Scroll

Scroll's primary value proposition is Ethereum-equivalent compatibility. Developers can deploy existing EVM smart contracts and use familiar tools (Hardhat, Foundry, MetaMask) with minimal to no modifications. This is achieved through its zkEVM architecture, which generates cryptographic proofs for EVM execution.

The official Scroll Bridge is the canonical method for moving assets between Ethereum L1 and Scroll L2. It supports ETH and ERC-20 tokens.

• Native ETH: ETH on Scroll is the native gas token.
• Bridged USDC & DAI: Major stablecoins are available via canonical bridges from Ethereum.
• Fast Withdrawals: Users can initiate withdrawals that are finalized faster than the standard challenge period, often via third-party liquidity providers.

The ecosystem features foundational DeFi primitives and infrastructure services.

• DEXs & AMMs: Protocols like SyncSwap, Izumi Finance, and Ambient Finance provide liquidity and swapping.
• Lending Markets: Scroll Lend (Compound fork) and LayerBank offer lending/borrowing.
• Native Oracles: Pyth Network and Supra provide price feeds.
• Account Abstraction: Biconomy and ZeroDev enable smart contract wallets and gas sponsorship.

A suite of applications focuses on improving user accessibility and discovery.

• Bridging Aggregators: Orbiter Finance and Layerswap offer alternative bridging routes.
• Gas Solutions: Gas Zip provides gas abstraction.
• Explorers: Scrollscan is the primary block explorer.
• Faucets: Community faucets provide testnet ETH for developers.

Scroll integrates with broader cross-chain ecosystems to enhance liquidity and connectivity.

• Messaging Layers: Connected to LayerZero and Axelar for generic message passing.
• Modular Stack: Uses EigenDA for high-throughput, low-cost data availability, part of the EigenLayer ecosystem.
• Rollup-as-a-Service: Partners like Caldera and AltLayer offer custom rollup deployment using Scroll's tech stack.

The Scroll Ecosystem Grant Program and Scroll Marks initiative are designed to bootstrap sustainable growth.

• Grants: Fund projects in DeFi, infrastructure, NFTs, and social.
• Scroll Marks: A loyalty points system tracking user engagement with ecosystem dApps, often seen as a precursor to potential future token distribution.
• Developer Support: Includes technical guidance, co-marketing, and access to investor networks.

Scroll's core security guarantee is derived from Ethereum. It uses zk-SNARKs (Zero-Knowledge Succinct Non-Interactive Arguments of Knowledge) to generate cryptographic proofs of correct state transitions. These proofs are verified on the Ethereum mainnet, ensuring the Layer 2's execution is valid without requiring L1 to re-execute transactions.

• Finality: A state root is finalized on Ethereum only after its validity proof is verified.
• Data Availability: Transaction data is posted to Ethereum's calldata, ensuring it's publicly available for reconstruction and fraud detection.

Scroll separates the roles of transaction sequencing and proof generation to optimize for performance and decentralization.

• Sequencer: Batches user transactions, orders them, and posts the data to Ethereum. It operates in a permissioned mode initially, with a roadmap to decentralization.
• Prover Network: A decentralized network of nodes that generates the zk-SNARK proofs for the sequenced batches. This separation allows the sequencer to be fast while the computationally intensive proving happens in parallel.

To protect users against sequencer censorship or downtime, Scroll implements an escape hatch mechanism. If the sequencer is unresponsive, users can submit a forced transaction request directly to a smart contract on Ethereum L1.

• Process: The user provides a Merkle proof of their assets on L2.
• Safety Net: This ensures users can always retrieve their funds, even in extreme failure scenarios, aligning with Ethereum's self-custody ethos.

Like most new L2s, Scroll's contracts are upgradeable to allow for protocol improvements and bug fixes. This introduces a trust assumption in the upgrade key holders.

• Security Council: Upgrade permissions are managed by a multi-signature wallet controlled by a diverse set of entities.
• Timelocks: Proposed upgrades are subject to a delay, giving users time to exit if they disagree with a change.
• Goal: The roadmap aims to progressively decentralize governance and eventually remove upgradeability.

While the proving network is designed to be decentralized, initial stages may have temporary centralization risks.

• Trusted Setup: Scroll conducted a Perpetual Powers of Tau ceremony for its zk-SNARK circuits, requiring trust in the participants only during the setup phase.
• Prover Incentives: The economic model for provers is crucial for maintaining a robust, decentralized network resistant to censorship.

The official bridge to Scroll is a set of canonical, non-upgradeable contracts deployed on Ethereum and Scroll. This is the most secure way to move assets.

• Native ETH: Scroll uses a wrapped ETH (WETH) design on L2, where ETH is represented by a canonical WETH contract. Bridging mints/burns the token directly.
• Third-Party Bridges: Users should be aware that alternative bridges introduce additional trust assumptions and smart contract risk beyond Scroll's core security model.

A core design goal of Scroll is EVM equivalence, meaning its execution environment is identical to Ethereum's at the bytecode level. This ensures:

• Developer familiarity: No need to learn a new language; existing Solidity/Vyper code works.
• Tooling compatibility: MetaMask, Hardhat, and other Ethereum development tools function seamlessly.
• Security: Inherits the battle-tested security model of the EVM.

The zkEVM is the zero-knowledge proving system that makes Scroll's EVM equivalence possible. It's a complex circuit that generates proofs for general EVM execution. Key types include:

• Type 2 zkEVM (Scroll's approach): Fully EVM-equivalent, matching Ethereum's gas costs and storage layout.
• Type 3 zkEVM: Almost equivalent, with minor deviations for easier proof generation.
• Type 4 zkEVM: Compiles high-level language code directly to a custom IR for proving.

Scroll's network relies on specialized nodes:

• Sequencer: The primary node that receives, orders, and executes transactions, batching them into rollup blocks. It provides low-latency user experiences.
• Prover (or Aggregator): A node that generates the zero-knowledge proof for a batch of transactions. This computationally intensive process is separate from sequencing, allowing for decentralized proving networks.

Moving assets between Ethereum (L1) and Scroll (L2) involves a bridge. Scroll uses a canonical bridge where assets are locked on L1 and minted on L2. Finality has two stages:

• Soft Finality: Instant confirmation on L2 after the sequencer includes your transaction.
• Hard Finality: Occurs when the validity proof for the batch is verified and settled on Ethereum L1, typically taking several minutes.

The main alternative to ZK-Rollups. Optimistic Rollups (like Arbitrum, Optimism) assume transactions are valid and only run computation to prove fraud via a challenge period (usually 7 days). Key differences:

• Security: ZK-Rollups offer cryptographic security; Optimistic rely on economic incentives and watchers.
• Withdrawal Time: ZK-Rollup withdrawals are fast (proven); Optimistic withdrawals are delayed by the challenge period.
• Proving Cost: ZK proofs are computationally expensive to generate but cheap to verify.