ZK-Proof Primer for Users

What you'll learn

• What Is a Zero-Knowledge Proof, In Plain Language?
• The Three Properties: Completeness, Soundness, Zero-Knowledge
• ZK Rollups: zkSync, StarkNet, Linea, Scroll
• ZK-EVM Type 1-4: Vitalik's Framework
• zk-SNARKs vs zk-STARKs and Trusted Setup
• Where Users Encounter ZK in Everyday Crypto
• The Future: ZK Verification, Identity, AI
• For Deeper Reading

Key terms

Zero-Knowledge Proof

A cryptographic procedure where a prover convinces a verifier that a statement is true without revealing the underlying information. Three properties: completeness, soundness, zero-knowledge.

Completeness, Soundness, Zero-Knowledge

The three properties defining a valid ZK proof. Completeness: honest provers always succeed. Soundness: cheating provers fail with overwhelming probability. Zero-knowledge: verifiers learn nothing beyond the truth.

zk-SNARK

Succinct Non-Interactive Argument of Knowledge. Small proofs (~few hundred bytes), fast verification (~milliseconds). Often requires trusted setup; not post-quantum secure. Constructions: Groth16, Plonk, Halo 2, Plonky2.

zk-STARK

Scalable Transparent Argument of Knowledge. Larger proofs (tens of KB) but no trusted setup and post-quantum secure. Used by StarkNet via Cairo. Original construction by Eli Ben-Sasson et al. 2018.

Trusted Setup

A one-time cryptographic ceremony to generate parameters for some SNARK constructions. Powers of Tau is the canonical multi-party version. Halo 2 (Zcash 2022) eliminated trusted setup for SNARKs.

ZK-EVM Type 1

Fully Ethereum-equivalent zkEVM — proves the exact EVM with no modifications. Maximum compatibility, highest proving cost. Taiko is closest to Type 1 in 2026; Linea has roadmapped it.

ZK-EVM Type 2

EVM-equivalent zkEVM with internal modifications for proving efficiency. Every existing contract works without changes. Scroll is the canonical Type 2; Linea launched as Type 2.

ZK-EVM Type 3

Almost-EVM-equivalent zkEVM with targeted compromises on hard-to-prove opcodes. Most contracts work; some need adjustments. Polygon zkEVM was Type 3.

ZK-EVM Type 4

High-level-language equivalent zkEVM — Solidity is compiled to ZK-friendly representation, not running EVM bytecode. zkSync Era and StarkNet (via Cairo) exemplify this.

Cairo

StarkWare's programming language for STARK-friendly computation. StarkNet uses Cairo natively. Solidity-to-Cairo transpilation via warp tooling enables EVM-style code on StarkNet.

Halo 2 (Zcash 2022)

SNARK construction that eliminates trusted setup by using a different polynomial commitment scheme. Adopted by Zcash and Aztec. Major advance in SNARK efficiency without setup ceremony.

ZK Hardware Acceleration

ASIC ZK provers (Cysic, Ingonyama, Ulvetanna) achieve 10x-100x speedup over CPU/GPU. Rapidly maturing in 2024-2026. Lowers proof costs and improves rollup finality.