Why Can zkPorter Outperform Rollup?

DeFi之道

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Another invention by Matter Labs.

Original Title: "Major Breakthrough in Layer 2 Scaling! zkPorter Ends the Zk Rollup vs. Optimistic Rollup Debate"

Original Source: The DeFi Way

A large-scale Layer 2 migration is on the horizon. As protocols shift from the Ethereum base layer to Optimistic Rollup and EVM-compatible zk Rollups, many are hopeful that we can finally make on-chain fees manageable. However, everyone involved in Ethereum scaling knows a "dirty secret": even with Rollups, we might end up back where we started. This is because any actual throughput growth will quickly be swallowed by demand-induced usage.

Rollups can only offer linear increases in network throughput—all data still needs to be propagated to all full nodes. To achieve true scalability, we need exponential growth in throughput.

Therefore, we see this as such a crucial breakthrough. We have designed a system capable of 20,000+ TPS, which offers higher security compared to Optimistic Rollup. More importantly, it will go live on mainnet alongside zkSync 2.0 within 6 months.

1. Why are Rollups Insufficient to Solve the Scalability Issue?

In October 2020, Vitalik announced an Ethereum roadmap centered around Rollups, predicting that if all L1 activities transition to Rollup, Ethereum could achieve around 3000 TPS. This is quickly becoming a reality: both Optimistic and zk Rollups now support EVM compatibility, enabling a rapid, straightforward migration of applications from L1 to L2.

Ethereum is growing at an exponential rate. In the past year, the number of DeFi users has increased from 150,000 to 1.8 million—but gas fees have grown 16x. (The cost of each Uniswap trade has gone from $0.20 to $36)

Why? Because any scalability improvement on a new use case will come with increased financial activity/transactions. Consider the following simultaneous events:

DEX Monthly Trading Volume: $17.2 billion —> $67 billion

DeFi TVL: $700 million —> $80 billion (11000% growth)

Opensea Monthly Sales Volume: $5 million —> $100 million

Compared to the Ethereum mainnet, Optimistic Rollup can only increase scalability by about 25 times, while zk Rollups will increase scalability by about 100 times. Before we feel these scalability gains, we will be back to square one: unbearable gas fees and an Ethereum that is unaffordable for most regular users.

Cryptocurrency is on the verge of going mainstream. In a world with 3.8 billion smartphone users (in contrast, Metamask has only 3 million monthly active users), we need to grow that by 1000 times to cater to what is about to happen. This scalability gap is what drives us to build a new product — zkPorter.

2zkPorter: The Engine for Mass Cryptocurrency Adoption

In zkSync 2.0, the L2 state will be split into two aspects: zk Rollup with on-chain data availability and zkPorter with off-chain data availability.

These two parts are composable and interoperable: contracts and accounts on the zk Rollup side will be able to seamlessly interact with accounts on the zkPorter side, and vice versa. That's right! From the user's perspective, the only noticeable difference will be a 100x reduction in transaction fees for zkPorter accounts.

Imagine this: Uniswap deploys their smart contracts on a zkRollup chain, and retail users on zkPorter can make transactions for <0.03 USD. How is this possible? This is because the majority of Rollup costs come from the cost of posting data on Ethereum.

A zkPorter account can perform thousands of swaps on the Uniswap contract, but only needs to post one update to Ethereum.

The data availability of zkPorter accounts will be secured by zkSync token holders called "Guardians." They will track the state of the zkPorter chain by signing blocks to confirm the data availability of zkPorter accounts. Guardians use zkSync tokens for proof of stake (PoS) participation, so any data unavailability will result in them being penalized (slashed). This provides an economic guarantee for data availability.

It is important to note that the PoS in zkSync is much more secure than PoS in other systems (e.g., sidechains). This is because zkSync Guardians are effectively powerless: they cannot steal funds. They can only halt block production. In this scenario, users can still withdraw their funds.

Each user can freely choose their own security threshold. Any user wishing for all data to be available on-chain can fully settle on the Rollup. However, if you are a fee-sensitive user, you can choose to keep funds on zkPorter. (We expect traders and new users are likely to use zkPorter.)

This unlocks a whole class of applications that are uneconomical on L1 or even traditional Rollup apps. They can now have a home on Ethereum and serve Ethereum users.

zkPorter vs Optimistic Rollup

Thanks to the encryption technology of zero-knowledge proofs, all of this is possible.

Optimistic Rollup cannot achieve this level of scalability like zkPorter.

If the data availability is moved off-chain in Optimistic Rollup, malicious operators would be able to steal all funds in the Rollup with no one able to challenge them.

Furthermore, zkPorter provides a stronger security guarantee compared to Optimistic Rollup. To understand why, let's briefly outline the costs and benefits of a potential attack.

1) Cost of Attack

As of today, the cost to attack Optimistic Rollup via 51% collusion of mining power is less than $70 million (and will be even less when PoS arrives). On the other hand, to make data unavailable in zkPorter, the attacker would have to accumulate 1/3 of the total value of all staked tokens (almost certainly exceeding $70 million).

Furthermore, due to significant slippage the attacker would face when buying tokens (and being unable to buy the staked tokens), the cost of such an attack would be much higher than the cost implied by spot prices.

2) Benefit of Attack

If an attack on Optimistic Rollup is successful, the hacker can steal all funds in the Rollup, greatly increasing the incentive for the attack. In contrast, an attack on zkPorter cannot be directly exploited: if successful, the attacker can only halt block production, not steal user funds.

The difficulty of profiting from a service interruption significantly reduces the incentive for such attacks.

4 Building on zkPorter

zkPorter is coming soon. The Matter Labs team is working hard to deploy it into production within 6 months. Soon, the cake cutting ceremony will begin.

zkPorter will be introduced in our next-generation smart contract platform zkSync 2.0, which will support Solidity. Our goal is to provide a public testnet in May and launch later in the summer.

In the meantime, you can use zkSync 1.x for Layer2 payments (live on mainnet since June 2020). It will support transactions and NFTs in a few weeks.