Aztec v5 provides private smart contracts on Ethereum at the alpha launch

Aztec’s implementation layer shifts private computations to the device of the user, unlike Ethereum’s base-layer, which requires every validator to process and store transaction inputs and outputs to achieve consensus. In order to reduce the visible data of transactions, Aztec generates local cryptographic proofs before sending them on-chain for verification.

The client-side execution of private transactions is now different

A client-side execution engine with zero knowledge is integrated into Noir, Aztec’s domain-specific language for creating private smart contracts. Rather than executing private transactions on every node of the network like Ethereum Virtual Machine does, the system executes computations privately before generating recursive Succinct Non-Interactive arguments of Knowledge (SNARKs).

These proofs enable the network to validate that state changes have been made without disclosing plaintext inputs or transaction values. Aztec Labs claims that the model reduces unnecessary data sharing while maintaining mathematical assurances of transactions being executed correctly.

This architecture introduces an hybrid state-model to help overcome the engineering challenge that blockchains with privacy in mind face. Purely private environments are often unable to cope with multiple users updating the same state of the world at once, resulting in state contention.

Aztec has separated private state management from public to address this limitation. Public data and assets are maintained in key-value tree-like trees. Private assets, however, are kept on UTXO note trees. In the execution phase, private functions are able to generate public function calls which will then be handled later in the transaction cycle.

This model is designed to allow applications which require confidential computations while interacting with Ethereum’s public ecosystem.

Decentralized Finance and Enterprise Applications Targeted by Privacy Model

In addition to transactional privacy, this layer could also reduce some long-standing blockchain issues.

Aztec Labs says that before state committment, the transaction details will remain secret, which makes it much harder for observers outside to order pending transactions, or to exploit transaction data using Maximal Extractable Value.

This architecture provides the building blocks to build applications like confidential order matching systems, private liquidity provisioning and selective compliance system that only discloses required data through key viewing instead of disclosing complete records.

Aztec is known for its focus on programable privacy, rather than just anonymous token transfer.

Zac Williamson, co-founder of Aztec Labs and CEO Zac spoke to Crypto.news April 2025. He said that blockchain privacy goes beyond hiding wallet addresses. 

He described the privacy of users, confidentiality of transaction data and execution by private smart contracts as three important pillars for on-chain practical privacy. “the holy grail of blockchain privacy.” 

Williamson said that the privacy segment should not be considered a distinct industry. “all crypto will be private” As programmable privacy is incorporated into mainstream blockchain applications.

Williamson, in discussing compliance with privacy-preserving systems, said that they should use selective disclosure rather than complete anonymity. Williamson cited ZKPassport, a system that allows users to tap on an NFC-enabled passport and generate zero knowledge proofs. “what information you want to disclose,” It could be based on nationality or age. 

He claimed that the technology was “permissionless, it’s privacy preserving, and it ensures strong compliance,” Addition of such systems “a lot more powerful” They are more effective than other privacy solutions, as they combine privacy and programmable compliance.

Aztec Labs will expand on this vision in May 2026. acquired ZKPassport The platform for passport validation will remain open source. Aztec was able to integrate the privacy-focused infrastructure into their ecosystem. It allows developers to use programmable identity with zero knowledge identity verification on Ethereum-compatible networks.

It was already tested in Aztec’s system to reduce Sybil attacks. Participants could prove that they are unique without divulging their identity. During the AZTEC token sale, it was used for screening sanctions while keeping participants’ information confidential.

Alpha releases following security issues involving Legacy Products

Aztec Labs is now able to implement the execution layer, shortly after addressing security issues with products already retired.

Aztec Labs announced earlier this month that they were investigating a possible exploit for a payments product deprecated in 2021, launched after approximately $2 million was transferred From an immutable, smart contract. The affected system was discontinued by the company in 2022. It operated without administrator key, which prevented the team from pausing the contract or upgrading it.

Another deprecated software, Aztec Connect lost around $2.1 million when attackers took advantage of an immutable RollupProcessorV3 agreement. Aztec Labs stated that the incidents had nothing to do with the Aztec active network.

Aztec Foundation stated also that neither exploit was connected to the current Ethereum network, nor the AZTEC ERC-20 token. The Foundation stressed that both contracts were part of the legacy infrastructure and had remained on Ethereum long after the products have been retired.