Starknet
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Tokens:
Milestones
StarkGate Alpha
2022 May 9th
Bridge is live on mainnet, serving as gateway between Ethereum and Starknet.
Learn moreStarknet Alpha
2021 Nov 29th
Rollup is live on mainnet, enabling general computation using zkRollup technology.
Learn moreKnowledge Nuggets
Description
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.
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Risk Analysis
State validation
ZK proofs (ST)ZK-STARKS are zero knowledge proofs that ensure state correctness.
Data availability
On chainAll of the data needed for proof construction is published on chain.
Upgradeability
YesThe code that secures the system can be changed arbitrarily and without notice.
Sequencer failure
No mechanismThere is no mechanism to have transactions be included if the sequencer is down or censoring.
Proposer failure
Cannot withdrawOnly the whitelisted proposers can publish L2 state roots on L1, so in the event of failure the withdrawals are frozen.
Technology
Validity proofs ensure state correctness
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.
Zero knowledge STARK cryptography is used
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.
All data required to reconstruct rollup state is published on chain
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.
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. 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.
Users can't force any transaction
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.
Withdrawals
Regular exit
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.
Emergency exit
There is no generic escape hatch mechanism as Starknet cannot be forced by users into a frozen state. Note that a freezing mechanism on L2, to be secure, requires anti-censorship protection.
Permissions
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 the StarknetCore contract, potentially allowing fraudulent state to be posted. Currently there is no delay before the upgrade, so the users will not have time to migrate.
One of Proxy Governors. This is a Gnosis Safe with 2 / 3 threshold.
Those are the participants of the Proxy Multisig.
The governors are responsible for: appointing operators, changing program hash, changing config hash, changing message cancellation delay. There is no delay on governor actions.
Can upgrade implementation of SHARP Verifier, potentially with code approving fraudulent state. Currently there is 28d delay before the upgrade.
SHARP Verifier Governor. This is a Gnosis Safe with 2 / 3 threshold.
Those are the participants of the SHARPVerifierGovernorMultisig.
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.
Can upgrade implementation of the ETH escrow, potentially gaining access to all funds stored in the bridge. Currently there is 7d delay before the upgrade.
Can upgrade implementation of the WBTC escrow, potentially gaining access to all funds stored in the bridge. Currently there is 7d delay before the upgrade.
Can upgrade implementation of the USDC escrow, potentially gaining access to all funds stored in the bridge. Currently there is 7d delay before the upgrade.
Can upgrade implementation of the USDT escrow, potentially gaining access to all funds stored in the bridge. Currently there is 7d delay before the upgrade.
Smart Contracts
The system consists of the following smart contracts:
Starknet contract receives (verified) state roots from the Sequencer, allows users to read L2 -> L1 messages and send L1 -> L2 message.
Can be upgraded by: Starknet Proxy Governors
Upgrade delay: No delay
CallProxy for GpsStatementVerifier.
Starkware SHARP verifier used collectively by Starknet, Sorare, ImmutableX, Apex, Myria, rhino.fi and Canvas Connect. It receives STARK proofs from the Prover attesting to the integrity of the Execution Trace of these Programs including correctly computed L2 state root which is part of the Program Output.
Part of STARK Verifier.
Part of STARK Verifier.
MemoryPageFactRegistry is one of the many contracts used by SHARP verifier. This one is important as it registers all necessary on-chain data.
Part of STARK Verifier.
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.
TVL is calculated based on these smart contracts and tokens:
StarkGate bridge for ETH.
Can be upgraded by: StarkGate ETH owner
Upgrade delay: 7d
DAI Vault for custom DAI Gateway managed by MakerDAO.
StarkGate bridge for WBTC.
Can be upgraded by: StarkGate WBTC owner
Upgrade delay: 7d
StarkGate bridge for USDC.
Can be upgraded by: StarkGate USDC owner
StarkGate bridge for USDT.
Can be upgraded by: StarkGate USDT owner
Upgrade delay: 7d
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).