StarkNet is a decentralized, zero-knowledge (ZK) rollup that aims to bring scalability and privacy to the Ethereum ecosystem. One of the key features of StarkNet is its unique state and storage model, which differs significantly from the traditional Ethereum model. In this article, we’ll dive deep into the intricacies of StarkNet’s state and storage model, exploring its key components and how they work together to provide a secure and efficient blockchain solution.
In StarkNet, the state of the blockchain is represented by a Merkle tree, where each leaf node represents the state of a specific account. The root of this Merkle tree is called the state commitment, and it serves as a compact representation of the entire state of the network.
As transactions are processed and the state of the blockchain changes, the state commitment is updated to reflect the new state. The updated state commitment is called the state root, and it is included in the block header, allowing anyone to efficiently verify the state of the blockchain at a given point in time.
When a transaction is executed on StarkNet, it triggers a state transition, where the state of the blockchain is updated from one state root to another. These state transitions are verifiable using zero-knowledge proofs, ensuring that the new state root is consistent with the previous state root and the executed transaction.
The following diagram illustrates the state transition process in StarkNet:
graph LR
A(Previous State Root) --> B(Transaction)
B --> C(State Transition)
C --> D(New State Root)
D --> E(Block Header)
In StarkNet, each account has its own storage, which is organized into memory slots. These memory slots are essentially key-value pairs, where the key represents the address of the storage location, and the value represents the data stored at that location.
Similar to the state commitment, the storage of each account is also represented by a Merkle tree, where the leaf nodes correspond to the memory slots. The root of this Merkle tree is called the storage commitment, and it serves as a compact representation of the entire storage of the account.
When a contract needs to access the value stored at a specific memory slot, it must provide a storage proof. This proof consists of a Merkle proof that the requested memory slot is part of the account’s storage commitment. This allows the contract to efficiently verify the correctness of the retrieved data without having to download the entire storage of the account.
The following table compares the state and storage models of StarkNet and Ethereum:
| Feature | StarkNet | Ethereum |
|---|---|---|
| State Representation | Merkle tree | Patricia trie |
| State Commitment | Root of state Merkle tree | Root of state Patricia trie |
| State Transitions | Verified using zero-knowledge proofs | Verified using block validation |
| Storage Representation | Merkle tree per account | Patricia trie per account |
| Storage Commitment | Root of storage Merkle tree | Root of storage Patricia trie |
| Storage Proofs | Merkle proofs | Blockchain state querying |
In StarkNet, state refers to the overall state of the blockchain, including account balances, contract code, and other global information. Storage refers to the persistent data stored within individual contracts, organized into memory slots.
State commitments and state roots are used to represent the state of the blockchain in a compact and efficient manner. The state commitment is the root of the Merkle tree that represents the entire state, and the state root is the updated state commitment after a state transition. These values are used to verify the correctness of the blockchain state without having to download the entire state.
Storage proofs in StarkNet allow contracts to efficiently verify the correctness of data retrieved from their own storage. By providing a Merkle proof that the requested data is part of the storage commitment, contracts can ensure that the data has not been tampered with, without having to download the entire storage.
The key differences are:
The main benefits of StarkNet’s state and storage model are:
StarkNet’s state and storage model is a crucial component of its overall architecture, designed to address the scalability and privacy challenges faced by traditional blockchain systems. By leveraging Merkle trees, zero-knowledge proofs, and storage proofs, StarkNet aims to provide a secure and efficient platform for decentralized applications. As developers continue to explore the capabilities of this innovative technology, a deep understanding of the state and storage model will be essential for building cutting-edge dApps on the StarkNet network.