zkSync Era is an L2 protocol based on the ZK cumulative architecture. All assets are held in a smart contract on the main chain (on-chain), while computations and storage occur off-chain. The fundamental concept is that instead of individually verifying each transaction, these transactions are "rolled up" into a single block (rollup block), which is then verified and approved as a whole.

Transaction Finality

Transactions in zkSync Era achieve finality on the Ethereum blockchain once a SNARK proof of the zkSync Era block has been generated and accepted by the smart contract. It is expected that the generation of this proof will take approximately 10 minutes. After this time, the zkSync Era transaction is considered as equally final as any transaction on the Ethereum blockchain included in the same block. When submitting a transaction to the zkSync Era network, there is a wait for the block to be filled, and therefore, the proof is not created immediately. With the higher throughput of the zkSync Era system, the time between blocks is shortened. Although the time until final confirmation takes approximately 10 minutes, this does not impact the usability of the network. Transactions sent to zkSync Era are immediately confirmed to users, appearing instantly to recipients in the user interface and API (even though they are marked as unconfirmed), and the received assets can be immediately used for further transfers (which can even end up in the same zkSync Era block).

Currently (as of May 29, 2023), instant confirmations are only statements from zkSync Era that they will include your transaction in the next block.

Security

The zkSync Era protocol offers cryptographic assumptions and security features that provide users with security guarantees. Users don't need to monitor the network, and their private keys can be kept safe. Validators have no ability to steal funds or disrupt the zkSync Era state. Users can withdraw their assets back to the Ethereum mainnet at any time without the need for cooperation from zkSync Era validators.

Several mechanisms are utilized to achieve these guarantees. The zkSync Era protocol is built on the ZK-rollup architecture, which verifies each transaction through a smart contract on the Ethereum mainnet using a proof of block validity. This prevents system tampering by validators or loss of user funds.

If validators become unavailable, there is an emergency exit mechanism in place. In such a situation, users can submit an exit request directly to the priority queue on the mainnet. Validators are obliged to process these requests within a short time window, but if they fail to do so, the system enters an exodus mode, allowing users to immediately exit zkSync Era and transfer their assets back to the Ethereum mainnet through a direct transaction.

zkPorter

zkPorter is an innovative solution that provides high data availability off-chain for zkSync Era and offers advantages in scalability and transaction fees. Key transaction data necessary for state reconstruction is not directly stored on Ethereum but remains accessible through a Proof of Stake (PoS) mechanism, where stakers represent future holders of the zkSync coin. This approach enables much higher scalability with a capacity of tens of thousands of transactions per second. As a result, transaction fees are significantly reduced to a level comparable to side chains, costing just a few cents.

In terms of safety, zkPorter should offer a higher level of security than any other main or side chain. In the event that a malicious actor controls both the sequencer and more than two thirds of the total stake, they could sign a valid state transition, but would not be able to access the data. In such a scenario, the state would be "frozen," and users would not be able to withdraw their assets, but the attacker's deposit would also be frozen. This means that an attacker with a high stake would not derive any direct financial benefit from exploiting the system. This security mechanism ensures asset protection and minimizes the risk of financial loss in the event of an attack.

Upgrade Mechanism

This is part of the zkSync 1.0 protocol and allows for fast design iterations. However, users have the right to reject future upgrades, as anything new must be announced through the zkSync contract, and users are then given a 4-week time window to exit the protocol if they wish to do so.

The Security Council, which consists of 15 members from the Ethereum community, has the ability to shorten the 4-week time window to ensure a balance between security and upgrade. If Matter Labs initiates an upgrade, at least 9 out of the 15 council members can implement it immediately. In this phase of zkSync Era, a higher probability of errors is expected, which is why this mechanism has been chosen.

Hyperscaling

Fractal Scaling is a smart way to create a heterogeneous, yet highly scalable blockchain system, thanks to the utilization of Zero-Knowledge Proofs (ZKP). Within this concept, multiple ZKP chains run in parallel, known as hyperchains in the zkSync Era world. The block proofs from these hyperchains are then aggregated into a single final block, which is settled on L1 (the main chain). Each of these hyperchains can be a system on its own, and can have an infinite number of additional hyperchains above it, such as L3, L4, and so on. This approach achieves an incredible level of scalability and flexibility for the entire system.

Fractal scaling is important, but it alone is not sufficient to achieve hyperscaling; there is another key component which is necessary. Fractal scaling can always be connected through native bridges via underlying layers, but this creates a central bottleneck for scalability and limits inexpensive direct transfers between users on both chains.

Hyperchain

Hyperchains are parallel running fractal instances of zkEVM that settle on the main L1 mainnet. Anyone can create and deploy hyperchains without permission; however, to maintain trustworthiness and full interoperability, every hyperchain must use the exact same zkEVM engine as the main zkSync Era L2 instance. This ensures that all ZKP circuits remain 100% identical, and that hyperchains inherit security and trustworthiness from L1, regardless of who deployed them. This guarantees zero reliance on trust or security.

This hyperscaling interface, known as hyperchains, is not limited to usage within the zkSync Era chain. To facilitate and expand its usage, the Hyperchain SDK has been developed, which is a set of tools that allows developers to create and deploy their own hyperchains outside the zkSync Era environment.

Hyperbridge

Hyperbridge is a tool that enables asset transfers between different hyperchains with minimal costs and without the need to traverse the layers of individual chains. Similar to hyperlinks on web pages that allow one-click navigation from one page to another, hyperbridges facilitate easy asset transfers between hyperchains.

Smart contracts can utilize hyperbridges for the secure sending of assets and messages between hyperchains without the need for trust. Communication through hyperbridges is always asynchronous. The sending hyperchain must finalize its state up to the oldest common hyperchain, which serves as the foundation for both the sending and receiving hyperchains. Communication latency through hyperbridges is usually a matter of seconds, as hyperchains are capable of generating blocks quickly, and hardware acceleration ensures fast block proof generation.

A zero-knowledge proof is a method by which something can be demonstrated as true without directly revealing the information. One person, called the prover, attempts to prove a statement, while another person, the verifier, is responsible for verifying if the statement is indeed true.

Zero-knowledge proofs have undergone significant development in recent years, offering new possibilities for anonymizing data flows on the blockchain. This makes it more difficult to link an address to a specific individual and track their movements.

An example showcasing the power of zero-knowledge proof technology is a decentralized application (dApp) on the Ethereum blockchain called Tornado Cash. This application utilizes zero-knowledge proofs to secure and mask your transactional activities when using the app.

It is important to note that zero-knowledge proof technology brings not only benefits, but can also raise concerns regarding illegal activities. One of the main drawbacks of zero-knowledge proofs is the creation of a shared reference chain that is available to all participating contributors. Unfortunately, users cannot independently assess whether all participants are genuinely honest.

Nevertheless, I believe that the development of zero-knowledge proof technologies represents an important step towards enhancing privacy and protecting user data on the blockchain. The future of zero-knowledge proofs promises even greater advancements in privacy protection and ensuring anonymity in financial transactions and data sharing on public blockchain networks.