| Authors | Matter Labs (Alex Gluchowski, Alexandr Vlasov, et al.) |
|---|---|
| Year | 2020 |
| Project | zkSync |
| License | MIT / Apache 2.0 |
| Official Source | https://github.com/matter-labs/zksync |
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zkSync is a ZK-Rollup for Ethereum developed by Matter Labs, founded by Alex Gluchowski. The original zkSync 1.0 (later renamed zkSync Lite) launched in June 2020 as a payment and token transfer rollup. The upgraded zkSync Era launched March 2023 as a full zkEVM — a ZK-Rollup capable of executing arbitrary Ethereum smart contracts. The technical foundation rests on the PLONK proving system and Matter Labs’ custom zkEVM circuit design.
The principal technical specification is the zkSync Era specification and the ZK-EVM boojum proving system documentation.
> Source: The original Hermez zkSync paper is at Matter Labs’ GitHub. Current zkSync Era documentation is at docs.zksync.io. The Boojum prover is at github.com/matter-labs/era-boojum.
Publication and Context
The zero-knowledge rollup category began not with a single paper but with practical engineering work. Buterin described ZK-Rollups theoretically; Matter Labs built the first production ZK-Rollup for Ethereum in 2020. At the time, ZK-SNARKs could prove simple arithmetic efficiently but full EVM execution was considered too complex to prove.
The race to build a zkEVM — a ZK-Rollup that proves full EVM execution — defined the 2021–2024 ZK landscape. Matter Labs, Polygon Hermez, Scroll, and Taiko all built different approaches.
Matter Labs differentiated itself with:
- Custom LLVM-based zkEVM compiler for Solidity and Yul
- Novel Boojum proof system (a PLONK variant)
- Aggressive ZK circuit compression for EVM opcode proving
- Focus on developer experience and EVM compatibility
zkSync Lite (Original Design)
zkSync Lite handles ETH and ERC-20 token transfers with:
- Batch processing: Hundreds of transactions batched into one proof
- Merkle state tree: Account balances stored off-chain; Merkle root committed on-chain
- PLONK proofs: Each batch’s validity proved via PLONK (with a universal trusted setup)
- On-chain data availability: Compressed state diffs posted to Ethereum
The key property: transfers are final with Ethereum security guarantees once the ZK proof is verified on-chain. No fraud proof window; instant finality.
zkSync Era: zkEVM Architecture
zkSync Era proves full EVM execution (with some differences from the EVM specification). The stack:
Compiler pipeline:
- Solidity/Vyper source code → zkSync LLVM IR via custom compiler (
zksolc,zkvyper) - LLVM IR → zkEVM bytecode (a custom RISC-like instruction set optimized for ZK proving)
- zkEVM bytecode executes in the zkEVM circuit
Why a custom IR? The EVM’s 256-bit word size and specific opcodes are expensive to prove in ZK circuits. zkSync Era’s compiler translates EVM semantics to a representation that minimizes circuit size.
Boojum Prover:
The Boojum proving system (Matter Labs, 2023) is a highly optimized PLONK-based prover with:
- GPU acceleration for proof generation
- Recursive proof aggregation
- SNARK-compressed proofs posted to Ethereum
Transaction lifecycle:
| Phase | Description |
|---|---|
| Sequencer receives tx | Processes EVM-compatible transactions |
| Backend execution | zkEVM executes the transaction trace |
| Proof generation | Boojum generates SNARK proof |
| L1 submission | Proof + compressed state diff posted to Ethereum |
| Verification | Solidity verifier checks proof on-chain → finalized |
EVM Compatibility Nuances
zkSync Era is EVM-compatible but not EVM-equivalent. Differences include:
- Precompiles: Some Ethereum precompiles are emulated in software (may have higher gas costs)
- Storage model: Different gas schedule for storage operations
- Nonce handling: Contract nonces behave differently at deploy
- SELFDESTRUCT: Removed for ZK efficiency reasons
In practice, the vast majority of Solidity contracts deploy without modification. The differences affect edge cases.
The ZKsync Ecosystem
Matter Labs launched ZK Stack in 2023 — an open-source framework for building “Hyperchains” (ZK-powered VM chains) that share bridging infrastructure with zkSync Era. This mirrors the OP Stack approach but for ZK proofs. Early Hyperchains include Cronos zkEVM, Abstract, and Lens Protocol’s chain.
Reality Check
zkSync Era launched without an airdrop announcement, accumulated $700M+ TVL quickly, then airdropped the ZK token in June 2024 — but the airdrop allocation was widely criticized as too small per user and weighted toward bots. The tokenomics gave a large portion to investors and insiders. Security: zkSync had one significant incident in 2024 where a $5M token bug was discovered in an airdrop contract (recovered by a whitehat). No user funds were lost. Proving costs remain high; zkSync depends on hardware improvements and proof aggregation to reach full cost parity with optimistic rollups.
Related Terms
Research
- Gluchowski, A. (2020). zkSync: Scaling and Privacy Engine for Ethereum. matter-labs.io.
— Original zkSync Lite technical overview; describes the PLONK-based batching scheme.
- Gabizon, A., Williamson, Z.J., & Ciobotaru, O. (2019). PLONK: Permutations over Lagrange-bases for Oecumenical Noninteractive arguments of Knowledge. IACR ePrint 2019/953.
— The PLONK proving system; the cryptographic foundation of zkSync’s proofs.
- Buterin, V. (2021). The Different Types of ZK-EVMs. vitalik.eth.limo.
— Taxonomy post placing zkSync Era as a “Type 4 ZK-EVM” (custom VM / best compatibility trade-off).