ Any modification to an account’s balance will change the Merkle root, making it easy to detect tampering․
- Light Clients: Light clients can verify specific parts of the state (like an account’s balance) without downloading the entire blockchain․ They can request a Merkle proof for the account’s state, which allows them to verify its authenticity against the Merkle root in a block header․
Considerations
While Merkle Tries are efficient, they also have some limitations:
- Storage Costs: Storing data on the Ethereum blockchain is expensive due to the limited block size and the gas costs associated with transactions․
- Computational Overhead: Updating the state trie requires significant computational resources, which contributes to the gas cost of transactions․
