Polygon Exploring Use of ZK Technology for Main Chain, Co-Founder Bjelic Says

Polygon, an Ethereum scaling project, is exploring ways to bring “zero knowledge,” or ZK, technology – seen by many experts as a major advancement in cryptography’s use in blockchains – to its main chain.

The effort is in addition to Polygon’s ongoing and previously disclosed plans to release a “ZK rollup” – a type of layer 2 scaling system that aims to increase the speed of blockchain transactions and reduce their cost.

Mihailo Bjelic, Polygon’s co-founder, disclosed the exploratory work in an interview with CoinDesk, underscoring just how crucial ZK technology has become for the project's development road map. He said that some ZK-based enhancements could eventually be made to Polygon’s main proof-of-stake (POS) chain – a sidechain off Ethereum – as a way of improving transaction security.

By exploring how ZK technology can be integrated into Polygon’s mainchain, the blockchain is betting big that this scaling technique could drive its ecosystem.

“One of the things that we are experimenting with is upgrading the Polygon POS chain to become ZK-secure, so as to include the zkEVM into the Polygon POS chain itself,” Bjelic said in an interview with CoinDesk.

Read more: What Are Rollups? ZK Rollups and Optimistic Rollups Explained

The development is notable partly because Polygon has successfully attracted big corporate partners in recent years, lured by its fast and cheap transactions and marketing prowess. Meta Platforms announced in May that it will be supporting non-fungible tokens (NFT) from Polygon on Instagram, and investment-management giant Hamilton Lane opened the first of three "tokenized" funds on Polygon earlier this month.

Polygon's native MATIC token tumbled 70% last year in sync with the plunge in broader digital-asset markets. But the price has rebounded 70% already in 2023, or twice as much as the benchmark CoinDesk Market Index.

Polygon's ZK rollup, zkEVM

ZK rollups are a type of scaling system that processes transactions faster on the layer 2, or companion system, of a blockchain, then transporting the transaction data back to the mainnet blockchain – in this case Ethereum, which has been plagued at times in recent years with congestion and elevated fee rates. ZK rollups use “proofs” to show that a transaction is valid by only sharing a small amount of information about that transaction.

In October, Polygon released its zkEVM testnet, which deploys the Ethereum Virtual Machine (EVM) for its ZK rollup, meaning Ethereum developers won’t have to use new programming languages and can move over their smart contracts from the main blockchain without any hiccups. Polygon has not set a date for the release of its ZK rollup, other than to previously say it would happen in early 2023.

When released, the zkEVM will live on a separate chain, meaning that the Polygon POS chain will continue to be a sidechain. Sidechains are less secure than ZK rollups, since they don’t inherit the underlying same security from the main Ethereum blockchain.

“POS chain continues to exist and operate the way it does today. And the Polygon zkEVM will be a separate network,” Bjelic said. “We will have two networks running in parallel, with different value propositions, i.e., features and tradeoffs. Each application will be able to decide which level of security, scalability, and transaction fees they prefer, and basically choose the network accordingly.”

The difference between the two chains would be related to the level of security or the transaction throughput and fees that decentralized applications (dapps) would like to make use of.

The ZK rollup would store its transaction data on Ethereum, and completely derive its security from Ethereum, but the tradeoff is that the throughput is smaller, and transaction fees are more expensive. Crypto analysts have made the point that ZK technology can be computationally intensive, possibly even requiring dedicated “ZK acceleration hardware.”

If the Polygon POS becomes ZK-compatible, it would effectively become what’s known as a validium, which uses proofs like in ZK rollups to ensure that transactions aren’t spoofed with. Unlike a ZK rollup, it doesn’t store data on Ethereum, but off-chain on a separate network.

The validium on Polygon could allow for more transactions to be processed and at lower transaction fees, though it wouldn’t submit the transaction data to Ethereum, instead storing the data off-chain, which is considered less secure.

“This year is going to be very important for Polygon in terms of technology because we will be communicating several major tech milestones and upgrades,” Bjelic told CoinDesk.

Read more: Ethereum Scaling Tool Polygon Launches its zkEVM Public Testnet