zkSync Era is a layer 2 rollup that uses zero-knowledge proofs to scale Ethereum without compromising on security or decentralization. Since it's EVM compatible (Solidity/Vyper), 99% of Ethereum projects can redeploy without refactoring or re-auditing a single line of code. zkSync Era also uses an LLVM-based compiler that will eventually let developers write smart contracts in C++, Rust and other popular languages.

To keep the zero-knowledge circuits as simple as possible and enable simple extensions, we created the system contracts. These are privileged special-purpose contracts that instantiate some recurring actions on the protocol level. Some of the most commonly used contracts:

ContractDeployer This contract is used to deploy new smart contracts. Its job is to make sure that the bytecode for each deployed contract is known. This contract also defines the derivation address. Whenever a contract is deployed, a ContractDeployed event is emitted.

L1Messenger This contract is used to send messages from zkSync to Ethereum. For each message sent, the L1MessageSent event is emitted.

NonceHolder This contract stores account nonces. The account nonces are stored in a single place for efficiency (the tx nonce and the deployment nonce are stored in a single place) and also for the ease of the operator.

Bootloader For greater extensibility and to lower the overhead, some parts of the protocol (e.g. account abstraction rules) were moved to an ephemeral contract called a bootloader.

We call it ephemeral because it is not physically deployed and cannot be called, but it has a formal address that is used on msg.sender, when it calls other contracts.

The zkSync Era system-contracts are distributed under the terms of the MIT license.

See LICENSE-MIT for details.

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zkSync Era has been through lots of testing and audits. Although it is live, it is still in alpha state and will go through more audits and bug bounties programs. We would love to hear our community's thoughts and suggestions about it! It is important to state that forking it now can potentially lead to missing important security updates, critical features, and performance improvements.