Blast – L2BEAT

Website	blast.io/en
App	blast.io/en/airdrop/early-access blast.io/en/bridge
Docs	docs.blast.io/about-blast
Explorer	blastscan.io blastexplorer.io
Social	@Blast_L2

4

Milestones

Blast upgrades to censor exploiter

2024 Mar 26th

The Munchables exploiter is prohibited from forcing transactions.

Learn more

Blast Network Launch

2024 Feb 29th

Blast Network is live on mainnet.

Learn more

5

Risk summary

Fraud proof system is currently under development. Users need to trust the block proposer to submit correct L1 state roots.

Fraud proof system is currently under development. Users need to trust the block proposer to submit correct L1 state roots.

Sequencer failureState validationData availabilityExit windowProposer failure

State validation

In development

Currently the system permits invalid state roots. More details in project overview.

Data availability

On chain

All of the data needed for proof construction is published on chain.

Exit window

None

There is no window for users to exit in case of an unwanted upgrade since contracts are instantly upgradable.

Sequencer failure

Self sequence

In the event of a sequencer failure, users can force transactions to be included in the project’s chain by sending them to L1. There is a 12h delay on this operation.

Proposer failure

Cannot withdraw

Only the whitelisted proposers can publish state roots on L1, so in the event of failure the withdrawals are frozen.

7

Rollup stage

Blast is a

Stage 0

Optimistic Rollup.

Stage 0

4 requirements met

Stage 1

3 issues need fixing

Stage 2

1 issue needs fixing

Learn more about Rollup stages

Please keep in mind that these stages do not reflect rollup security, this is an opinionated assessment of rollup maturity based on subjective criteria, created with a goal of incentivizing projects to push toward better decentralization. Each team may have taken different paths to achieve this goal.

8

Technology

Fraud proofs are in development

Ultimately, OP stack chains will use interactive fraud proofs to enforce state correctness. This feature is currently in development and the system permits invalid state roots.

Funds can be stolen if an invalid state root is submitted to the system (CRITICAL).

L2OutputOracle.sol - Etherscan source code, deleteL2Outputs function

All data required for proofs is published on chain

All the data that is used to construct the system state is published on chain in the form of cheap calldata. This ensures that it will always be available when needed.

9

State derivation

Node software

Node software can be found here.

Compression scheme

Data batches are compressed using the zlib algorithm with best compression level.

Genesis state

The genesis file can be found here.

Data format

The format specification of Sequencer’s data batches can be found here.

10

Operator

The system has a centralized operator

The operator is the only entity that can propose blocks. A live and trustworthy operator is vital to the health of the system.

MEV can be extracted if the operator exploits their centralized position and frontruns user transactions.

Users can force any transaction

Because the state of the system is based on transactions submitted on-chain and anyone can submit their transactions there it allows the users to circumvent censorship by interacting with the smart contract directly.

11

Withdrawals

Regular exit

The user initiates the withdrawal by submitting a regular transaction on this chain. When the block containing that transaction is finalized the funds become available for withdrawal on L1. The process of block finalization takes a challenge period of 12d to complete. Once funds are added to the withdrawal queue, operator must ensure there is enough liquidity for withdrawals. If not, they need to reclaim tokens from Yield Providers.

Funds can lose value if there is a hack or the yield goes negative for yield providers (CRITICAL).
Funds can be frozen if there is not enough liquidity in the bridge, transactions are locked in withdrawal queue (CRITICAL).

Forced exit

If the user experiences censorship from the operator with regular exit they can submit their withdrawal requests directly on L1. The system is then obliged to service this request or halt all withdrawals, including forced withdrawals from L1 and regular withdrawals initiated on L2. Once the force operation is submitted and if the request is serviced, the operation follows the flow of a regular exit.

Forced withdrawal from an OP Stack blockchain

12

Other considerations

EVM compatible smart contracts are supported

OP stack chains are pursuing the EVM Equivalence model. No changes to smart contracts are required regardless of the language they are written in, i.e. anything deployed on L1 can be deployed on L2.

Introducing EVM Equivalence

13

Permissions

The system uses the following set of permissioned addresses:

ProxyAdmin 0x3642…E883

Owner of AddressManager. Admin of OptimismPortal, SystemConfig, L2OutputOracle, L1ERC721Bridge, OptimismMintableERC20Factory, L1StandardBridge.

Sequencer 0x415c…4AA7

Central actor allowed to commit L2 transactions to L1.

Proposer 0x082b…A821

Central actor allowed to post new L2 state roots to L1.

Challenger 0x4f72…8B05

Central actor allowed to delete L2 state roots proposed by a Proposer.

Guardian 0x4f72…8B05

Central actor allowed to pause deposits and withdrawals.

BlastMultisig 0x4f72…8B05

This address is the owner of all upgradable contracts. It is also designated as a Guardian of the OptimismPortal, meaning it can halt withdrawals and as a Challenger. It can upgrade the bridge implementation potentially gaining access to all funds, and change the sequencer, state root proposer or any other system component (unlimited upgrade power). This is a Gnosis Safe with 3 / 5 threshold.

BlastMultisig participants 0x6520…39a4 0x480E…1B2C 0xf97e…705d 0xAb59…fADA 0x2cF4…A03d

Those are the participants of the BlastMultisig.

SystemConfig Owner. 0x7c46…f3aF

Account privileged to change System Config parameters such as Sequencer Address and gas limit.

14

Smart contracts

A diagram of the smart contract architecture

The system consists of the following smart contracts:

L2OutputOracle 0x826D…5c76 Implementation (Upgradable)Admin

The L2OutputOracle contract contains a list of proposed state roots which Proposers assert to be a result of block execution. Currently only the PROPOSER address can submit new state roots.