The blockchain trilemma, proposed by Ethereum co-founder Vitalik Buterin, states that blockchain systems can only choose two of three properties: decentralization, scalability, and security. This trilemma often means making trade-offs when developing and building web3 infrastructure.

Data availability is crucial for all three sides of this triangle. It ensures that all network nodes can get the information they need to check transactions, reach consensus on new blocks, validate state transitions, and maintain overall network integrity. By having access to the full transaction and state data, nodes can independently verify the blockchain's history and current state, which is essential for decentralization and security.

If the data isn't reliably available, transactions happen slower, it's harder to achieve consensus, and Layer 2 solutions like rollups and sharding have trouble functioning. Therefore, ensuring the data is always available is vital for making a blockchain more scalable and improving its overall performance.

On Linea, data availability is a cornerstone of its scalability strategy. As a zkEVM Layer 2 solution, Linea relies on Ethereum for data availability by posting transaction data onto Ethereum's mainnet. This approach ensures that all data required for proof construction is accessible, enabling Linea to offer faster and cheaper transactions while maintaining security and decentralization.

Data availability in blockchain ensures that all necessary data for each block is accessible and verifiable by every node in the network. This means that the information needed to validate and confirm transactions is always available to all nodes.

Data availability supports the network's security, reliability, and decentralization, enabling blockchain systems to maintain integrity and functionality even in the face of potential failures or attacks. It underpins the ability of blockchain technology to provide a secure, transparent, and reliable digital ledger system, supporting principles of decentralization and trustless interactions. Here's how:

• Trust: Instead of relying on the honesty of block producers, nodes can independently verify transactions because they have access to all necessary data.

• Security: Ensures that all transactions are transparent and verifiable by all nodes, preventing fraud and tampering.

• Network Integrity: Without data availability, nodes cannot verify the completeness and correctness of transactions, potentially leading to network breakdowns.

Monolithic blockchains are like all-in-one devices, handling data availability, consensus, execution, and settlement in a single layer. This simplicity can make them easier to manage and potentially more secure but harder to scale as the network grows.

• Every node stores the entire blockchain, like each book club member having a full copy of every book.

• This ensures data is always available but increases storage requirements as the blockchain grows.

For example, Ethereum Layer 1 requires full nodes to store and verify the entire blockchain history, which can be hundreds of gigabytes.

Modular blockchains, on the other hand, are like a team of specialists, with each function in a separate layer. This setup is more complex but allows for better flexibility and scalability, as each layer can be optimized for its specific task.

• Data availability is managed by a specialized layer, like a librarian managing a master copy of all books.

• This improves data management and scalability.

• Other layers can focus on specific tasks, relying on the data availability layer.

Linea is a prime example, focusing on data availability and consensus layers. It ensures transaction data is accessible, allowing other layers to handle execution and validation, reducing the storage burden on individual nodes.

Linea is a zero-knowledge Ethereum Virtual Machine (zkEVM) that uses a modular architecture to improve scalability and efficiency. This modular approach ensures that data availability is maintained by publishing transaction data on Ethereum's mainnet, which is crucial for the network's security, scalability, and performance. It separates different blockchain functions into distinct layers:

1. Execution Layer: Linea handles transaction execution offchain, reducing the load on Ethereum L1.

2. Settlement Layer: This layer ensures that transactions are settled on Ethereum L1, providing finality and immutability.

3. Consensus & Data Availability Layer: Ethereum L1 ensures consensus and data availability, maintaining the integrity and security of processed transactions.

In contrast, a monolithic architecture combines execution, settlement, consensus, and data availability into a single layer, which can limit scalability and increase complexity.

Linea enhances Ethereum's scalability through mechanisms like batch processing and proof verification. By grouping transactions and utilizing zero-knowledge proofs, Linea efficiently reduces the load on Ethereum's main layer. Here is a breakdown:

• Transactions are processed in batches on Linea’s L2.

• Offchain execution reduces the load on Ethereum L1.

• Instead of processing each transaction individually, Linea groups multiple transactions into a single batch, processes them together, and posts the results to Ethereum L1.

• Linea generates zero-knowledge proofs after executing transactions.

• These proofs are posted to Ethereum L1 for verification.

• Ethereum L1 handles settlement, consensus, and data availability, ensuring the integrity and security of processed transactions.

Data availability is a fundamental aspect of Linea's architecture, ensuring that all necessary transaction data is accessible and verifiable by network participants. Here's how data availability on Linea operates:

• Offchain Execution on Linea: Linea leverages zkEVM capabilities to execute transactions offchain. For example, if 100 transactions are made, Linea processes them offchain and generates proof of their validity.

• Uploading Proofs to Ethereum L1: Linea uploads zero-knowledge proofs and necessary transaction data to Ethereum L1. This proof may consist of a summary of the transactions and a cryptographic assurance of their validity.

• Role of Ethereum L1: Ethereum L1 ensures that the transaction data is accessible and verifiable by all nodes, upholding the trustless nature of the network. Nodes can verify transactions using the posted proof and available data without needing to process each one individually.

To understand this mechanism, imagine a decentralized finance (DeFi) app on Linea. Users can make swaps and transfers. Instead of handling each transaction on Ethereum L1 individually, Linea processes them in groups offchain.

After processing, Linea creates a proof summarizing and validating all the batched transactions. This proof, along with necessary data, is then sent to Ethereum L1. Ethereum nodes can verify the proof to ensure the validity of all the batched transactions without needing to process each one individually.

Linea's modular architecture and use of Ethereum for transaction data exemplify how L2 solutions can enhance scalability while maintaining security and decentralization. By leveraging zero-knowledge proofs and batch processing, Linea reduces the load on Ethereum's mainnet, offering faster and cheaper transactions for decentralized applications (dapps), while ensuring data is accessible and verifiable by all network nodes. Key takeaways are as follows:

• Security: By utilizing Ethereum for data availability, Linea inherits the security and decentralization of the Ethereum network, ensuring that transaction data remains tamper-proof and accessible.

• Scalability: Linea's approach allows for increased transaction throughput and lower fees compared to Ethereum mainnet, while still maintaining data integrity and availability.

• Compatibility: As a Type 2 zkEVM, Linea maintains full compatibility with Ethereum's ecosystem, making it easy for developers to deploy and users to interact with dapps.

• Efficiency: The use of zero-knowledge proofs allows Linea to compress transaction data, reducing the amount of information that needs to be stored on Ethereum while still ensuring verifiability.

As blockchain technology evolves, data availability will remain essential for supporting scalable, secure, and decentralized networks, meeting the demands of a growing ecosystem.

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This article is part of our new series where we unpack beginner and advanced developer topics on Linea. Stay tuned and subscribe to Linea on Mirror for more coverage.