TL;DR:
- Aztec introduced its four-layer technology stack to offer programmable privacy on Ethereum as a decentralized layer 2 network.
- The Noir language, developed by Aztec, allows developers to write zero-knowledge programs without cryptographic expertise, with privacy enabled by default.
- The network currently has more than 3,500 active sequencers on its Alpha network, with sequencer and prover roles fully permissionless.
Aztec published a detailed technical description of its architecture, dubbed “The Aztec Stack,” explaining how its L2 network on Ethereum enables end-to-end programmable privacy for smart contract developers.
The Four Layers of Aztec
The system is organized into four layers. The first is Noir, a domain-specific programming language for zero-knowledge (zk) circuits with Rust-like syntax. Noir compiles code into zk circuits automatically through an intermediate representation called ACIR, compatible with multiple proving backends, including its own system Barretenberg. Privacy is the default behavior: all variables and functions remain private unless the developer explicitly indicates otherwise using the `pub` attribute.
Beyond Shielded Transactions
The second layer consists of smart contracts written with the Aztec.nr framework, which extends Noir to manage public and private state on-chain. A single contract can execute private functions on the user’s device and public functions on the network, combining them transparently. Account contracts implement account abstraction, enabling social account recovery, multifactor authentication, and granular access controls useful for regulatory compliance and tax reporting.
The third layer is the network itself. Private functions run in a private execution environment (PXE) on the user’s device, generating zk proofs that reveal no inputs, outputs, or identities. Public functions are processed by sequencers, who verify private proofs, execute public state, and publish state differences to Ethereum’s L1. Each epoch, defined as a sequence of 32 L2 blocks, receives a final proof generated by a decentralized prover network and published on-chain.
Noir Is Already Being Deployed
The fourth layer is Ethereum, which acts as the settlement layer: rollup proofs are anchored to L1, inheriting its economic security. The private state model uses UTXOs, while the public state replicates Ethereum’s account model.
Noir is already being used outside the Aztec ecosystem by projects building on Base, Scroll, and Starknet, evidencing its relevance as a standard language for zero-knowledge applications.
