Motion: ZK rollup has a better set of security/scalability tradeoff than optimistic rollup (Alex Gluchowski vs. John Adler, co-host: James Prestwich)

The Blockchain Debate Podcast

Guests:
Alex Gluchowski (@gluk64)
John Adler (@jadler0)
Host:
Richard Yan (@gentso09)
James Prestwich (@_prestwich, special co-host)

Today’s motion is “ZK rollup has a better set of security/scalability tradeoff than Optimistic rollup.”
Rollups are a class of layer-2 Ethereum scalability solutions. They allow an off-chain aggregation of transactions inside a smart contract. Users can transact inside the contract with security guarantees, and they will settle to the mainchain at some future point.
ZK and optimistic rollups are different in the way they ensure the validity of these transactions that are being kept off-chain.
The ZK approach uses math. It bundles the transactions, compresses them, and adds a zero-knowledge proof that indicates the validity of the state transitions. When the transaction is sent to the mainchain, the block is verified by the attached zero-knowledge proof.
The optimistic approach uses economic incentives. An operator publishes a state root that isn’t constantly checked by the rollup smart contract. Instead, everybody hopes that the state transition is correct. However, other operators or users can challenge the validity of the transactions, revert the incorrect block, and slash malicious operators.
We compared the two approaches from the standpoint of security, usability, capital efficiency of exits and more.
Today’s debaters are John Adler and Alex Gluchowski. John is the proposer of the original construction of the optimistic rollup and cofounded Celestia, and Alex is implementing a ZK rollup at Matter Labs. Our co-host James Prestwich is a security consultant and auditor for solidity contracts, among many other things.
If you’re into crypto and like to hear two sides of the story, be sure to also check out our previous episodes. We’ve featured some of the best known thinkers in the crypto space.
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Please note that nothing in our podcast should be construed as financial advice.
Source of select items discussed in the debate:

• Coindesk's layman guide for rollups: https://www.coindesk.com/ethereum-dapps-rollups-heres-why
• Alex Gluchowski on the difference between the two rollups: https://medium.com/matter-labs/optimistic-vs-zk-rollup-deep-dive-ea141e71e075
• John Adler explains optimistic rollup: https://medium.com/@adlerjohn/the-why-s-of-optimistic-rollup-7c6a22cbb61a
• Celestia: https://celestia.org/
• Fuel Labs: https://fuel.sh/
• Matter Labs: https://matter-labs.io/

Debater bios:
Alex Gluchowski is co-founder of Matter Labs, currently working on scaling Ethereum with zkSNARKs. He was previously CTO of PaulCamper, an online platform for sharing campervans and caravans in Europe.
John Adler is co-founder of Celestia and Fuel Labs. He is the original proposer of the optimistic rollup construction. He previously did layer-2 research at ConsenSys. Interestingly, he is a self-proclaimed blockchain skeptic.
James Prestwich founded cross-chain solution company Summa, subsequently acquired by the layer-1 blockchain firm Celo. He previously founded Storj, a decentralized cloud storage provider.