zkSync Lite (formerly zkSync) is a user-centric zk rollup platform from Matter Labs. It is a scaling solution for Ethereum, already live on Ethereum mainnet. It supports payments, token swaps and NFT minting.
ZK-SNARKS are zero knowledge proofs that ensure state correctness, but require trusted setup.
All of the data needed for proof construction is published on chain.
There is 21d for upgrades initiated by ZkSync Multisig. The 9 of 15 Security Council can override the delay and allow instant upgrade. Some system components can be changed with no delay but that do not impede the ability for users to withdraw permissionlessly.
Users can force the sequencer to include a withdrawal transaction by submitting a request through L1. If the sequencer censors or is down for for more than 14d, users can use the exit hatch to withdraw their funds.
Users are able to trustlessly exit by submitting a zero knowledge proof of funds.
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. These proofs are then verified on Ethereum by a smart contract.
Despite their production use ZK-SNARKs are still new and experimental cryptography. Cryptography has made a lot of advancements in the recent years but all cryptographic solutions rely on time to prove their security. In addition ZK-SNARKs require a trusted setup to operate.
Funds can be stolen if the cryptography is broken or implemented incorrectly.
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.
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.
Force exit allows the users to escape censorship by withdrawing their funds. The system allows users to force the withdrawal of funds by submitting a request directly to the contract on-chain. The request must be served within a defined time period. If this does not happen, the system will halt regular operation and permit trustless withdrawal of funds.
Users can be censored if the operator refuses to include their transactions. However, there exists a mechanism to independently exit the system.
The user initiates the withdrawal by submitting a regular transaction on this chain. 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.
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. Once the force operation is submitted and if the request is serviced, the operation follows the flow of a regular exit.
If enough time passes and the forced exit is still ignored the user can put the system into Exodus Mode, disallowing further state updates. In that case everybody can withdraw by submitting a zero knowledge proof of their funds with their L1 transaction.
Funds can be lost if the user is unable to generate the non-trivial zk proof for exodus withdraw.
This Multisig is the owner of Upgrade Gatekeeper contract and therefore is allowed to perform upgrades for Governance, Verifier and ZkSync contracts. It can also change the list of active validators and appoint the security council (by upgrading the ZkSync contract). This is a Gnosis Safe with 4 / 8 threshold.
The Security Council’s only role is to reduce the upgrade delay to zero if 9 of its members decide to do so. The council has 15 members which are hardcoded into the ZkSync contract. Changing the council requires a ZkSync contract upgrade.
Those actors are allowed to propose, revert and execute L2 blocks on L1.
Account receiving fees for listing tokens. Can be updated by ZkSync Multisig.
The main Rollup contract. Allows the operator to commit blocks, provide zkProofs (validated by the Verifier) and processes withdrawals by executing blocks. Users can deposit ETH and ERC20 tokens. This contract also defines the upgrade process for all the other contracts by enforcing an upgrade delay and employing the Security Council which can shorten upgrade times. This contract can store any token.
Can be upgraded by: ZkSync Multisig
Upgrade delay: 21d or 0 if overridden by 9 of 15 Security Council
This is the contract that owns Governance, Verifier and ZkSync and facilitates their upgrades. The upgrade constraints are defined by the ZkSync contract.
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).