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All of it begins with Ethereum. The L1 is simply too sluggish. Each node must redundantly re-execute transactions in a block to make sure validity, which limits scalability.
By 2020, the Ethereum group coalesced round rollups as the scaling resolution. Vitalik’s 2021 landmark weblog put up on rollups explains how optimistic and zk rollups can scale Ethereum.
Zk rollups are technologically superior for scaling however the tech was nonetheless too costly to make use of and much behind (extra later).
So optimistic rollups broke into the market first. Optimistic rollups assume all transactions are legitimate till somebody challenges it with a fraud proof inside a seven-day problem interval.
Optimistic rollups labored, however they got here with hidden prices. The problem interval meant longer transaction finality earlier than customers may withdraw funds. Locked liquidity meant capital efficiencies and a usually poorer UX, particularly with chain interoperability.
In the meantime, zk was catching up. At ETHCC 2022, Polygon, zkSync and Scroll all introduced zkEVMs, which allow Solidity devs to jot down code and show the execution of the EVM — successfully permitting Ethereum to leverage zero data expertise.
By 2023, zk rollups began to realize actual traction.
Why precisely are zk proofs higher than optimistic fraud proofs? Specifically as a result of zk proofs are a lot smaller (~1-10 KB) in comparison with uncooked transaction knowledge (megabytes in dimension).
Through the use of zk cryptography to show Ethereum transactions, these extremely compressed proofs meant decrease knowledge availability prices and higher scalability.
How zero data works in a nutshell
Although zk was taking off, proof technology was nonetheless costly. Primarily based on zkstats.io, the typical value to generate a zk proof in December 2023 was $80.21.
Quick ahead to 2025. Proof prices have dropped to $1.3 per proof, a couple of 98.4% enchancment.
What modified?
At this time, every of the core items of the zk rollup stack have been damaged up.
Firstly, zkVMs are right here. These specialised digital machines pace up the zk improvement expertise and make validity proof technology extra environment friendly. Earlier than zkVMs, builders wanted to jot down complicated, mathematical “circuits” to show EVM execution.
ZkVMs like SP1, RISC Zero, Nexus and OpenVM at the moment successfully democratize zk improvement for all builders (C++, Rust) with out zk cryptographic experience. Prior to now, zkEVMs solely enabled Solidity improvement on zk rollups. Consider zkVMs as a extra normal idea than zkEVMs.
Second, the prices to generate proofs are happening due to market competitors. At this time, there are a lot of aggressive marketplaces operated by Risc Zero, Cysic, Lagrange and Succinct. Some are nonetheless in testnet, some are operational.
Zk L2s are additionally turning to proof aggregation strategies to amortize verification prices. The best way this roughly works is by batching many proofs inside of 1, which makes the ultimate proof sooner to confirm.
These marketplaces are additionally permissionless, that means anybody with a GPU rig can enroll, put up a bond and generate zk proofs. Beforehand, zk rollups used “centralized provers,” that means they rented GPU/FPGA {hardware} from Google or Amazon.
Higher proof programs are additionally always launching. These proof programs (examples: Groth16, Halo2-KZG, STARK, Plonk, Expander) algorithmically outline the foundations as to how zk proofs are constructed and verified. They’re getting higher, which implies zk proofs are getting smaller and sooner to confirm. This in flip means elevated zkVM efficiency positive factors.
