Aztec Network
20 Sep
## min read

Announcing the Aztec Sandbox: The Endgame for Smart Contract Privacy

Aztec Labs introduces Sandbox, a testnet for building private blockchain applications, marking a major step in blockchain privacy solutions.

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Written by
Jon Wu
Edited by

The most ambitious software release in Aztec Labs’ history

Today we’re proud to announce the Aztec Sandbox, a local developer testnet for building end-to-end applications on Aztec.

Aztec is designed to be the endgame for blockchain privacy–the most complete solution for privacy-first blockchain applications ever attempted.

The Aztec Sandbox is the first milestone toward that endgame, allowing developers to write applications that leverage a full suite of privacy primitives:

  • Private smart contract composability (including public-private composability)
  • Private L1-L2 function calls
  • Private state management
  • Hidden function execution

All enabled by an intuitive software development environment that abstracts the complicated mechanisms necessary to protect user privacy.

⬇️ Download the Aztec Sandbox at sandbox.aztec.network.

Background

Aztec Labs has been laying the foundation for a privacy-preserving Ethereum L2 for years.

Yet building the Sandbox has taken just 5 months–a testament to the quality of our team and the ever-improving modularity of Aztec’s technology.

The Sandbox is the first major step on a development roadmap that includes a multi-phase testnet for Aztec’s execution environment, fee model, sequencers, and provers–all culminating in a privacy preserving zkRollup that is fully decentralized at mainnet launch.

What comes in the box?

The Aztec Sandbox is a comprehensive software release providing developers with a fast, lightweight local Aztec node, with features similar to Ethereum’s Ganache or Anvil local node packages.

Alongside Aztec’s local node testing environment, the Sandbox includes powerful tools and frameworks that allow developers to write and test smart contracts:

  • Aztec Node: build and publish rollup blocks with Aztec’s node software
  • Aztec RPC Server: decrypt and store client-side private state, execute private functions and submit transactions to the Aztec Node
  • Aztec.nr: write smart contracts using a comprehensive framework that extends Noir–an open-source zero knowledge programming language–with private smart contract functionality
  • Aztec.js: make RPC calls to an Aztec Node via Aztec’s Typescript wrapper
  • Aztec CLI: interact directly with an Aztec Node using Aztec’s command-line tool
  • Noir VS Code Extension: write Noir conveniently. Syntax highlighting, debugging and [other features] that make writing smart contracts in Noir utterly painless
  • Code examples: get inspired by Aztec Labs-written example private smart contracts and example wallet implementations

Developers should be aware that they are early adopters. You may encounter bugs or hiccups.

No fret.

For support related to the Aztec Sandbox, join our Discourse forum, where you can get hands-on support from Aztec Labs’ developer relation teams and build alongside the Aztec developer community.

🗣 Join the conversation on Aztec Labs’ Discourse

Get Started in Minutes

The Aztec Sandbox provides a local development system for building and testing Aztec smart contracts in a fast, safe, and free environment.

The process of downloading the Sandbox, installing client libraries, and using it to deploy and use a fully private token contract on a local Aztec node takes less than 10 minutes.

First, navigate to sandbox.aztec.network

Or curl the site:

/bin/bash -c "$(curl -fsSL 'https://sandbox.aztec.network')"

A package will then download and execute, spinning up two Docker containers:

  • Anvil
  • Aztec Sandbox

The Sandbox will create servers on localhost ports 8545 (Anvil) and 8080 (Sandbox); ensure those ports are free to prevent any conflicts.

Within a few seconds the Sandbox should be up and running!

What can you do with it

The Sandbox is the starting point for Aztec smart contract and application developers. The Sandbox helps future-looking developers get a head-start interacting with ZK-native blockchain environments.

And as pioneers in smart contract privacy, developers will need to add a few useful heuristics to their public-blockchain mental models. Some new concepts include:

  • Private state management
  • Account abstraction models
  • Understanding patterns to keep private information private
  • Transaction paths which span both private and public function execution
  • Organizing contracts into privately executable logic and publicly executable logic

For more about UTXO abstraction and how Aztec makes it convenient to manage manipulating private state, read our blog post here. For more information relating to privacy preservation best practices, see here. And for more about transaction architecture, see here.

Using Aztec.js, developers can build full-fledged applications that let users:

  • write, deploy and test private smart contracts
  • create accounts (choosing one of various account abstraction schemes!)
  • manage their wallets
  • send transactions to the network and track their progress
  • query current chain state such as chain ID, block number, etc.

Learn more about how to write an Aztec smart contract along with ready-made examples and walkthrough guides here.

Use-cases we’re excited to see

Aztec’s smart contract examples include a broad swath of use cases

  • Public and private token contracts
  • Private DeFi
  • Oracle price feeds
  • Air-drop contracts
  • Two-party private escrow
  • Account contracts that can privately validate account credentials

We’re excited to see other application primitives including private identity, fully on-chain private games, and decentralized finance protocols offering privacy by default.

We can’t wait to see the explosion of higher-order privacy mechanisms that will be created by remixing and composing these basic primitives into complex smart contracts and full-fledged privacy-first applications.

What you can’t do (yet)

The Aztec Sandbox is our minimum viable local developer testnet. While developers can begin writing smart contracts, there is no shared in-production network.

While account creation, wallet management, smart contract creation, and transaction execution are all live, fee estimation, transaction sequencing, proving, and advanced key and address functionality will be released in future iterations of the Sandbox.

🎻 For a full current list of limitations see here.

You can learn how to write and test Aztec smart contracts. You just can’t deploy production applications–yet.

What is Noir’s relationship to all this?

Aztec Labs first developed Noir as a standalone, open-source, universal language for zero-knowledge programming. Noir is designed to be compatible across proving systems while also being verifiable to any chain, not just Aztec.

​​It’s no surprise then, that we’ve chosen Noir as a basis for writing smart contracts on Aztec. Using Noir, we’ve written a collection of functions, types, methods, state variables, annotations, etc. which together provide a rich, syntactically pleasing framework, to aid developers in writing intuitive and legible private smart contracts.

Imaginatively, we called this framework Aztec.nr.

Aztec applications written with the Aztec.nr framework have the advantage of features and tools developers might expect to be packaged with any smart contract framework:

  • Contracts (including callable contract functions and inter-contract function calls)
  • Persistent state variables
  • Contract address semantics
  • Access to msg.sender and other call context information
  • Access to transaction context information
  • Access to historic blockchain data
  • Events (logs) (both encrypted and unencrypted)
  • Cryptographic primitives
  • Cross-chain (L1 -> L2 and L2 -> L1) message passing

Noir is an open-source language with universal applicability to zero knowledge use-cases. In fact, our hope is Noir’s extensibility allows it to be used even in non-blockchain / web2 applications!

But with Aztec.nr, Noir now fits hand-in-glove with Aztec. Noir developers now have access to the best privacy infrastructure for their applications.

Noir developers: it’s time to come home.

🏃 Get started now at sandbox.aztec.network.

Front-run the future

Joining now as a Sandbox developer represents a significant opportunity to gain early access and bend the blockchain universe toward more privacy, not less.

At Aztec Labs we’ve worked tirelessly to make zero knowledge cryptography accessible to non-cryptographers. The Aztec Sandbox now delivers that promise in a developer-friendly package.

We’re excited by the opportunity represented by this release to begin democratizing access to fully decentralized privacy-enabled applications.

We hope you are too.

Get started

The fastest way to get going with the Aztec Sandbox is our starter page at sandbox.aztec.network, which allows you to download the Sandbox, deploy an example private token contract, and do basic interactions with the contract to transfer tokens between private addresses via the Aztec CLI.

Additional resources:

Read more
Aztec Network
Aztec Network
31 Mar
xx min read

Announcing the Alpha Network

Alpha is live: a fully feature-complete, privacy-first network. The infrastructure is in place, privacy is native to the protocol, and developers can now build truly private applications. 

Nine years ago, we set out to redesign blockchain for privacy. The goal: create a system institutions can adopt while giving users true control of their digital lives. Privacy band-aids are coming to Ethereum (someday), but it’s clear we need privacy now, and there’s an arms race underway to build it. Privacy is complex, it’s not a feature you can bolt-on as an afterthought. It demands a ground-up approach, deep tech stack integration, and complete decentralization.

In November 2025, the Aztec Ignition Chain went live as the first decentralized L2 on Ethereum, it’s the coordination layer that the execution layer sits on top of. The network is not operated by the Aztec Labs or the Aztec Foundation, it’s run by the community, making it the true backbone of Aztec. 

With the infrastructure in place and a unanimous community vote, the network enters Alpha. 

What is the Alpha Network?

Alpha is the first Layer 2 with a full execution environment for private smart contracts. All accounts, transactions, and the execution itself can be completely private. Developers can now choose what they want public and what they want to keep private while building with the three privacy pillars we have in place across data, identity, and compute.

These privacy pillars, which can be used individually or combined, break down into three core layers: 

  1. Data: The data you hold or send remains private, enabling use cases such as private transactions, RWAs, payments and stablecoins.
  2. Identity: Your identity remains private, enabling accounts that privately connect real world identities onchain, institutional compliance, or financial reporting where users selectively disclose information.
  3. Compute: The actions you take remain private, enabling applications in private finance, gaming, and beyond.

The Key Components  

Alpha is feature complete–meaning this is the only full-stack solution for adding privacy to your business or application. You build, and Aztec handles the cryptography under the hood. 

It’s Composable. Private-preserving contracts are not isolated; they can talk to each other and seamlessly blend both private and public state across contracts. Privacy can be preserved across contract calls for full callstack privacy. 

No backdoor access. Aztec is the only decentralized L2, and is launching as a fully decentralized rollup with a Layer 1 escape hatch.

It’s Compliant. Companies are missing out on the benefits of blockchains because transparent chains expose user data, while private networks protect it, but still offer fully customizable controls. Now they can build compliant apps that move value around the world instantly.

How Apps Work on Alpha 

  1. Write in Noir, a proprietary rust-like programming language for writing smart contracts. Build contracts with Aztec.nr and mark functions private or public.
  1. Prove on a device. Users execute private logic locally and a ZK proof is generated.
  1. Submit to Aztec. The proof goes to sequencers who validate without seeing the data. Any public aspects are then executed.
  1. Settle on Ethereum. Checkpoints batch proofs to L1 every ~12s. Ethereum verifies everything. 

Developers can explore our privacy primitives across data, identity, and compute and start building with them using the documentation here. Note that this is an early version of the network with known vulnerabilities, see this post for details. While this is the first iteration of the network, there will be several upgrades that secure and harden the network on our path to Beta. If you’d like to learn more about how you can integrate privacy into your project, reach out here

To hear directly from our Cofounders, join our live from Cannes Q&A on Tuesday, March 31st at 9:30 am ET. Follow us on X to get the latest updates from the Aztec Network.

Aztec Network
Aztec Network
27 Mar
xx min read

Critical Vulnerability in Alpha v4

On Wednesday 17 March 2026 our team discovered a new vulnerability in the Aztec Network. Following the analysis, the vulnerability has been confirmed as a critical vulnerability in accordance with our vulnerability matrix.

The vulnerability affects the proving system as a whole, and is not mitigated via public re-execution by the committee of validators. Exploitation can lead to severe disruption of the protocol and theft of user funds.

In accordance with our policy, fixes for the network will be packaged and distributed with the “v5” release of the network, currently planned for July 2026.

The actual bug and corresponding patch will not be publicly disclosed until “v5.”

Aztec applications and portals bridging assets from Layer 1s should warn users about the security guarantees of Alpha, in particular, reminding users not to put in funds they are not willing to lose. Portals or applications may add additional security measures or training wheels specific to their application or use case.

State of Alpha security

We will shortly establish a bug tracker to show the number and severity of bugs known to us in v4. The tracker will be updated as audits and security researchers discover issues. Each new alpha release will get its own tracker. This will allow developers and users to judge for themselves how they are willing to use the network, and we will use the tracker as a primary determinant for whether the network is ready for a "Beta" label.

Additional bug disclosure

We have identified a vulnerability in barretenberg allowing inclusion of incorrect proofs in the Aztec Network mempool, and ask all nodes to upgrade to versions v.4.1.2 or later.

We’d like to thank Consensys Diligence & TU Vienna for a recent discovery of a separate vulnerability in barretenberg categorized as medium for the network and critical for Noir:

We have published a fixed version of barretenberg.

We’d also like to thank Plainshift AI for discovery, reproduction, and reporting of one more vulnerability in the Aztec Network and their ongoing work to help secure the network.

Aztec Network
Aztec Network
18 Mar
xx min read

How Aztec Governance Works

Decentralization is not just a technical property of the Aztec Network, it is the governing principle. 

No single team, company, or individual controls how the network evolves. Upgrades are proposed in public, debated in the open, and approved by the people running the network. Decentralized sequencing, proving, and governance are hard-coded into the base protocol so that no central actor can unilaterally change the rules, censor transactions, or appropriate user value.

The governance framework that makes this possible has three moving parts: Aztec Improvement Proposal (AZIP), Aztec Upgrade Proposal (AZUP), and the onchain vote. Together, they form a pipeline that takes an idea to a live protocol change, with multiple independent checkpoints along the way.

The Virtual Town Square

Every upgrade starts with an AZIP. AZIPs are version-controlled design documents, publicly maintained on GitHub, modeled on the same EIP process that has governed Ethereum since its earliest days. Anyone is encouraged to suggest improvements to the Aztec Network protocol spec.

Before a formal proposal is opened, ideas live in GitHub Discussions, an open forum where the community can weigh in, challenge assumptions, and shape the direction of a proposal before it hardens into a spec. This is the virtual town square: the place where the network's future gets debated in public, not decided behind closed doors.

The AZIP framework is what decentralization looks like in practice. Multiple ideas can surface simultaneously, get stress-tested by the community, and the strongest ones naturally rise. Good arguments win, not titles or seniority. The process selects for quality discussion precisely because anyone can participate and everything is visible.

Once an AZIP is formalized as a pull request, it enters a structured lifecycle: Draft, Ready for Discussion, then Accepted or Rejected. Rejected AZIPs are not deleted — they remain permanently in the repository as a record of what was tried and why it was rejected. Nothing gets quietly buried.

Security Considerations are mandatory for all Core, Standard, and Economics AZIPs. Proposals without them cannot pass the Draft stage. Security is structural, not an afterthought.

From Proposal to Upgrade

Once Core Contributors, a merit-based and informal group of active protocol contributors, have reviewed an AZIP and approved it for inclusion, it gets bundled into an AZUP.

An AZUP takes everything an AZIP described and deploys it — a real smart contract, real onchain actions. Each AZUP includes a payload that encodes the exact onchain changes that will occur if the upgrade is approved. Anyone can inspect the payload on a block explorer and see precisely what will change before voting begins.

The payload then goes to sequencers for signaling. Sequencers are the backbone of the network. They propose blocks, attest to state, and serve as the first governance gate for any upgrade. A payload must accumulate enough signals from sequencers within a fixed round to advance. The people actually running the network have to express coordinated support before any change reaches a broader vote.

Once sequencers signal quorum, the proposal moves to tokenholders. Sequencers' staked voting power defaults to "yea" on proposals that came through the signaling path, meaning opposition must be active, not passive. Any sequencer or tokenholder who wants to vote against a proposal must explicitly re-delegate their stake before the voting snapshot is taken. The system rewards genuine engagement from all sides.

For a proposal to pass, it must meet quorum, a supermajority margin, and a minimum participation threshold, all three. If any condition is unmet, the proposal fails.

Built-In Delays, Built-In Safety

Even after a proposal passes, it does not execute immediately. A mandatory delay gives node operators time to deploy updated software, allows the community to perform final checks, and reduces the risk of sudden uncoordinated changes hitting the network. If the proposal is not executed within its grace period, it expires.

Failed AZUPs cannot be resubmitted. A new proposal must be created that directly addresses the feedback received. There is no way to simply retry and hope for a different result.

No Single Point of Control

The teams building the network have no special governance power. Sequencers, tokenholders, and Core Contributors are the governing actors, each playing a distinct and non-redundant role.

No single party can force or block an upgrade. Sequencers can withhold signals. Tokenholders can vote nay. Proposals not executed within the grace period expire on their own.

This is decentralization working as intended. The network upgrades not because a team decides it should, but because the people running it agree that it should.

If you want to help shape what Aztec becomes, the forum is open. The proposals are public. The town square is yours. 

Follow Aztec on X to stay up to date on the latest developments.

Aztec Network
Aztec Network
10 Mar
xx min read

Alpha Network Security: What to Expect

Aztec’s Approach to Security

Aztec is novel code — the bleeding edge of cryptography and blockchain technology. As the first decentralized L2 on Ethereum, Aztec is powered by a global network of sequencers and provers. Decentralization introduces some novel challenges in how security is addressed; there is no centralized sequencer to pause or a centralized entity who has power over the network. The rollout of the network reflects this, with distinct goals at each phase.

Ignition

Validate governance and decentralized block building work as intended on Ethereum Mainnet. 

Alpha

Enable transactions at 1TPS, ~6s block times and improve the security of the network via continual ongoing audits and bug bounty. New releases of the alpha network are expected regularly to address any security vulnerabilities. Please note, every alpha deployment is distinct and state is not migrated between Alpha releases. 

Beta

We will transition to Beta once the network scales to >10 TPS, with reduced block times while ensuring 99.9% uptime. Additionally, the transition requires no critical bugs disclosed via bug bounty in 3 months. State migrations across network releases can be considered.

TL;DR: The roadmap from Ignition to Alpha to Beta is designed to reflect the core team's growing confidence in the network's security.

This phased approach lets us balance ecosystem growth while building security confidence and steadily expanding the community of researchers and tools working to validate the network’s security, soundness and correctness.

Ultimately, time in production without an exploit is the most reliable indicator of how secure a codebase is.

At the start of Alpha, that confidence is still developing. The core team believes the network is secure enough to support early ecosystem use cases and handle small amounts of value. However this is experimental alpha software and users should not deposit more value than they are willing to lose. Apps may choose to limit deposit amounts to mitigate risk for users.

Audits are ongoing throughout Alpha, with the goal to achieve dual external audits across the entire codebase.

The table below shows current security and audit coverage at the time of writing.

The main bug bounty for the network is not yet live, other than for the non-cryptographic L1 smart contracts as audits are ongoing. We encourage security researchers to responsibly disclose findings in line with our security policy .

As the audits are still ongoing, we expect to discover vulnerabilities in various components. The fixes will be packaged and distributed with the “v5” release.

If we discover a Critical vulnerability in “v4” in accordance with the following severity matrix, which would require the change of verification keys to fix, we will first alert the portal operators to pause deposits and then post a message on the forum, stating that the rollup has a vulnerability.

Security of the Aztec Virtual Machine (AVM)

Aztec uses a hybrid execution model, handling private and public execution separately — and the security considerations differ between them.

As per the audit table above, it is clear that the Aztec Virtual Machine (AVM) has not yet completed its internal and external audits. This is intentional as all AVM execution is public, which allows it to benefit from a “Training Wheel” — the validator re-execution committee.

Every 72 seconds, a collection of newly proposed Aztec blocks are bundled into a "checkpoint" and submitted to L1. With each proposed checkpoint, a committee of 48 staking validators randomly selected from the entire set of validators (presently 3,959) re-execute all txs of all blocks in the checkpoint, and attest to the resulting state roots. 33 out of 48 attestations are required for the checkpoint proposal to be considered valid. The committee and the eventual zk proof must agree on the resultant state root for a checkpoint to be added to the proven chain. As a result, an attacker must control 33/48 of any given committee to exploit any bug in the AVM.

The only time the re-execution committee is not active is during the escape hatch, where the cost to propose a block is set at a level which attempts to quantify the security of the execution training wheel. For this version of the alpha network, this is set a 332M AZTEC, a figure intended to approximate the economic protection the committee normally provides, equivalent to roughly 19% of the un-staked circulating supply at the time of writing. Since the Aztec Foundation holds a significant portion of that supply, the effective threshold is considerably higher in practice.

Quantifying the cost of committee takeover attacks

A key design assumption is that just-in-time bribery of the sequencer committee is impractical and the only ****realistic attack vector is stake acquisition, not bribery.

Assuming a sequencer set size of 4,000 and a committee that rotates each epoch (~38.4mins) from the full sequencer set using a Fisher-Yates shuffle seeded by L1 RANDAO we can see the probability and amount of stake required in the table below.

To achieve a 99% probability of controlling at least one supermajority within 3 days, an attacker would need to control approximately 55.4% of the validator set - roughly 2,215 sequencers representing 443M AZTEC in stake. Assuming an exploit is successful their stake would likely de-value by 70-80%, resulting in an expected economic loss of approximately 332M AZTEC.

To achieve only a 0.5% probability of controlling at least one supermajority within 6 months, an attacker would need to control approximately 33.88% of the validator set.

What does this means for builders?

The practical effect of this training wheel is that the network can exist while there are known security issues with the AVM, as long as the value an attacker would gain from any potential exploit is less than the cost of acquiring 332M AZTEC.

The training wheel allows security researchers to spend more time on the private execution paths that don’t benefit from the training wheel and for the network to be deployed in an alpha version where security researchers can attempt to find additional AVM exploits.

In concrete terms, the training wheel means the Alpha network can reasonably secure value up to around 332M AZTEC (~$6.5M at the time of writing).

Ecosystem builders should keep the above limits in mind, particularly when designing portal contracts that bridge funds into the network.

Portals are the main way value will be bridged into the alpha network, and as a result are also the main target for any exploits. The design of portals can allow the network to secure far higher value. If a portal secures > 332M AZTEC and allows all of its funds to be taken in one withdrawal without any rate limits, delays or pause functionality then it is a target for an AVM exploit attack.

If a portal implements a maximum withdrawal per user, pause functionality or delays for larger withdrawals it becomes harder for an attacker to steal a large quantum of funds in one go.

Conclusion

The Aztec Alpha code is ready to go. The next step is for someone in the community to submit a governance proposal and for the network to vote on enabling transactions. This is decentralization working as intended.

Once live, Alpha will run at 1 TPS with roughly 6 second block times. Audits are still ongoing across several components, so keep deposits small and only put in what you're comfortable losing.

On the security side, a 48-validator re-execution committee provides the main protection during Alpha, requiring 33/48 consensus on every 72-second checkpoint. Successfully attacking the AVM would require controlling roughly 55% of the validator set at a cost of around 332M AZTEC, putting the practical security ceiling at approximately $6.5M.

Alpha is about growing the ecosystem, expanding the security of the network, and accumulating the one thing no audit can shortcut: time in production. This is the network maturing in exactly the way it was designed to as it progresses toward Beta.