the backbone of Ethereum rollups

On this article we uncover what the sequencer node is, an important a part of the Ethereum -Rollup ecosystem.

This infrastructure entity is liable for a collection of processes that deliver the transaction knowledge on the L2 into the pinnacle -l1 and act as a connection level.

The operation and the diploma of decentralization of the sequencer have a direct affect on security, reliability and resistance to censorship of those options.

Let’s take a look at every thing intimately beneath.

What’s the sequencer and what’s his position within the EVM world

Within the panorama of scalability options for Ethereum, The sequencer is an entity that orders, carries out and combination off-chain transactions earlier than publishing on the layer-1 blockchain,. An important position is to enhance the scalability and effectivity of Layer 2 options, comparable to rollups, by decreasing fuel prices and dashing up the transaction finishes.

Technically outlined as a junction, the sequencer processes the transactions which are carried out on the rollups and encapsulates them right into a compressed “facet. “Then it sends this knowledge to Ethereum, the place they’re formally recorded and added to the first chain that’s liable for safety.

Relying on the structure of Layer-2, the sequencer could be centralized or decentralized and may affect vital features, such because the order of transactions, knowledge availability and censorship resistance.

Within the case of Optimistic rollupAs arbitrum and optimism, the sequencer orders the TX and publishes them on Ethereum assuming that they’re all legitimate, except disputed. In ZK-RollupAs Starknet and ZKSync, the sequencer not solely processes the transactions, but additionally generates cryptographic proof which are then verified on Ethereum. Lastly, in rollups of the Legitimate Kind comparable to Zkfair and Rhino.fi, a hybrid course of takes place as a result of the information is partially off-chain verified.

You will need to emphasize that this determine can also be utilized by different block chains and scalability options, however to stop confusion, we’ll solely consider the EVM world on this article. For information we level out There are parts analogue to sequencers in ecosystems comparable to Cosmos, Avalanche subnets and Celestia.

The Workflow of Sequencers within the varied Ethereum Rollups

We see that deeper into the completely different duties carried out by the sequencers, we see how they handle the life cycle of a transaction that’s carried out inside a rollup.

We will group their workflow 3 Basic steps: Accumulating and sorting transactions, implementation and publication about Ethereum.

1) Accumulating and sorting transactions

Customers ship transactions to the sequencer as a substitute of on to the L1, which get them organized in a selected block in response to an order technique. Normally we discover a “in Rollups“Public sale“Technique, the place an public sale takes place to find out the implementation order (those that pay extra reimbursements have precedence and are first ordered).

Different methods could be of the “Come first served first“Kind, the place transactions are accepted and processed within the order by which they arrive.

2) Implementation and calculation of the state

After figuring out the order of the transactions, the sequencer performs them domestically, in order that the standing of the Rollup Off-Chain is up to date.

This implementation is deterministic and follows the principles outlined by the good contract of the Rollup to L1, whereby the integrity of the operations is assured.

3) Batch manufacturing and publication on L1

At this level the transactions have been grouped in batches and despatched to L1 Ethereum.

The sequencer solely publishes the important knowledge (calldates) for knowledge availability (DA), in order that Ethereum can at all times reconstruct the state standing. This step ensures that the minimal calculation of use is used to maintain the L2 community prices low

Primarily based on the Rollup kind, these 3 steps can roughly differ significantly, as proven within the following desk.

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The issue of centralization of sequencer

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In the intervening time, most sequencers on Ethereum have been centralizedAs a result of virtually all Rollups have a single junction that’s liable for managing the connection between L2 and L1. This configuration is important within the “Internship 0“Phases of rollups, the place a compromise between decentralization and scalability is required to make all the infrastructure purposeful and environment friendly within the preliminary improvement part.

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With the occasions go forward with time, rollups are geared toward decentralizing their sequencers, introducing new options for sharing junctions and the federation, in order that they’re moved to “Section 1“And”Section 2. “Within the meantime, the extreme centralization of sequencers, even for a restricted interval, may, nevertheless, trigger severe structural issues for the related community on the second stage.

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To start with, the doorway of the management to a single node introduces a “Solely level of failure “: If the sequencer had an assault, technical failure or a manipulation, all the infrastructure might be affected, resulting in transaction inputs and even interruptions on the service. Furthermore, this energy focus can Threat of censorship on transactionsAs a result of the one operator would have the choice of randomly excluding or re -ordering transactions, in order that MEV methods are utilized.

One other vital side considerations to belief: The shortage of a distributed validation mechanism makes it tough for customers to confirm independently that transactions have been dealt with accurately. All this undermines the precept of decentralization that types the idea of the philosophy of Ethereum.

The centralization of junctions represents a double-edged sword: the sensible instance of the Layer-2 Linea.

Extreme centralization of sequencers is configured as a two -edged sword, Capable of actually save a full ecosystem from collapse, however on the identical time capable of result in a robust random censorship of the community.

What occurred with Layer-2 Linea in June final yr, throughout the hack and exploitation of the Velocore protocol, is a transparent instance of this.

On that event, throughout the cyber assault on the DEX, the Consensys workforce (which manages the Linea Rollup) determined Cease Block Manufacturing, “to dam“The sequencer. By doing this, virtually frozen with the chain, the Velocare workforce managed to regulate the incident, which resolves the code vulnerability. Within the meantime, Consensys censored the handle of the attacker, which made communication with the sequencer not possible (which, as we keep in mind, validates transactions and sends to L1).

If the sequencer was not closed, there would have been very severe financial penalties, with results, not solely on linea, but additionally on Ethereum.

The hackers may have pushed extra money from the weak good contracts, resulting in the exhaustion of the worth of the property primarily based on linea. Furthermore, the attacker may have modified the standing of the community, making it harder to detect and resolve the issue.

This might have had penalties for different Defi protocols which are related to linea, which signifies that many customers undergo liquidations or irreversible losses.

The Velocore Hack occasion led the Ethereum neighborhood to consider the Delicate stability between safety and decentralization. On the one hand, the speedy intervention of Consensys prevented a monetary catastrophe that protected customers and protocols in opposition to appreciable losses. However, the closure of the sequencer and the censorship of the handle of the attacker launched their concern in regards to the extreme centralized stream of Layer-2 operators.