Aztec v5 released in Alpha version, bringing private smart contracts to Ethereum

Aztec releases an Alpha version of the v5 execution layer, introducing a programmable privacy framework for Ethereum

Aztec has launched an Alpha version of its v5 execution layer, which introduces a programmable privacy framework that enables Ethereum applications to handle public and private states in the same Layer-2 environment.

Overview

Aztec has released an Alpha version of the v5 execution layer, bringing programmable privacy to Ethereum through zero-knowledge-driven smart contracts. The new architecture migrates private computing processes to user devices while verifying transactions on the chain without exposing sensitive data. Aztec said the executive layer supports confidential decentralized applications and is designed to reduce the risk of rushing and MEV.

Aztec Labs announced the Alpha version of the v5 execution layer and described it as an important step towards implementing privacy-native smart contracts on Ethereum. The new architecture allows developers to build decentralized applications that combine confidential user data with public blockchain status, while relying on zero-knowledge proof to verify transactions without exposing sensitive information.

Unlike the Ethereum base layer, where each verifier needs to process and store transaction input, output and execution data to reach consensus, Aztec's execution layer moves private computing to user devices. The system does not disclose transaction details on the network, but instead generates encryption certificates locally and then submits them to on-chain verification, thereby reducing the amount of visible transaction data while retaining Ethereum's security.

Client execution changes how private transactions are processed

The core of this release is the client-side zero-knowledge execution engine integrated into Noir. Noir is a domain-specific programming language developed by Aztec for private smart contracts. Unlike the Ethereum virtual machine, which performs confidential transactions on all network nodes, the architecture performs private calculations on user hardware and then generates a recursive concise non-interactive demonstration of knowledge (SNARK). These certificates allow the network to verify the validity of state changes without exposing clear text input, transaction values, or account identities. According to Aztec Labs, the model reduces unnecessary data disclosures with mathematical guarantees that transactions are executed correctly.

The architecture also introduces a mixed-state model designed to solve one of the biggest engineering challenges facing privacy blockchains. Purely private execution environments often experience state contention when multiple users simultaneously attempt to update the same public state, limiting interaction with shared decentralized financial infrastructure. To address this limitation, Aztec separates private state management from public state management. Private assets are stored in a note tree similar to UTXO, while public data is maintained through key-value trees. During execution, private functions can generate delayed public function calls that will be processed later in the same transaction life cycle, allowing confidential operations to work in conjunction with public operations without sacrificing deterministic execution or raising race conditions. The execution model is designed to support applications that require confidential computing while simultaneously interacting with the Ethereum public ecosystem, including shared liquidity pools and other decentralized financial protocols.

The privacy model targets decentralized financial and enterprise applications

In addition to transaction privacy, this execution layer also introduces multiple functions that are expected to reduce several long-term problems in blockchain execution. According to Aztec Labs, transaction details remain hidden until status is submitted, making it extremely difficult for external observers to reorder outstanding transactions or leverage visible transaction data through a maximum extractable value strategy. The architecture also provides building blocks for applications such as confidential order matching, private liquidity provisioning, and selective compliance systems. These systems disclose only necessary information by viewing keys, rather than exposing complete user records.

These capabilities are built on Aztec's long-standing focus on programmable privacy, rather than simply anonymous token transfers. Zac Williamson, co-founder and CEO of Aztec Labs, has said that blockchain privacy should go beyond hiding wallet addresses. He described user privacy, confidential transaction data, and private smart contract execution as the three pillars needed for privacy on the utility chain, calling it the "Holy Grail of blockchain privacy." Williamson also believes that privacy should not be seen as a separate segment of the industry and that as programmable privacy becomes part of mainstream blockchain applications,"all encryption will be privatized." When discussing compliance, Williamson said the privacy protection system should rely on selective disclosure rather than full anonymity. He cited ZKPassport as an example, pointing out that users can generate zero-knowledge certificates through NFC passports and choose "what information to disclose," whether it is nationality, age or other identity attributes. He called the technology "permission-free, privacy-friendly, and ensures strong compliance," adding that such systems are "much more powerful" than existing privacy solutions because they combine privacy with programmable compliance.

This vision was further expanded in May 2026, when Aztec Labs acquired ZKPassport and committed to keeping the passport verification platform open source. The acquisition integrates this privacy-centric identity infrastructure directly into the Aztec ecosystem, allowing developers to combine programmable privacy with zero-knowledge authentication in an Ethereum-compatible network. The technology, which has been tested on the Aztec network, helps reduce witch attacks and allows participants to prove that they are unique individuals without revealing their identities. During AZTEC token sales, the technology was also used to conduct sanctions screening while maintaining the privacy of participant information.

Security incident involving legacy products occurred before the release of Alpha version

The release of the executive layer came shortly after Aztec Labs addressed security issues involving retired products. Earlier this month, Aztec Labs disclosed that it was investigating a potential exploit involving a deprecated payment product released in 2021, when approximately $2 million was transferred from immutable smart contracts. The company said the affected systems were decommissioned in 2022 and had no administrator keys, making it impossible for the team to suspend or upgrade the contract. In addition, another deprecated product, Aztec Connect, lost approximately $2.1 million after attackers took advantage of the old immutable RollupProcessor V3 contract. Aztec Labs stated that these incidents were not related to the current active Aztec network. The Aztec Foundation also emphasized that the two exploits were not related to the current network or the AZTEC ERC-20 token, pointing out that the affected contracts were legacy infrastructure and that these products remained on Ethereum after retirement.