Clear DefinitionsAccount Model
1 min read
Pronunciation
[uh-kount mod-l]
Analogy
The account model works like a traditional bank account system. Each person has an account with a current balance, and transactions simply add to or subtract from these balances. When you send money, your account balance decreases, and the recipient's increases, without needing to track individual 'bills' or previous transactions.
Definition
A blockchain architecture that tracks user balances and state through accounts with associated storage, rather than through unspent transaction outputs. The account model maintains the global state as a mapping of account addresses to their balances and data.
Key Points Intro
The account model provides an intuitive state management approach for complex blockchain applications.
Key Points
Tracks balances and state directly in accounts rather than through transaction outputs.
Simplifies smart contract implementation by maintaining persistent storage for each account.
Reduces transaction size by eliminating the need to reference previous transactions.
Used by Ethereum and many other smart contract platforms.
Example
In Ethereum's account model, when you send 5 ETH to a friend, the transaction simply reduces your account balance by 5 ETH (plus gas fees) and increases your friend's balance by 5 ETH, without needing to reference specific previous transactions that gave you those coins.
Technical Deep Dive
Blockchain account models typically distinguish two account types: (1) Externally Owned Accounts (EOAs) controlled by private keys, and (2) Contract Accounts containing executable code and state. Both maintain balances, but contract accounts also have persistent storage and code that executes when called. Account state is typically maintained in structures like Merkle Patricia Tries (Ethereum) or AVL trees (Cosmos), with each account's current state derived from the cumulative effect of all transactions affecting it. This differs fundamentally from the UTXO model where state is implicitly derived from unspent outputs. The account model simplifies complex state transitions and enables more intuitive smart contract programming, but creates challenges including potential state bloat (as all accounts must be stored permanently), replay attack vectors requiring explicit nonce management, and synchronization bottlenecks when multiple transactions affect the same accounts. Advanced implementations address these issues through state rent (charging for storage), more efficient state proof structures, and parallelization of unrelated account updates.
Caveat
While the account model simplifies many aspects of blockchain design, it creates challenges for parallelization since transactions affecting the same account must be processed sequentially to maintain consistent state. This can create performance bottlenecks not present in UTXO-based systems where unrelated transactions can be processed in parallel.
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