Aztec Network
25 Mar
## min read

Privacy for Pennies: Scaling Aztec’s zkRollup

Learn how how Aztec's ZkRollup achieves scalable blockchain privacy at a minimal cost, enhancing both efficiency and security.

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Written by
Jon Wu
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The economics of our privacy-first Ethereum rollup.

Our goal at Aztec is to make privacy a no-brainer. That’s why our rollup is designed to give you fully private Ethereum transactions at dramatically lower cost than mainnet.

We consider privacy a critical missing component of Ethereum’s scalability roadmap, given that its user functionality is non-economic in nature.

But privacy must also be affordable, and in order to understand how we’ll get to privacy for cheap, we need to do a deeper study of rollup economics.

Background on Ethereum scaling

You might already be familiar with the difference between the two consensus Ethereum scaling solutions: Optimistic Rollups (ORUs) and zkRollups (ZKRs). I’ll let Vitalik explain here.

But in case you want my take, here’s the basic trade-off between Optimistic Rollups and zkRollups:

Optimistic

Optimistic rollup block producers post an Ethereum transaction containing a state root. The ecosystem “optimistically” takes the state of the system to be valid.

During a 7 day challenge period, anyone can prove the invalidity of the state transition by downloading the block of transactions and comparing the previous Merkle root state to the new Merkle root state.

If there is an invalid state transition, they can submit a fraud proof, causing the block producer to be slashed and the blockchain state to be rolled back to its original state.

Note that the cost of executing transactions with an optimistic rollup is very close to free, since it’s essentially the cost of computation as done by a single sequencer (just like, a computer somewhere). However, there is still a variable cost of posting data to Ethereum.

Zero-knowledge

In a zero-knowledge rollup, the rollup incurs a significant fixed cost. Rather than passively awaiting fraud proofs, ZKRs proactively post a succinct zero knowledge proof to Ethereum Layer 1 validating a set of off-chain computations (a “validity proof”).

While the security of off-chain transactions in a zkRollup is unimpeachable due to the deterministic nature of zero knowledge proofs, there must be sufficiently high transaction throughput to amortize the cost of posting the proof to Ethereum.

Tl;dr:

  • Optimistic: no fixed costs, finality delayed by 7 day challenge & withdrawal period; in case of fraud, blockchain state gets rolled back
  • zk: high fixed costs, finality limited by speed of rollup, no challenge or withdrawal period, no possible fraud (caveat: as long as the cryptography works as intended)

Simple rollup math

Aztec, of course is a zero-knowledge rollup. (In fact, it’s a recursive zk-rollup–a zk-zk-rollup, but we’ll get to that).

That means it does incur the fixed cost of posting a SNARK-based proof to Ethereum. But it also means it’s highly scalable.

Scalability

What do we mean by scalability? In a blockchain context, scalability means the marginal cost of transactions goes down with each incremental transaction. The faster the marginal cost falls, the more scalable something is.

In terms of cost, optimistic rollups have no fixed expense, but over a large enough number of transactions, zkRollups quickly overcome their fixed cost disadvantage and win over optimistic roll-ups with superior data compression.

So: zkRollups are more scalable.

Now, if you think about most Layer 1’s, including Ethereum, they’re anti-scalable. The more transactions go through Ethereum, the higher the cost of each marginal transaction.

zkRollups for kids

Here’s a school child’s diagram of the scalability equation for Aztec and other zkRollups:

Must be a really good school if this is what they’re teaching ‘em.

Hopefully this gives you a picture of how Aztec’s path to scaling our own rollup:

  • Reduce the cost of posting a rollup (we control this)
  • Increase the number of transactions per rollup (we mostly control this)
  • Lower the per-transaction cost of posting call data (we don’t control this for Ethereum, but we can select a lower-cost data availability solution)

Let’s tackle these one by one, compare the current system relative to performance a year ago, and discuss what they mean for future network performance.

Cost of posting rollups

In Aztec’s current technological paradigm, an improvement of our proving system called UltraPlonk, the cost of posting a proof to Ethereum is approximately 550,000 gas, ~30% cheaper than it was when zk.money was first launched.

We anticipate this coming down to ~180,000 gas with the advent of our next-generation proving system, [super secret code name redacted].

Transactions per rollup

Our current system was recently upgraded from 112 transactions per rollup at zk.money’s launch to 896 transactions per rollup, an improvement in throughput of 8x.

The way Aztec worked under the hood prior to this most recent upgrade is:

  • A proof is generated client-side in-browser
  • 28 client proofs are then aggregated into an “inner” rollup proof
  • 4 inner rollup proofs are then aggregated into an “outer” rollup proof

That “outer” rollup proof is then verified in what we call the root rollup circuit — the circuit that establishes the validity of all the underlying work that goes into ensuring execution on Aztec happened as expected. Then that final proof gets posted on-chain for posterity.

It’s proofs on proofs on proofs.

For the release of Aztec Connect SDK, we’ve increased the outer rollup’s capacity to 32 inner proofs by optimizing the outer rollup circuit. 28 * 32 = 896. Magic.

That’s why we go through all this headache, writing circuits that can efficiently verify recursive Plonk proofs.

If you’re following so far, the share of rollup costs per transaction fell from:

  • 750k / 112 = 6,700 gas; to
  • 550k / 896 = 614 gas → an 11x improvement!

We think that’s well worth inventing novel forms of cryptography.

Per-txn cost of call data

In addition to the proof, which validates Aztec’s off-chain transactions, Aztec also has to post call data¹ for each transaction, such that anyone can reconstruct the state of Aztec’s rollup and prove the validity of off-chain computation.

Currently, the cost of posting call data to Ethereum is 16 gas per byte. Vitalik has submitted EIP-4488 lowering the cost of call data to 3 gas per byte, while there’s another proposal, confusingly named EIP-4844, which offers a new data format specifically designed to lower the cost to rollups of posting data on Ethereum.

Aztec broadly supports efforts to reduce the cost of data on Ethereum, and we’ll discuss the minutiae of the two EIPs in a separate post.

For now, it’s true for our architecture that scaling costs beyond a few hundred transactions asymptotically approach the cost of call data:

aditi on Twitter: "the result is that even in the case of end users leveraging rollups, posting call data to Eth beholds them to the gas costs they face today as a result of this fixed ratio. modeled below, you'll see that cost will always hit a rough asymptote b/c of fixed call data cost pic.twitter.com/uq9cTYARC4 / Twitter"

the result is that even in the case of end users leveraging rollups, posting call data to Eth beholds them to the gas costs they face today as a result of this fixed ratio.

Note that the chain on which Aztec posts call data is critical for security, because data availability is of chief concern in case Aztec’s rollup provider ceases to function and system state needs to be reconstructed once the provider comes back online.

Note that while a rollup provider going down can only freeze users’ funds in place, with no ability to steal funds, recomputing blockchain state can only happen if state is available (hence data availability).

That’s why for the foreseeable future, we intend to post the rollup’s state to Ethereum–it is for now the Lindy-est, most secure chain with consistent and proven uptime. We’re also excited about exploring our own first-party offchain data availability solution and 3rd-party chains like Celestia.

For now, an Aztec transaction requires the storage of a number of items on-chain:

  • Transaction viewing keys (8,480 gas)²
  • Join-split call data (2,064 gas)³
  • For DeFi transactions, call data for deposit and claim (2,064 * 2)⁴
  • Total: 14,672 gas

Recap & what the future holds

Aztec’s zkRollup has scaled efficiently since the launch of zk.money on mainnet. The impending launch of the Aztec Connect SDK brings up to 100x cost savings for Ethereum DeFi services, all while offering full privacy.

The cost of a private transaction on Aztec will always be cheaper than the cost of a public transaction on Ethereum, despite the added complexity of encrypted transactions — you always get privacy for free (or better than free).

The one elephant in the room is data cost on Ethereum. Call data represents the vast majority (88.8%) of the gas cost for a DeFi transaction. And over time, as proof verification costs fall and the rollup scales further, call data will represent nearly 100% of transaction costs.

At that point, scaling Aztec will also mean optimizing Ethereum.

Next time we’ll cover:

  • Our initiatives to reduce these costs, including taking viewing keys off-chain and pushing for EIP’s reducing the cost of call data on Ethereum
  • How Aztec Connect SDK adds just a little more math to the above

Build with Aztec Connect SDK

Are you a developer who wants to bring privacy to your favorite DeFi protocol? If you build it, we’ll fund it.

Aztec Grants Program: https://airtable.com/shrvglCZ24jaH73oe

Connect Starter: https://github.com/AztecProtocol/aztec-connect-starter.

Help make privacy a no-brainer.

Join the Aztec Community

We’re always on the lookout for talented engineers and applied cryptographers. If joining our mission to bring scalable privacy to Ethereum excites you — check out our open roles.

And continue the conversation with us on Discord or Twitter.

  1. Call data is currently the cheapest form of data storage on Ethereum. It’s a special form of memory used to store function parameters (hence “call” data, because it’s used to call external functions).
  2. Viewing keys are required to view encrypted transactions and read the details of a transaction. Unlike state, they’re not critical for system liveness.
  3. The join-split circuit is a simple formula that ensures Aztec encrypted notes are added (joined) and divided (split) correctly. It follows the simple equivalence (a + b) = (c + d).
  4. The DeFi circuit ensures assets are correctly delivered to the Aztec Rollup (deposited) and returned from the Aztec Rollup (withdrawn).

Privacy for Pennies: Scaling Aztec’s zkRollup was originally published in Aztec on Medium, where people are continuing the conversation by highlighting and responding to this story

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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, an open-source 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. Proofs of transactions on Aztec are settled to Ethereum L1.

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.