StarkNet is a general purpose ZK-Rollup built using STARK cryptographic proof system. StarkNet uses the Cairo programming language both for its infrastructure and for writing StarkNet contracts. L2 <--> L1 messaging infrastructure is available and contracts are fully composable. It is currently launched with a single Sequencer.
Funds can be stolen if
Funds can be lost if
Funds can be frozen if
Users can be censored if
MEV can be extracted if
Each update to the system state must be accompanied by a ZK Proof that ensures that the new state was derived by correctly applying a series of valid user transactions to the previous state. Once the proof is processed on the Ethereum blockchain the L2 block is instantly finalized.
Despite their production use ZK-STARKs proof systems are still relatively new, complex and they rely on the proper implementation of the polynomial constraints used to check validity of the Execution Trace.
Funds can be lost if the proof system is implemented incorrectly.
State diffs are publish on-chain as calldata on every state update. The state diffs contain information on every contact whose storage was updated, and additional information on contract deployments. From diffs full system state can be recovered.
The operator is the only entity that can propose blocks. A live and trustworthy operator is vital to the health of the system. Typically, the Operator is the hot wallet of the StarkNet service submitting state updates for which proofs have been already submitted and verified.
MEV can be extracted if the operator exploits their centralized position and frontruns user transactions.
There is no general mechanism to force the sequencer to include the transaction.
Users can be censored if the operator refuses to include their transactions.
The user initiates the withdrawal by submitting a transaction on L2. When the block containing that transaction is proven the funds become available for withdrawal on L1. Finally the user submits an L1 transaction to claim the funds. This transaction does not require a merkle proof. Note that the withdrawal request can be censored by the Sequencer.
Funds can be frozen if the operator censors withdrawal transaction.
There is no generic escape hatch mechanism as StarkNet cannot be frozen. Application developers can develp app-specific escape hatches that could allow users to exit funds when L2 app is frozen. Note that freezing mechanizm on L2, to be secure, requires anti-censorship protection.
The system uses the following set of permissioned addresses:
Can upgrade implementation of the system, potentially gaining access to all funds stored in the bridge. Can also upgrade implementation of SHARP Verifier, potentially with code approving fraudulent state. Currently there is no delay before the upgrade, so the users will not have time to migrate.
Can upgrade implementation of the StarknetCore contract, potentially allowing fraudulent state to be posted.
Allowed to post state updates. When the operator is down the state cannot be updated.
In DAI bridge it can set max deposit per bridge and per user. In DAI escrow it can approve token transfers.
The system consists of the following smart contracts:
Starkware SHARP verifier used collectively by StarkNet, Sorare, Immutable X and rhino.fi. It receives STARK proofs from the Prover attesting to the integrity of the Execution Trace of these four Programs including correctly computed L2 state root which is part of the Program Output.
MemoryPageFactRegistry is one of the many contracts used by SHARP verifier. This one is important as it registers all necessary on-chain data such as StarkNet contracts state diffs.
Custom DAI Gateway, main entry point for users depositing DAI to L2 where "canonical" L2 DAI token managed by MakerDAO will be minted. Managed by MakerDAO.
DAI Vault for custom DAI Gateway managed by MakerDAO. This contract stores the following tokens: DAI.
The current deployment carries some associated risks:
Funds can be stolen if a contract receives a malicious code upgrade. There is no delay on code upgrades (CRITICAL).