Security Mechanisms and Protocols

zkSync employs a multi-faceted security approach to ensure the integrity and reliability of its Layer 2 scaling solution. The use of zero-knowledge rollups (zkRollups), which bundle multiple transactions off-chain and then post a single cryptographic proof on-chain, known as a zk-SNARK (Zero-Knowledge Succinct Non-Interactive Argument of Knowledge), guarantees the validity of all transactions in the batch without revealing specific details about them.

Every transaction processed by zkSync is accompanied by a validity proof, that is verified by a smart contract on the Ethereum mainnet. These cryptographic proofs ensure that no single validator can alter the system’s state incorrectly or misappropriate user funds. This method provides a high level of security equivalent to the main Ethereum chain.

In cases where validators become unresponsive or act maliciously, zkSync uses a priority queue mechanism where users can submit exit requests directly to the Ethereum mainnet. Validators are then required to process these requests within a specified timeframe, and if they fail to do so, the system enters exodus mode, allowing users to withdraw their assets directly to the Ethereum mainnet. This mechanism ensures that users retain control over their assets, even in adverse conditions.

zkSync includes a contract upgrade mechanism to facilitate iterative improvements. Users have the right to opt-out of future upgrades if they disagree with proposed changes. A four-week timelock period is provided, during which users can exit the system if they prefer the current state over the new one. This mechanism balances the need for upgrades with user autonomy and security.

The network relies on well-established cryptographic primitives, through a protocol that uses PLONK and RedShift for its proof systems, SHA256 and Rescue for hashing, and muSig for signatures. These components are based on widely accepted cryptographic assumptions, such as collision resistance and pseudo-randomness, ensuring the protocol’s strenghts.

Trustless Operations in zkSync

zkSync’s architecture ensures trustless operations by minimizing the need for users to trust any central authority or validator. This is achieved through the following design principles:

• Cryptographic Guarantees: The use of zk-SNARKs ensures that all transactions are cryptographically verified. Validators cannot alter the system’s state or steal funds because the validity proofs guarantee the correctness of state transitions, making zkSync a trustless system.
• User Control Over Funds: zkSync’s design allows users to retain control over their funds at all times. Private keys can be stored in cold storage, and users do not need to actively monitor the network. Even in the event of validator failures, users can withdraw their assets directly to the Ethereum mainnet using the priority queue system.
• Decentralized Security Council: The upgrade mechanism is overseen by a security council consisting of well-known members of the Ethereum community. This council can approve urgent upgrades by a supermajority vote, ensuring that security patches can be applied swiftly while maintaining a decentralized governance structure.

Privacy Enhancements in zkSync

zkSync enhances privacy through the use of zero-knowledge proofs, which allow transactions to be validated without revealing any specific details about the transactions themselves. It also supports confidential smart contracts that can execute logic without exposing the underlying data. This is very meaningful, especially for applications that require privacy, such as confidential financial transactions or private data management.

Comparison with Other Privacy Solutions:

zkSync’s privacy features are compared to other Layer 2 solutions and privacy-focused blockchains:

• Optimistic Rollups: Unlike zk-Rollups, Optimistic Rollups rely on a fraud-proof mechanism where transactions are assumed valid unless challenged. This model requires on-chain data availability and does not inherently provide privacy for transaction details. zk-Rollups, on the other hand, provide instant validity proofs without revealing transaction details, offering superior privacy.
• Privacy Coins: Privacy-focused cryptocurrencies like Monero and Zcash provide on-chain privacy through advanced cryptographic techniques such as ring signatures and zk-SNARKs. While these solutions offer strong privacy guarantees, they do not address scalability as effectively as zk-Rollups. zkSync combines privacy with scalability, making it suitable for high-throughput applications.
• Other Layer 2 Solutions: Compared to other Layer 2 solutions like Polygon and Arbitrum, zkSync offers superior privacy due to its use of zero-knowledge proofs. While these solutions improve scalability, they do not inherently provide the same level of transaction privacy as zkSync.

Audits and Bug Bounty Programs

Security Audits and Results

zkSync has undergone multiple security audits to ensure its protocol is secure and reliable. These audits are conducted by reputable security firms specializing in blockchain technology, and cover a number of important aspects of the protocol, including cryptographic assumptions, smart contract code, and system architecture.

The audit process involves a thorough examination of the zkSync protocol to identify potential vulnerabilities. This includes static and dynamic analysis of the codebase, formal verification of cryptographic protocols, and stress testing under various scenarios. The goal is to ensure that the protocol can withstand attacks and function correctly under different conditions.

Results have generally been positive, with no critical vulnerabilities found. Minor issues identified during the audits were promptly addressed by the zkSync development team. The continuous auditing process helps maintain the protocol’s security as it evolves.

Bug Bounty Programs and Community Contributions

zkSync operates an active bug bounty program to incentivize the discovery and reporting of security vulnerabilities. This program invites security researchers and developers from the community to identify and report bugs in exchange for financial rewards. Their tiered rewards are based on the severity of the reported vulnerabilities. For instance, issues receive higher rewards, incentivizing researchers to focus on identifying significant security flaws, though a structure that ensures that the most serious vulnerabilities are prioritized and addressed promptly.

Besides the bug bounty program, zkSync has also established a security council with well-known members of the Ethereum community, to oversee the protocol’s security. They can approve urgent upgrades to address issues, and the involvement of respected community members in the security council adds a layer of trust and accountability to the protocol’s security framework.

Highlights

• Security Mechanisms: zkSync uses zero-knowledge rollups (zkRollups) where transactions are processed off-chain and verified by zk-SNARKs on Ethereum, ensuring high security.
• Trustless Operations: zkSync employs cryptographic guarantees like validity proofs and a priority queue for emergency exits, ensuring users retain control over their funds.
• Privacy Enhancements: zkSync keeps transaction details private using zero-knowledge proofs, offering superior privacy compared to other solutions like Optimistic Rollups.
• Audits and Bug Bounty Programs: zkSync undergoes extensive security audits and operates a bug bounty program to identify and address vulnerabilities, leveraging community expertise.
• Governance: zkSync’s decentralized governance model allows ZK token holders to vote on protocol changes, with a security council overseeing urgent upgrades to ensure security and transparency.