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Announcement

The Ethereum rollup ecosystem has witnessed another critical milestone - the apparent launch of zkEVM (Zero-Knowledge Ethereum Virtual Machine) on the mainnet by Ethereum Layer 2 network Scroll. This milestone, which has unfolded with minimal fanfare, has already seen $500,000+ bridged to the platform, involving 500+ unique users. Despite the absence of an official announcement from the Scroll team, the deployment of this bridge commenced on October 8th, as revealed by blockchain explorer Etherscan.

What is Scroll?

Scroll in an EVM-compatible ZK-Rollup that will help scale Ethereum Mainnet through the standardization of the layer-2 proof outsourcing market.

Scroll's Technology

Scroll aims to be a layer-2 blockchain protocol that provides scaling solutions for the Ethereum mainnet. At its technical core, Scroll is being developed as a zero-knowledge rollup (ZK-rollup). ZK-rollups create large bundles of transactions for off-chain computation in the form of cryptographic proofs known as SNARKs. The SNARKs serve as a validating proof between the layer-2 data and the mainnet, giving a rollup like Scroll the advantage of maintaining layer-1 security with layer-2 finality speeds.

Scroll will support direct mainnet Ethereum validation through a single succinct proof. In many ways, Scroll operates in reverse of typical zk-rollups and utilizes the EVM with custom optimizations to significantly boost Scroll block finality speeds while remaining compatible with all Ethereum infrastructure.

Scroll's Rollup Architecture

All the core infrastructure of the Scroll network relies on the success of the zkEVM. Prior to Scroll’s attempt, a successful native EVM circuit had never been constructed. Scroll aims to be the first to identify and address previously unsolved issues with the concept.

Broad overview of zkEVM architecture | Source​​​​​​

Scroll's system architecture surrounding the zkEVM design has been made possible through recent breakthroughs, including:

• Polynomial Commitment - This allows a system to operate a circuit without size constraints that previously made circuits inefficient
• Customized Gadgets - The usage of lookup tables and customized gadgets reduces overall overhead for EVM circuit design
• Overall Hardware Acceleration - Advancements in GPU / CPU speed and other hardware components are making systems like EVM circuits more feasible, including a custom write-up from the Scroll team outlining a 5x improvement over Filecoin's GPU

These advancements allow for the zkEVM design to function, paving the way forward for the layer-2 architecture of the system to be built around it. In this architecture, we find three core pieces of infrastructure.

Those three pieces are:

• Scroll Node
• Roller Network
• Rollup & Bridge Contracts

The Scroll node is what formally creates the blocks and commits them to the Ethereum Mainnet layer. In other words, the nodes on Scroll are the messengers between the layer-1 and layer-2 networks. The nodes have three different components: sequencer, coordinator, & relayer.

Scroll architecture.

Rollup Sequencers and Provers

Sequencers receive the layer-2 transactions in batches and then generate layer-2 blocks with that information. After the sequencer generates a new block, the coordinator is notified and executes a trace before dispatching the execution trace to a roller. The roller is a part of the Roller Network, which operates through a decentralized, random leader selection algorithm to generate a proof.

Rollers serve as the ‘provers’ of the system in that they hold the responsibility of generating validation proofs for the rollup. Each zkEVM circuit has a generated proof from the Roller Network. Prior to releasing these proofs, they are combined into a single block proof to speed up block finality & overall efficiency. This idea also relies on the rollers utilizing top-of-the-line GPUs and other hardware.

Roller workflow.

Two sets of smart contracts make the Scroll rollup functionality possible: rollup contracts and bridge contracts. The rollup contracts receive the layer-2 blocks from the sequencer and then store the state roots in the Ethereum state in the form of calldata. This does two things:

• Ensures layer-2 block data is always available
• Gives Scroll the advantage of using Ethereum's security

The other side of this process is the bridge contracts. These are deployed on both systems (Scroll & Ethereum) as a network messaging protocol. On top of this messaging protocol rests an ERC-20 token bridging protocol that users can leverage to transfer tokens in either direction.

Scroll workflow.