Zero-Knowledge Rollups
Prerequisites
You should have a good understanding of all the foundational topics and a high-level understanding of Ethereum scaling. Implementing scaling solutions such as rollups is an advanced topic as the technology is less battle-tested and continues to be researched and developed.
Looking for a more beginner-friendly resource? See our introduction to layer 2.
Zero-knowledge rollups
Zero-knowledge rollups (ZK-rollups) bundle (or "roll-up") hundreds of transfers off-chain and generate a cryptographic proof. These proofs can come in the form of SNARKs (succinct non-interactive argument of knowledge) or STARKs (scalable transparent argument of knowledge). SNARKs and STARKs are known as validity proofs and get posted to layer 1.
The ZK-rollup smart contract maintains the state of all transfers on layer 2, and this state can only be updated with a validity proof. This means that ZK-rollups only need the validity proof instead of all transaction data. With a ZK-rollup, validating a block is quicker and cheaper because less data is included.
With a ZK-rollup, there are no delays when moving funds from layer 2 to layer 1 because a validity proof accepted by the ZK-rollup contract has already verified the funds.
Being on layer 2, ZK-rollups can be optimised to reduce transaction size further. For instance, an account is represented by an index rather than an address, which reduces a transaction from 32 bytes to just 4 bytes. Transactions are also written to Ethereum as calldata, reducing gas.
Pros and cons
| Pros | Cons |
|---|---|
| Faster finality time since the state is instantly verified once the proofs are sent to the main chain. | Some don't have EVM support. |
| Not vulnerable to the economic attacks that Optimistic rollups can be vulnerable to. | Validity proofs are intense to compute – not worth it for applications with little on-chain activity. |
| Secure and decentralized, since the data that is needed to recover the state is stored on the layer 1 chain. | An operator can influence transaction ordering. |
A visual explanation of ZK-rollups
Watch Finematics explain ZK-rollups:
Use ZK-rollups
Multiple implementations of ZK-rollups exist that you can integrate into your dapps:
ZK-rollups reading
