Polygon announces zkEVM – the “final solution” for scaling Ethereum and the smart contract ecosystem. Is that just a marketing phrase – or really the promised breakthrough? A close look at what makes zkEVM special.
In a dynamic market, people like to say that you should do everything you can to get rid of yourself before the others do it. Polygon, the developers of the Ethereum sidechain of the same name, seem to take this advice to heart. Instead of resting on the laurels of the remarkable success of the blockchain Polygon (Matic) , they are working on better scaling solutions that make them redundant.
On March 27th, the company proudly announces that Polygon zkEVM will go live on the Ethereum mainnet after all tests were successful. This will “start a revolution” and “unlock mass adoption and the full potential of Web3.”
Can’t get any smaller. zkEVM is intended to be the final solution for scaling blockchains. The final game. That’s the promise. Everything before zkEVM was just a prelude, including its own blockchain.
Is that really the case? And what’s behind it?
Rollups scale Ethereum
First off, Polygon zkEVM is a “ rollup ”. Rollups have emerged as the preferred scaling solution on the Ethereum scene. A rollup collects transactions and then only publishes the results on the blockchain. This reduces the need for space by a factor of 100 or 1000 without sacrificing the user experience, like the Lightning network does for Bitcoin.
That sounds good, but doesn’t explain why Polygon’s zkEVM is a milestone. Because there are already rollups and, as the L2beat.com site shows, they are in active use. Arbitrum and Optimism are the top two of more than 10 rollups that combined have been handling significantly more transactions than the Ethereum mainchain itself since October. Scaling through rollups hasn’t waited for Polygon.
So if zkEVM didn’t invent the rollups – why should it be a breakthrough? And why does not only Polygon say that, but also some from the scene?
Optimistic Rollups and their mistakes
The answer is a bit complicated. Basically, most agree that while Arbitrum and Optimism are good, they’re not the complete solution yet. These two leading rollups are so-called “Optimistic Rollups”.
Without going into too much detail, Optimistic Rollups introduce a central party—the server that collects the transactions and publishes the results—and that party requires some trust. The smart contract is indeed constructed in such a way that it cannot really cheat. But the transactions are only really finalized after at least a week.
This is especially problematic if you lead tokens from the main chain to the rollup or vice versa. Because nobody wants to wait that long, this is where “liquidity providers” usually come into play. This introduces middlemen and risks, and – that would be a next problem – only works well with liquid tokens and not at all with NFTs, for example.
Almost everyone in the Ethereum ecosystem therefore finds that ZK rollups like zkEVM are the clearly better solution.
Zero Knowledge Proof
The ZK in ZK-Rollup stands for “Zero Knowledge Proof”. It means a cryptographic method to prove something without revealing it.
The Zero Knowledge Proofs have been present in the crypto market for several years, especially where privacy is concerned: Zcash uses them, for example, to prove that a “Shielded Transaction” is valid without disclosing the link to the sender; Confidential Transactions at Monero prove that a transaction only spends the amount of coins the sender owns without revealing the amount; and the mixer Tornado.Cash uses them to prove that an address has the right to withdraw something from a pool without revealing which address it used to deposit something.
With the rollups , zero knowledge proofs come into play when a distillate of the transactions in the rollup is placed on the Ethereum blockchain: they prove that the distillate is valid without revealing the underlying source – the transactions. The proof is so much shorter than the material, and it is verified just like any other operation on Ethereum. This makes the validity of the rollup part of the consensus! No trust is required and the transaction is finalized in just a few minutes.
It is also claimed that ZK-Rollups can scale further than Optimistic Rollups, but I cannot understand or verify this.
But that still doesn’t explain why Polygon’s zkEVM should be such big news. Because one more question remains open.
The full compatibility
There are already a number of ZK rollups that are already being used. At L2Beat we can find several ZK rollups based on StarkEx pushing a respectable volume, such as dYdX, ImmutableX, ApeX, Sorare and others. So why is Polygon’s zkEVM a game changer with such fierce competition?
The answer is that zkEVM replicates the complete Ethereum Virtual Machine (EVM) . The rollups based on StarkEx, on the other hand, only cover specific purposes – switching, NFTs, specific tokens. With zkEVM, on the other hand, everything that works on Ethereum is possible. And that’s the big breakthrough, says Polygon.
“The general consensus was that it would be years before we would get EVM equivalent zkEVMs. Therefore, the Ethereum community was content with compromises.” Mapping the EVM in a way that can be used in a ZK rollup is a tough, tedious task, but Polygon accomplished it with zkEVM sooner than anyone expected, and ahead of its competitors like zkSync or Scroll. Polygon boasts that this makes zkEVM the “gold standard”. First of all, developers can copy everything that runs on Ethereum without modification and make it work in a ZK rollup. It really is the first of its kind!
In addition, there is another, perhaps even more decisive advantage.
Sequencers and Aggregators
The zkEVM has a decentralized structure. The previously usual Optimistic Rollups revolve around a central middleman, just like the functional StarkEx Rollups. Thanks to a smart contract, it cannot cheat, but it can fail. It would be better if you didn’t need it, not least because it makes interoperability more difficult.
zkEVM, on the other hand, is based on a decentralized architecture in which anyone can participate as a “sequencer” or “aggregator” to collect transactions or store their distillate on the blockchain. For this, Polygon uses the self-developed “Proof of Efficiency” consensus algorithm, PoE for short.
The sequencers and aggregators also get a reward for their work – in the form of MATIC, the native tokens of the Polygon blockchain. However, these have no function in the transaction itself. Smart contract fees will continue to be paid in Ether (ETH).
With that, zkEVM actually represents a notable advance over the existing rollups. But does this really justify talking about a “breakthrough”, a “revolution” and the “endgame”? Or are the solutions available so far simply good enough that the market has no need for anything new? Time will tell. However, it is clear that the scaling of Ethereum will not fail due to a lack of options.