Polygon Zero

Polygon Zero (formerly known as Mir) is a zero-knowledge (ZK) scaling protocol designed to massively increase the throughput and reduce the cost of transactions on the Ethereum network. It leverages zkSNARKs (Zero-Knowledge Succinct Non-Interactive Arguments of Knowledge), a cryptographic method that allows one party to prove to another that a statement is true without revealing any information beyond the validity of the statement itself. This enables the protocol to batch thousands of transactions off-chain, generate a single cryptographic proof, and post only that proof to Ethereum's Layer 1 for verification, ensuring Ethereum-level security with minimal on-chain data.

The protocol's core innovation is its Plonky2 proof system, a recursive zkSNARK that is exceptionally fast and efficient. Plonky2 is notable for being Ethereum Virtual Machine (EVM) compatible and written in Rust, allowing for rapid proof generation times—often in mere seconds—on consumer-grade hardware. This recursive proving capability allows Polygon Zero to create proofs of proofs, enabling the network to scale horizontally by combining multiple block proofs into a single, final proof, which dramatically improves scalability and reduces the computational load on the base chain.

As a key component of the Polygon 2.0 vision, Polygon Zero is architected to function as part of a unified, interoperable network of ZK-powered Layer 2 chains. Its design prioritizes developer accessibility by supporting the EVM, allowing existing Ethereum smart contracts and developer tooling to be ported with minimal changes. The protocol's ultimate goal is to serve as a foundational ZK coordination layer, enabling seamless cross-chain communication and liquidity flow across the entire Polygon ecosystem and beyond, forming what the team describes as the 'Value Layer' of the internet.

Polygon Zero works by using a zk-SNARK (Zero-Knowledge Succinct Non-Interactive Argument of Knowledge) validity rollup. This architecture bundles, or 'rolls up,' thousands of transactions off-chain into a single cryptographic proof. This succinct proof is then posted to the Ethereum mainnet for final settlement. The core innovation is the Plonky2 proving system, which enables extremely fast proof generation and verification, making the network both highly scalable and secure by inheriting Ethereum's consensus.

The process begins with a sequencer node collecting user transactions and executing them within its own virtual environment. It then generates a cryptographic commitment to the new state, known as a state root. Concurrently, a prover generates a zk-SNARK proof that attests to the correctness of all transactions in the batch and the resulting state transition. This proof is compact, often just a few hundred bytes, regardless of the batch size, which is what enables massive scalability.

Finally, the sequencer submits the new state root and the validity proof to a smart contract on Ethereum, called the verifier contract. This contract efficiently verifies the proof. Once confirmed, the new state root is accepted as canonical. This means users' funds are ultimately secured by Ethereum, while enjoying transaction costs that are a fraction of mainnet fees and near-instant finality after the proof is verified. The system's design ensures trustless operation, as the cryptographic proof guarantees correctness without requiring validators to re-execute transactions.

Plonky2 is a zero-knowledge succinct non-interactive argument of knowledge (zk-SNARK) that combines the best features of previous systems. Its primary innovation is being recursive and PLONK-based, while also utilizing FRI (Fast Reed-Solomon Interactive Oracle Proofs) for its polynomial commitments. This unique hybrid architecture allows it to generate proofs with remarkable speed and to verify them with minimal computational resources, a critical requirement for scaling blockchain networks.

A key breakthrough of Plonky2 is its use of a Goldilocks field (specifically, the field with modulus 2^64 - 2^32 + 1). Performing cryptographic operations in this 64-bit field, which is natively efficient on standard CPUs, is a major factor behind its performance gains. Furthermore, its recursive capability means Plonky2 can prove the correctness of another Plonky2 proof, enabling the aggregation of many proofs into a single one. This is essential for creating validium or zkEVM rollups that can batch thousands of transactions.

The system was engineered with Ethereum compatibility as a core goal. Plonky2 proofs are small enough to be posted as calldata on-chain, and their verification is cheap enough to be performed within Ethereum's gas constraints. This makes it a foundational technology for Layer 2 scaling solutions, where the security of Ethereum is leveraged while moving computation and state updates off-chain, only submitting a tiny proof to finalize transactions.

Developed by the team at Polygon Zero (formerly Mir Protocol), Plonky2 builds upon earlier work like PLONK and FRI but optimizes them for practical, high-throughput use cases. It serves as the proving engine for Polygon zkEVM, demonstrating its ability to handle the complex, stateful logic of the Ethereum Virtual Machine. Its open-source nature has also made it a popular choice for other ZK-rollup projects seeking high performance.

In summary, Plonky2 represents a significant leap in ZK-proof technology by delivering an optimal balance of proving time, proof size, and verification speed. Its design directly addresses the trilemma of being fast to prove, cheap to verify, and highly secure, positioning it as a cornerstone for the next generation of scalable, privacy-preserving blockchain applications.

The Polygon Zero project, originally known as Mir, was acquired by Polygon Labs in 2021 to become the cornerstone of its zkEVM (zero-knowledge Ethereum Virtual Machine) strategy. Its core innovation is Plonky2, a groundbreaking zero-knowledge proof (ZKP) system. Unlike earlier ZK schemes that required complex, trusted setups or were inefficient for general-purpose computation, Plonky2 combines the best of existing protocols—specifically the polynomial commitments from PLONK and the fast recursive proofs from FRI (Fast Reed-Solomon IOPP)—to create a proof system that is exceptionally fast and natively recursive.

Native recursion is Plonky2's superpower. It allows the system to efficiently verify proofs within proofs, enabling the aggregation of many transactions into a single, compact proof. This capability is critical for creating scalable zk-rollups, as it drastically reduces the computational load and data required for the final verification on the Ethereum mainnet. The speed of Plonky2, capable of generating proofs in under a second on a consumer laptop, addressed a major bottleneck in earlier ZK-rollup designs, making practical, high-throughput Layer 2 solutions feasible.

The development of Polygon Zero and Plonky2 provided the essential cryptographic engine for Polygon zkEVM, a Type 2 zkEVM that is fully equivalent to Ethereum. This means developers can deploy existing Ethereum smart contracts without modification, preserving the security and developer experience of Ethereum while benefiting from ZK-proof-verified scaling. The project's evolution reflects a broader industry shift from optimistic to zero-knowledge scaling solutions, prioritizing mathematical security guarantees over economic challenge periods.