Ethereum’s “The Merge” to the proof-of-stake network is scheduled to go live on mainnet at the end of September. Its goal is to unlock blockchain accessibility at scale. At its core, the merger transformed Ethereum from a Bitcoin-style proof-of-work consensus mechanism to a proof-of-stake system. Ethereum’s move from performing sharding to a rollup-centric roadmap is a critical step in scaling the blockchain for the next billion users. Data availability and sharding in a modular architecture allows blockchains to scale throughput without sacrificing decentralization. This article will dive into the technical details of the merger, Ethereum’s new roadmap, and what the change means for users and developers.
A Rollup-Centric Roadmap
Originally, the plan for Ethereum 2.0 (the now deprecated term) was to achieve scalability by dividing the mainnet into 64 shards, each with individual miners/validators. Then, based on congestion, utilization, and throughput, users will send transactions that are routed to specific shards. Due to the rise and adoption of rollups, and the complexity of execution sharding implementations, the original execution sharding-centric scalability roadmap has been abandoned in favor of data sharding. The Ethereum team now believes that the rollup will extend Ethereum to meet the needs of the world, and the plan for the combined Ethereum is to become a robust settlement and data availability layer from which the rollup derives its security.
Source: ETH2 Book
Beacon Chain (The Merge)
Contrary to popular belief, the purpose of the merger is not to reduce transaction costs, but to transform Ethereum into a powerful underlying infrastructure layer for rollups. The first core step towards this goal is the Beacon Chain. This transforms Ethereum from its previous proof-of-work system to a proof-of-stake system, in which stakeholders must submit collateral to produce blocks, and the collateral of dishonest participants is slashed. Moving the consensus system to proof-of-stake introduced a validation committee as a foundation, which in turn strengthened network consensus and paved the way for an efficient layer of data availability within the protocol.
The Beacon Chain guides and coordinates the network of stakeholders without processing or executing transactions like Ethereum does today. More specifically, what the merger does is merge the old Ethereum execution layer with the new consensus engine provided by the beacon chain, which will leverage the current algorithm of proof-of-work miners with a coordinated network exchange of proof-of-stake validators. Switching the consensus algorithm also sets the stage for sharding: previously, in proof-of-work mining, there was no miner registry, and miners could arbitrarily stop their duties and leave the network. Under the proof-of-stake mechanism, the beacon chain now has a registry of all approved block producers and can coordinate and parallelize validator voting.
Source: ETH2 Book
Groups of validators, committees, are a key innovation provided by the beacon chain. The beacon chain random allocation committee votes on the block to form a consensus. The committee’s combined votes are called “attestations,” and by examining the committee’s votes, the state of the beacon chain can be easily verified, minimizing block size and data growth compared to single-validator verification. The accreditation committee also strengthens consensus, as in this model a relatively large number of validators are required to co-create the fork. In addition, the validator set changes periodically, making it difficult for malicious validators to collude in time to attack.
Consensus and MEV (The Splurge)
After the merger, Ethereum will implement proposer-builder separation for the consensus layer. Vitalik believes that the endgame for all blockchains is to have centralized block production and decentralized block verification. Since the sharded Ethereum block data is very dense, the centralization of block production is necessary due to the high requirements for data availability. At the same time, there must be a way to maintain a decentralized set of validators that can validate blocks and perform data availability sampling.
The new builder role builds the Ethereum execution payload block using user transactions and submits it along with bids from proposers (a randomly selected subset of the validator set). Once the proposer accepts the payload, they sign the block and propagate it through the network. Since the payload sent to the proposer is stripped of the transaction content, this structure eliminates the possibility of a validator preempting a transaction. In an efficient market, the introduction of a blockspace market would also incentivize builders to bid up to the full value of the MEV extracted, allowing a decentralized set of validators to receive most of the MEV reward. Compared to emulating Ethereum, this setup prevents miners from potentially volatile consensus and mitigates harmful MEV.
Danksharding (The Surge)
While the proposal-builder separation was originally designed to counteract the harmful externalities and centralizing forces of MEV, the Ethereum core team realized that it could also serve the purpose of data sharding.
Named after core contributor Dankrad Feist, Danksharding’s main innovation is a consolidated fee market – instead of a fixed number of shards with different blocks and proposers, one proposer chooses all transactions and data. Proposers are a randomly selected committee of validators who subsequently perform data availability sampling on the blockchain data. This ensures a decentralized way to maintain data availability for light clients, since the merged block data is too large for a single point of verification to be possible. Since consensus nodes are also performing data availability sampling, the model unifies the settlement layer, consensus layer, and data availability layer.
The unified settlement and data availability layer utilizes proof-of-validity to unlock exciting capabilities for rollup: ZK rollup will now be able to make synchronous calls to the execution layer on Ethereum. This enhances new L2 primitives such as distributed liquidity and fractal scaling, laying the foundation for building innovative next-generation dapps on ZK rollup.
Although danksharding has a good impact on the future of Ethereum, it will not be fully available immediately after the merger. Proto-dank sharding (EIP-4844) is the original version of danksharding planned for release before full implementation. The proposal creates a primitive called carry blob transactions. As the name suggests, a blob-carrying transaction is a transaction that carries a data payload called a blob. Blobs are the data standard for post-shard Ethereum: they are bundled with KZG polynomial commitments and are more efficient than the calldata format due to decoupling from the EVM execution.
Currently, rollup uses calldata to send transaction data back to Ethereum, resulting in high gas costs. In the future of sharding, rollup will use blobs, saving users gas costs associated with EVM execution. The goal of Proto-danksharding is to provide developers with this forward-looking data format, while providing a temporary relief from the rollup of expensive calldata costs by introducing a separate format and fee market for data about to be sharded. While proto-danksharding itself does not really implement sharding, introducing standardized specifications for post-sharded data formats is the first step in building an efficient native data availability layer.
History and Status (The Verge & The Purge)
Ethereum state and its storage are also a consideration. The ever-increasing state could potentially impact decentralization, as validators must be able to complete their tasks on consumer hardware. The Proto-danksharding blob is separate from the EVM execution layer and will be removed after about a month. Additionally, EIP-4444 allows clients to delete and stop serving historical data on the peer-to-peer layer after about a year. In any case, enforcing some type of forced history expiration at the protocol level is necessary because post-sharding will add about 40 TB of historical blob data per year. The blockchain state needs to be stored on RAM or SSD. However, historical storage, data that Ethereum has agreed upon, can be stored on cheap HDDs. Since history storage operates on an honest minority (1/N) trust model, it is not necessary to store history data on nodes that perform real-time consensus. The Danksharding specification ensures that validators store and guarantee the availability of the data they reach consensus within months. These pruned histories are then stored by third parties, such as application-specific protocols, BitTorrent, portal networks, block explorers, individual hobbyists, or indexing protocols.
Stateless Ethereum is another goal on the roadmap. Block producers who construct blocks will utilize witnesses, which are proofs consisting of relevant data needed to execute the transactions contained in the block. Therefore, clients use this witness to verify the state root resulting from executing a block, and only need to execute part of the affected state, not the entire state. The two main obstacles to this design are the scale of the witness and the availability of the witness. The first problem can be solved by changing the state data structure in Ethereum, from Merkle Patricia Tries to Verkle Tries, a more efficient data structure for the polynomial commitments that Ethereum uses after the merger. The second problem can be solved by making block witnesses a protocol-level specification. Following Vitalik’s conclusion in Endgame, relying on centralized block producers with specialized hardware while maintaining decentralized verification is a key design framework for scaling Ethereum.
Danksharding enhances the rollup of security inherited from Ethereum. Upgrading the underlying infrastructure by tightly coupling data availability to the consensus and settlement layers allows rollup to leverage native data availability solutions, abandoning the security assumptions of validium and volition. This paves the way for an architecture like the enshrined rollup, which removes governance and smart contract risks by allowing the entire rollup to be deployed within the protocol. Rollup using SNARK for intra-protocol synchronous calls becomes a promising design for future blockchain expansion. In-protocol rollup has many benefits: the fixed, per-block gas cost faced by smart contract rollup is now eliminated, when computation is decoupled from consensus, validators need to re-execute transactions to validate a block, and there is no State clients no longer need to download witnesses, as state differences are now guaranteed through the properties of validity proofs. These benefits include lower settlement latency, better synchronization, higher validator bandwidth (and thus higher EVM gas limit), and more secure cross-chain bridging. The Ethereum Foundation is currently working on implementing this design directly into the Ethereum roadmap, with plans to upgrade the EVM to SNARK-compatible enshrined rollups.
The main goals of the Ethereum roadmap are to minimize trust assumptions and provide in-protocol scalability by enabling native solutions. The base layer of Ethereum hosts an entire ecosystem of decentralized applications, poised to fundamentally change the way we think about identity, storage, search, reputation, and privacy in the digital age. Upgrading Ethereum to a base layer also elevates this application layer, benefiting users and developers by providing a highly secure, robust infrastructure to scale these use cases globally. Ethereum’s vision is a digital future on a global scale. Its adherence to the principles of trusted neutrality and Ethereum’s network effects, decentralization, and security firmly cements its role in the decentralized web of the future. The merger is the first step in Guarding Ethereum’s realization of this vision.
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