Scroll Upgrades

As the team continues to progress on Scroll’s roadmap, we will be upgrading the Scroll network to include new features and improvements.

The following contracts are used to initiate upgrades and execute upgrades after the two-week timelock period:

You can join our Telegram channel for technical updates, which includes future upgrade announcements and on-chain operation events.

Curie Upgrade

Overview

This significant upgrade will reduce gas fees on the Scroll chain by 1.5x. Highlights include:

• Compresses the data stored in blobs using the zstd algorithm. This compression reduces the data size, allowing each blob to store more transactions, thereby reducing data availability cost per transaction.
• Adopts a modified version of the EIP-1559 pricing model which is compatible with the EIP-1559 transaction interface, bringing beneftis such as more accurate transaction pricing and a more predictable and stable fee structure.
• Support for new EVM opcodes TLOAD, TSTORE, and MCOPY. Users can safely use the latest Solidity compiler version 0.8.26 to build the contracts.
• Introduces a dynamic block time. During periods of traffic congestion, a block will be packed when the number of transactions reaches the circuit limit instead of waiting for the 3-second interval.

Timeline

• Scroll Sepolia
  • Network Upgrade: June 17th, 2024
• Scroll Mainnet
  • Upgrade Initiation: June 20th, 2024
  • Timelock Completion & Upgrade: July 3rd, 2024

Technical Details

Contract Changes

The code changes for this upgrade are documented in the following PRs:

• Accept compressed batches
• Update L1GasPriceOracle
• Change MAX_COMMIT_SCALAR and MAX_BLOB_SCALAR to 1e18
• Remove batch index check when updating a verifier

The main changes are as follows:

• The rollup contract (ScrollChain) will now accept batches with both versions 1 and 2. Version 1 is used for uncompressed blobs (pre-Curie), while version 2 is used for compressed blobs (post-Curie).
• The L1GasPriceOracle contract will be updated to change the data fee formula to account for blob DA, providing a more accurate estimation of DA costs:
  • Original formula: (l1GasUsed(txRlp) + overhead) * l1BaseFee * scalar
  • New formula: l1BaseFee * commitScalar + len(txRlp) * l1BlobBaseFee * blobScalar

Node Changes

The new node version is v5.5.0. See the release notes for the list of changes.

zkEVM circuit changes

The new version of zkevm circuits is v0.11.4. See here for the release log.

Audits

• TrailofBits: coming soon!
• Zellic

Compatibility

Sequencer and Follower Nodes (l2geth)

This upgrade is a hard fork, introducing the TLOAD, TSTORE, and MCOPY opcodes. Operators running an l2geth node are required to upgrade before the hard fork block. For more information, see the node release note.

Dapps and Indexers

For dApps, this upgrade is backward compatible. Developers should adjust the gas fee settings to incorporate the EIP-1559 pricing model. Note that dApps can no longer rely on the fixed 3-second block time in the application logic.

For indexers, the data format remains the same. The will be however changes to the data content:

• The version field in BatchHeader will be changed to 2 since Curie block.
• The data stored in blob will be compressed and can be decompressed by zstd v1.5.6.

Bernoulli Upgrade

Overview

This upgrade features a significant reduction in transaction costs by introducing support for EIP-4844 data blobs and supporting the SHA2-256 precompile.

Timeline

• Scroll Sepolia
  • Network Upgrade: April 15th, 2024
• Scroll Mainnet
  • Upgrade Initiation: April 15th, 2024
  • Timelock Completion & Upgrade: April 29th, 2024

Technical Details

Contract changes

The contract changes for this upgrade are in this PR, along with the audit fixes here. The main changes are as follows:

• ScrollChain now accepts batches with either calldata or blob encoding in commitBatch.
• ScrollChain now supports finalizing blob-encoded batches through finalizeBatchWithProof4844.
• MultipleVersionRollupVerifier can now manage different on-chain verifiers for each batch encoding version.

Node changes

The new node version is v5.3.0. See here for the release log.

zkEVM circuit changes

The new version of zkevm circuits is v0.10.3. See here for the release log.

Audits

• OpenZeppelin
• TrailofBits

Compatibility

Sequencer and follower nodes (l2geth)

This upgrade is a hard fork as it introduces the new blob data type and the SHA2-256 precompiled contract. Operators running an l2geth node are required to upgrade before the hard fork block. See the node releases for more information.

Indexers and Bridges

This upgrade changes the format that Scroll uses to publish data to Ethereum. Projects that rely on this data should carefully review the new data format, and check whether their decoders need to be adjusted. A summary of the new format:

• The format of BlockContext will not change.
• Chunks will no longer include the L2 transaction data. This will instead be stored in a blob attached to the commitBatch transaction.
• BatchHeader now contains one new field, BlobVersionedHash.

Provers

This upgrade involves a breaking change in zkevm-circuits. Operators running a prover node are required to upgrade.

Bridge Upgrade

Overview

To reduce bridging costs, we implemented several gas optimizations on our bridge and rollup contract suite. The optimization techniques used include the following:

• We will now use constants to store some companion contract addresses, instead of using storage variables. This is possible since these values should (almost) never change. With this change we can save on a few storage load operations.
• We updated the intrinsic gas estimation in L1MessageQueue to use a simple upper bound instead of an exact calculation. The two results will be similar for most bridge transactions but the new implementation is significantly cheaper.
• We merged two contracts L1MessageQueue and L2GasPriceOracle to save on call costs from one contract to the other.

Timeline

• Scroll Sepolia:
  • Network Upgrade: January 19, 2024
• Scroll Mainnet:
  • Upgrade Initiation: February 7, 2024
  • Timelock Completion & Upgrade: February 21, 2024

Technical Details

Code Changes

• Bridge Cost Optimization
• Audit Fixes
• Previously deployed version (commit ff380141a8cbcc214dc65f17ffa44faf4be646b6)
• Version deployed (commit 6030927680a92d0285c2c13e6bb27ed27d1f32d1)

Audits

• OpenZeppelin

List of Changes

Changes to L1 contracts:

• In ScrollChain, change messageQueue and verifier to immutable.
• In L1ScrollMessenger, change counterpart, rollup, and messageQueue to immutable.
• In all token gateways, change counterpart, router, and messenger to immutable.
• Merge L1MessageQueue and L2GasPriceOracle into a single contract L1MessageQueueWithGasPriceOracle (deployed on the same address as the previous L1MessageQueue). In this contract, we also change messenger and scrollChain to immutable, and simplify calculateIntrinsicGasFee.

Changes to L2 contracts:

• In L2ScrollMessenger, change counterpart to immutable.
• In all token gateways, change counterpart, router, and messenger to immutable.

Contracts affected:

• L1: L1MessageQueue, L2GasPriceOracle, ScrollChain, L1WETHGateway, L1StandardERC20Gateway, L1GatewayRouter, L1ScrollMessenger, L1CustomERC20Gateway, L1ERC721Gateway, L1ERC1155Gateway.
• L2: L2ScrollMessenger, L2WETHGateway, L2StandardERC20Gateway, L2GatewayRouter, L2CustomERC20Gateway, L2ERC721Gateway, L2ERC1155Gateway.

Compatibility

Sequencer and follower nodes (l2geth)

Operators running an l2geth node do not need to upgrade. The changes in this upgrade will not affect l2geth.

Dapps and indexers

Dapps and indexers (and similar off-chain infrastructure) that query contracts or rely on contract interfaces would, in most cases, not need to be changed. The majority of the contract changes are internal and/or backward compatible.

If your application depends on L2GasPriceOracle to monitor how Scroll keeps track of the L2 gas price on L1, from the upgrade block number you will need to start monitoring L1MessageQueueWithGasPriceOracle.

The original gas price oracle contract will be deprecated: it will no longer be updated or used by the Scroll bridge.

• Ethereum:
  • L2GasPriceOracle: 0x987e300fDfb06093859358522a79098848C33852
  • L1MessageQueueWithGasPriceOracle: 0x0d7E906BD9cAFa154b048cFa766Cc1E54E39AF9B
• Sepolia:
  • L2GasPriceOracle: 0x247969F4fad93a33d4826046bc3eAE0D36BdE548
  • L1MessageQueueWithGasPriceOracle: 0xF0B2293F5D834eAe920c6974D50957A1732de763