With Celestia announcing a new round of financing led by Bain Capital Crypto and Polychain Capital, modular public chains have once again become one of the hot topics of discussion. This article takes readers through the projects being built in the Celestia ecosystem: Cevmos, Fuel, dYmension, and Eclipse.
In short, a modular solution is a functional stack that modularizes the functions of a single blockchain. The specific functions can be roughly divided into:
Execution: handling state changes;
Settlement: verifying the state of the execution layer and resolving disputes, responsible for the bridge between assets and chains;
Consensus: all nodes reach a consensus on the validity of the state transition. In short, the nodes at least agree on the transaction and its order;
Data availability (DA): ensure that the data is storable, verifiable and available, that is, ensure that the transaction data behind the rollup block header has been published and available so that anyone can recreate the state.
Because a single blockchain cannot maintain the trustlessness and decentralization of the network by breaking the correlation between computing and verification costs while ensuring sufficient throughput. This bottleneck is also known as the "impossible triangle of blockchain".
Why do we need a modular public chain when we have rollup?
In fact, the two are not contradictory. In the past, the rollup we are familiar with only existed as the "vertical expansion" of the execution layer, while the modular blockchain solution led by Celestia realized the modularization of the settlement layer based on rollup, and made it possible to break the "impossible triangle of blockchain" by building a "horizontal expansion" of a modular stack.
Celestia's predecessor, LazyLedger, is a pluggable consensus and data availability layer that only verifies data availability and transaction ordering, providing great flexibility for the modular architecture of the entire blockchain network. Why is Celestia inseparable from rollup? Before modularization, the introduction of rollup has made how to verify the DA of Layer2 transaction data a major problem.
Specifically, when a block producer publishes a valid block header but deliberately hides or tampers with transaction data, light nodes can only rely on the block header for verification, so they are easily deceived and accept invalid blocks. Full nodes cannot generate DA and fraud proofs for light nodes, which means that light nodes have to verify DA themselves or assume that most data is credible. So, this is why most nodes must download all transaction data and verify the availability of block data. However, this will bring scalability limitations and problems to network expansion solutions.
Celestia uses an off-chain approach to implement DA, that is, Reed-Solomon erasure code and a specialized Namespaced Merkle Trees structure to ensure data availability, making DA cheaper and more efficient. The specific Celestia DA works as follows:
Nodes receive transactions submitted by rollup
Nodes ensure that appropriate fees are paid
Nodes sort transactions
Collectively verify the integrity of the data
Divide data according to the DNS mapping corresponding to the specific rollup inserted into Celestia
Of course, Celestia's core competitiveness lies not only in its DA and consensus functions, but also in its use of rollups to provide a variety of options for the execution layer. Celestia also divides rollups into Ethereum native and Celestia native. Celestia native rollups can be inserted into Celestia in two ways:
Sovereign rollups
Settlement Enforced rollups like Cevmos, Celestiums, etc.
It is worth noting that the biggest difference between the two solutions is whether the consensus layer is Ethereum or Celestia, and different teams have proposed different ideas about the two rollup buildable solutions.
Cevmos is a rollup stack jointly developed by Cosmos EVM application chain Evmos and Celestia, aiming to become the best settlement layer built on Celestia based on EVM rollup. Cevmos is the abbreviation of Celestia, Evmos and Cosmos.
As one of the mandatory settlement rollup solutions, Cevmos attempts to reduce costs and improve efficiency (restricted EVM) by providing a dedicated settlement layer for rollup. Specifically, in this stack, Cevmos will serve as a settlement layer, and will build a recursive rollup (rollup in rollup) of EVM on top of Evmos.
Cevmos uses Optimint (Optimistic Tendermint) instead of the Tendermint Core consensus engine used on the existing Cosmos to build Celestia rollup. Optimint is an alternative to Tendermint BFT, enabling developers to deploy rollups using existing consensus and DAs such as Celestia.
Since the Cevmos settlement layer is itself a rollup, rollups built on top of it are collectively referred to as settlement rollups. Each rollup built will have a two-way trust-minimized bridge with the Cevmos rollup, which can redeploy existing rollup contracts and applications on Ethereum to reduce the workload of migration. This also means that all rollups built will use calldata on the Cevmos rollup, and Cevmos uses Optimint to batch the data and publish it to Celestia.
Since the Cevmos rollup itself is a restricted EVM environment, they will also attempt to complete the challenge of the extreme setting through a single round fraud proof.
Cevmos not only tries to design and maintain a complex consensus mechanism without the need to design and maintain it, but also brings the efficiency of rollup and the interoperability of EVM to the entire Cosmos ecosystem, providing a practical solution for the popularization and use of modular solutions and the Cosmos ecosystem.
Fuel and Celestia are twin sisters. The difference is that Celestia is optimized for DA and sorting, and only handles data availability and consensus, while Fuel is positioned as a modular execution layer.
The biggest difference from today's Optimistic rollups is that Fuel runs a brand new virtual machine architecture, namely FuelVM and its toolchain and Sway language.
Fuel VM is a custom virtual machine built entirely for the execution of smart contracts, used to process transactions in parallel. Fuel VM was designed from the beginning to be easy to prevent fraud and can be used by the transaction execution layer of Optimistic rollup.
Additionally, FuelVM has features from WASM, EVM, and Solana's SeaLevel, but what differentiates it is that Fuel uses a UTXO model rather than an account model. Specifically, Fuel VM forces each transaction to explicitly define the UTXOs it will touch, and because the execution engine can accurately identify the state touched by each transaction, it can easily find undisputed transactions and parallelize them.
dYmension is a sovereign rollup built on Cosmos, designed to make rollApp (custom application-focused rollup) development extremely convenient through dYmension Chain (settlement layer), RDK (RollApp Development Kit), and IRC (inter-rollup communication).
dYmension's own settlement layer is called dYmension hub, which is a PoS chain with Tendermint Core state replication model for networking and consensus. RollApps built on the dYmension hub inherit the security of the hub, and the communication between them is guaranteed by the RDK and a dedicated set of modules supported by the hub.
RollApps consist of two core components: the client and the server. The server is the application end designated for the RollApp deployer, used to implement custom business logic and build pre-packaged modules of the RollApp Development Kit RDK. The client component, called dymint, is derived from Celestia's Optimint and is a direct replacement for Tendermint, responsible for block production, peer-to-peer message propagation, and inter-layer communication. Since RollApp itself has no consensus tasks, dymint can provide the low latency requirements required by modern applications.
Similar to Cosmos, dYmension RollApps aims to create application-specific blockchains to reduce consensus overhead. The RDK adds new modules and modifies existing modules on top of the Cosmos-SDK to ensure that RollApp is compatible with the dYmension protocol while still being compatible with other Cosmos ecosystem tools. RollApps can interact with any IBC-enabled chain using dYmension Hub, and are therefore part of the Cosmos ecosystem.
Eclipse is also a sovereign rollup based on the Cosmos ecosystem, allowing the use of Solana VM on any chain to build a customizable modular rollup settlement layer.
Eclipse will use Celestia as the consensus layer and DA in the early stages, and Solana VM as the settlement and execution environment. Its ultimate vision is to build a customizable rollup execution layer for any Layer1 heterogeneous blockchain, connecting all blockchains in a modular way. In addition, the settlement layer rollup built on Solana VM will also be iterated into Optimistic rollup and zk rollup in the future.
It is worth noting that the construction of the above modular solutions uses Celestia to provide data and Cosmos IBC to ensure inter-chain communication. Just like the Ethereum free ecosystem, a modular ecosystem based on Cosmos has been built, and the interoperability use cases of Cosmos will also usher in an explosion.
It is foreseeable that with the launch of the Celestia Fellowships project, more and more modular solutions will emerge, and we will be getting closer and closer to the final solution of the "blockchain impossible triangle". Perhaps, the narrative of blockchain modularity will also be opened up.
