Aztec¶

Aztec is a privacy-first Layer 2 scaling solution (ZK-Rollup) on Ethereum. It aims to bring programmable privacy to the Ethereum ecosystem, allowing developers to build fully decentralized applications while protecting user data confidentiality by default. The Aztec network employs a unique UTXO model combined with zero-knowledge proof technology to enable encrypted transactions and private smart contract execution.

Problems It Solves¶

On public blockchains (such as Ethereum), all transaction data, account balances, and smart contract logic are completely public and transparent. While this transparency brings trust, it also introduces serious privacy issues:

Financial Privacy Leakage: Users' salaries, trading habits, and total assets are visible to everyone and easily tracked by on-chain analysis tools.
Trade Secret Risk: Enterprises cannot process supply chain finance, payroll, or sensitive commercial contracts on public chains because competitors can spy on their business activities.
MEV (Maximal Extractable Value): Because transaction content is public, miners or validators can front-run or sandwich user transactions, causing user losses.

Aztec is dedicated to solving these problems by providing a "default privacy" execution environment while maintaining Ethereum's security and composability.

Implementation Mechanism and Principles¶

Aztec's core technical architecture revolves around private state management and recursive zero-knowledge proofs.

Hybrid State Model (UTXO + Account)¶

To achieve privacy, Aztec adopts a UTXO (Unspent Transaction Output) model similar to Bitcoin for handling encrypted assets. This structure is naturally suited for privacy protection because each Note is independent and not directly linked to an account balance. At the same time, to support complex smart contract logic, Aztec combines Ethereum's account model, allowing public state and private state to coexist. * Private State: Stored as encrypted UTXOs in a Merkle Tree; only users with the decryption key can view and spend them. * Public State: Similar to Ethereum's public storage, visible to everyone.

Noir Programming Language¶

Aztec developed Noir, a Domain-Specific Language (DSL) designed specifically for zero-knowledge proofs. Developers use Noir to write Private Smart Contracts. The compiler converts high-level code into zero-knowledge circuits, enabling ordinary developers without deep cryptography backgrounds to build privacy applications.

Kernel Circuits and Rollup¶

Aztec uses "Kernel Circuits" to verify the correctness of individual transactions (including proofs of private function execution). 1. Client-Side Proving: The user's browser or local device generates the transaction's privacy proof (proving the right to spend funds without revealing the specific amount or recipient). 2. Recursive Aggregation: Aztec nodes (Sequencers) recursively aggregate multiple transaction proofs into a single large proof (Rollup Proof). 3. Ethereum Verification: The final aggregated proof is submitted to a smart contract on the Ethereum mainnet for verification, ensuring the correctness of Layer 2 state transitions.

Key Features¶

Programmable Privacy: Unlike Zcash, which only supports transfer privacy, Aztec supports general-purpose privacy smart contracts, enabling the construction of private DeFi, private DAOs, and encrypted games.
Dual State Trees: Simultaneously maintains private and public state trees, allowing applications to flexibly choose which data is public and which is confidential.
Decentralized Sequencers: Aztec plans to implement a decentralized sequencer network to avoid single points of failure and censorship risks.
Ethereum Security: As a Layer 2, Aztec's security is ultimately anchored on the Ethereum mainnet.