Ethereum is a decentralized blockchain network that allows developers to build and deploy decentralized applications (dApps). To function properly, Ethereum requires methods for storing data in a secure and decentralized way. This article will provide an overview of Ethereum’s storage mechanisms and technical concepts around data storage.
Ethereum Account Storage
The Ethereum network stores data related to user accounts. This includes:
Ethereum Addresses
Ethereum addresses are used to identify user accounts on the network. An address is derived from the public key of an Ethereum account. Addresses are used to transfer ETH and tokens to other accounts.
Account Balances
The Ethereum network keeps track of the ETH and token balances for every account address. This allows the network to verify if an account has enough ETH to send a transaction.
Smart Contract Code
Ethereum stores the programming code of deployed smart contracts. This code gets executed when transactions are sent to the contract. The code is stored permanently on the blockchain.
Smart Contract State
In addition to code, the data values or “state” that a smart contract is currently set to are stored. This includes balances, structs, mappings, etc.
Decentralized Storage on Ethereum
Along with account data, Ethereum offers decentralized solutions for storing app data in a censorship-resistant and tamper-proof way:
Swarm
Swarm is a peer-to-peer file sharing protocol that allows decentralized apps to store and distribute large volumes of data in a decentralized way. Files are split up, encrypted, and spread across nodes on the Swarm network.
IPFS
The InterPlanetary File System (IPFS) is another P2P network that allows storage and sharing of files in a decentralized manner. IPFS uses content-addressing to uniquely identify files by their hash instead of location. This integrates well with Swarm and Ethereum.
State Storage in Ethereum
Ethereum client software like Geth needs to keep track of the current world state – account balances, contract code and storage, etc. This is accomplished via state storage mechanisms like:
State Database
Ethereum stores the world state in a database like LevelDB. This allows fast retrieval of current account and contract data to serve requests and verify transactions.
State Trees
Ethereum uses Merkle Patricia trees to store state data. This allows efficient storage and verification of chain state by hashing tree branches. The root hash represents the entire world state at a block.
State Pruning
To prevent infinite growth, temporary and old state entries can be cleared by pruned after usage. Only recent state required by active contracts is kept.
Stateless Clients
Light nodes can run in stateless mode where they don’t store long-term blockchain state. They verify it temporarily by syncing relevant parts of the state tree from archive nodes on-demand.
Long-term Storage on Ethereum
Storing historical blockchain data in a decentralized secure way for the long-term is crucial as well:
Full & Archival Nodes
Full Ethereum nodes store the complete blockchain data including historical state tree entries, allowing them to independently verify and serve all on-chain data since Genesis.
Client Databases
Full node clients like Geth and Parity have their own database formats to efficiently store and retrieve chain data including blocks, transactions, accounts, state entries etc.
Node Incentivisation
Methods to incentivize storage of voluminous history by archival nodes is an active area of research. This could include storage rents, data availability sampling, and slashing for failing to provide historical data.
Private Data Storage
While Ethereum focuses on public transparency of on-chain data, private and encrypted data storage methods are in development:
Zero-Knowledge Proofs
ZK-SNARKs and STARKs allow validation of correct data without revealing actual private data through cryptographic proofs. This enables private smart contracts.
Trusted Execution Environments
TEEs like Intel SGX use hardware-enforced privacy to protect code and data while computing. This facilitates privacy in decentralized computation and storage.
State Channels
By transacting and storing data off-chain peer-to-peer over state channels, users can keep data private until channel closure back on-chain. Raiden is an example project enabling private tokens and payments.
Conclusion
Ethereum offers a diverse array of storage mechanisms to users and developers, both on-chain and off-chain. These include accounts, smart contracts, decentralized file systems, private data schemes, databases and more. Many innovations are still taking place to scale decentralized storage for global adoption while retaining privacy and security guarantees. The active research makes Ethereum data storage capabilities ever-evolving.
Frequently Asked Questions
What data does the Ethereum blockchain store?
The Ethereum blockchain stores account data like addresses and balances, smart contract code and state, and transaction details in blocks. This on-chain public data is necessary to independently verify the state and history of the network.
How is data stored on Ethereum nodes?
Ethereum client software uses optimized databases like LevelDB to quickly store, retrieve and serve blockchain data to applications. Storage schemes like state trees with pruning are used to efficiently track current world state.
Can data be stored privately on Ethereum?
Yes, through innovations like zero-knowledge proofs, trusted execution environments, and state channels, private data storage and transactions are possible on Ethereum sidechains and layer-2 systems.
What incentives exist for storing historical blockchain data?
Archival nodes that store and serve full historical blockchain data are crucial infrastructure. Network incentives including payment for serving old data are in research and development.
How can traditional cloud storage integrate with Ethereum?
Decentralized file systems like IPFS and Swarm bridge traditional web2 cloud storage with web3 by allowing protected, encrypted cloud storage of data via content addressing. This data can interact trustlessly with smart contracts.
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