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The Impossible Trinity and Data Availability Problem The Impossible Trinity, also known as the Trilemma, usually refers to the fact that decentralization, scalability, and security cannot be achieved at the same time. It was first proposed by Ethereum officials.

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When a transaction is put on the chain, it first enters the Mempool, where it is "selected" by miners, packaged into blocks, and spliced ​​into the blockchain. The block containing this transaction will be broadcast to all nodes in the network. Other full nodes will download this new block, perform complex calculations, and verify each transaction in it to ensure that the transaction is true and valid. Complex calculations and redundancy are the foundation of Ethereum's security, but they also bring problems.

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Data availability issues There are usually two types of nodes: Full nodes - download and verify all block information and transaction data. Light nodes - easy to deploy, only verify the block header (data summary). First, ensure that when a new block is generated, all the data in the block has been published so that other nodes can verify it. If the full node does not publish all the data in the block, other nodes cannot detect whether the block hides malicious transactions.

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If a full node conceals some transaction data, other full nodes will refuse to follow this block after verification, but the light node that only downloads the block header cannot verify and will continue to follow this forked block, affecting security. Although the blockchain will confiscate the full node's deposit, users who pledged to the node will also suffer losses. And if the evil benefits exceed the cost, the node has the motivation to conceal.

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On the other hand, if the full node deployment is gradually centralized, there is a possibility of collusion between nodes, which will endanger the security of the entire chain. This is why data availability is important. Data availability is getting more and more attention, on the one hand because of the Ethereum PoS merger, and on the other hand because of the development of Rollup. Currently, Rollup runs a centralized sequencer.

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When users trade on Rollup, the sequencer sorts, packages, and compresses the transactions and publishes them to the Ethereum mainnet. The mainnet full node verifies the data through fraud proof (Optimistic) or validity proof (ZK). As long as all the data of the block submitted by the sequencer is authentic and available, the Ethereum mainnet can track, verify, and reconstruct the Rollup state based on it to ensure data authenticity and user property security.

3/State Explosion and Centralization

State explosion means that the Ethereum full node accumulates more and more historical and state data, and the storage resources required to run the full node are increasing, the operating threshold is increased, and the network nodes are centralized. Therefore, there needs to be a way to enable the full node to synchronize and verify block data without downloading all the data, but only download some redundant fragments of the block.

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So far, we understand that data availability is important. So, how to avoid the "tragedy of the commons"? That is, everyone knows the importance of data availability, but there still needs to be some tangible interest drive to make everyone use a separate data availability layer. Just like everyone knows that protecting the environment is important, but when you see garbage on the roadside, why should "I" pick it up? Why not others? What benefits can "I" get from picking up the garbage?

5/What is Celestia?

Celestia provides a pluggable data availability layer and consensus for other Layer1 and Layer2, built on the Cosmos Tendermint consensus and Cosmos SDK.

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#Celestia is a Layer1 protocol that is compatible with EVM chains and#Cosmosapplication chains. In the future, it will support all types of Rollups. These chains can directly use Celestia as the data availability layer. Block data will be stored, called, and verified through Celestia, and then returned to its own protocol for settlement. Celestia also supports native Rollups and can directly build Layer2 on it, but it does not support smart contracts, so dApps cannot be built directly.