Crypto is in a long night. It is no secret that the industry is facing challenging circumstances and there has been a clear consolidation of the industry. Right now we are seeing a focus on real traction, demonstrable value projects shipping practical solutions that will meaningfully reach users. 

Some of that discipline is overdue. However, in times like these the properties that made crypto structurally different begin to look expendable. Decentralization slows you down. It makes upgrades harder. It makes institutional sales harder. It removes the control surfaces that the existing financial world knows how to buy.

We used to accept those costs as the price of building something durable. But, in a famine, they look like unaffordable affectations. Discarding them wholesale, however, is like selling the land out from under our feet.

Permissionless, uncensorable transaction networks with rich composability - this is the clay from which our industry was grown. The long term commercial health of our industry depends on preserving these properties in an age of privacy and institutional adoption.

These trade-offs become more challenging and pernicious when privacy is involved. Privacy is the narrative for crypto in 2026, and for good reason. It’s the missing piece that will deliver the traction and real use-cases that the industry so desperately needs. 

The challenges of decentralization multiply under the constraints of privacy and what we are seeing in the industry is not a pivot, but a complete capitulation of all of the differentiable value that made crypto valuable.

I have spent nearly a decade building a network that marries programmable privacy with decentralization. A network where users keep their data, where applications are composable with one another, where transactions can settle without a privileged party learning everyone’s business or deciding which products are allowed to exist. That required new cryptography, new programming models, new state architecture, new wallets, and a fairly insane number of tradeoffs that are invisible until you try to build the thing yourself. There are easier products to ship. 

A centralized privacy service can give institutions something legible quickly, replicating how the existing financial sector works: a responsible operator, a viewing key, a way to block transactions, a way to explain the whole thing to a risk committee. Some of these products will be useful. Some will be good businesses. But they are not the thing we came here to build.

The Devil’s Bargain

Institutional and enterprise adoption is one of the core growth areas in this crypto-winter and the playbook is simple: use the language of crypto as a skin-suit to sell products and services that pattern match onto existing financial rails, with their need for complete visibility, censorship, centralized network operators and all of the liabilities this incurs.

This is a tempting bargain because it shortens the path to adoption. It gives buyers and regulators a shape they understand. A company. A contract. A switch. But the moment you accept that bargain, the system changes character. It may still be encrypted. It may still contain proofs. It may still call itself private. But, it now behaves like and is an operated service. 

There is a party with privileged knowledge and privileged control. Builders must shape themselves around it. Institutions negotiate with it. Regulators may pressure it. Attackers target it. Users ultimately depend on it. By a backdoor I mean something specific: a network or protocol-level viewing key where the product developer does not control who can see their users’ data, especially when paired with network-level controls that can block transactions or ban smart contracts entirely. I do not mean application-level controls. I do not mean user-authorised disclosure. I do not mean a dapp deciding that users must prove something before using it. Regulated applications will need rules. The issue is that the disclosure boundary of your application belongs to somebody else, and the same layer that sees can also decide whether your users are allowed to transact. In short, users lack a platform that has credible neutrality.

The Platform Risk

Privacy on top of centralized rails is fatal. If one party can see everything and stop anything, that party may be treated as responsible for seeing and stopping.

This compounds into substantial platform risk. If an entity builds on top of such a system they must surrender visibility and control to the network operator to satisfy their liabilities without consideration for yours. Decentralization and ultimately credible neutrality is the difference between whether you own durable infrastructure or are renting a service whose rules can change on a whim. Worse, you cannot “just build things”. For novel transaction flows approval must be sought and granted. Tell me, would Ethereum have grown if every smart contract deployment required approval from the Ethereum Foundation?

Privacy needs the same freedom. A private credit market, for example, touches identity, collateral, repayment history, payment flows, liquidation logic, lender disclosures, auditor access and borrower privacy. If every component lives inside a different permissioned service, each with its own operator and viewing assumptions, that is a bureaucratic friction that negates blockchain’s core value proposition; composability.

A decentralized and credibly neutral privacy network prevents the settlement layer from becoming the single place where all surveillance and censorship obligations naturally accumulate. It allows product developers to scope their code to satisfy their own narrow requirements without consideration for the obligations of a centralized operator.

Building for credible neutrality

A lot of today’s privacy narrative treats architecture as if it were a detail. It is not. You cannot take a transparent ledger, staple confidentiality onto the edge, add a viewing key for comfort, and expect to get programmable private infrastructure.

If the state model is not private from the ground up you get wrappers, third party tools, data custodians, ad hoc disclosure paths and a pile of assumptions that every application drags into the next. Developers do not get a normal programming model where private contracts can call private contracts and users keep state on their own devices. They do not get composability.

The difference matters. In a real private execution environment, users generate transactions locally. They do not outsource their intent to a third party who learns what they are doing. Private contracts interact through a state model designed for privacy. The network settles proofs without becoming the party that knows everyone’s business. Privacy is part of the architecture.

This is why Aztec has taken so long. We built something that makes programmable private state and decentralised settlement live inside the same system. That means proving systems that run on consumer hardware, a transaction architecture built around local private execution, and a programming model where privacy is idiomatic and just works out of the box.

A centralized service can skip much of this. It can hold the key, run the prover, approve the flow and call the result privacy. It gets to market faster because it is not trying to arrive at the same place.

The edge

Adding decentralization does not make obligations disappear. Applications, issuers, frontends, custodians and regulated businesses will continue to exist in a web of obligations and responsibilities. Anyone pretending otherwise is unserious.

The question is where those obligations live. If they are pushed into the settlement layer, the settlement layer is no longer credibly neutral. It needs visibility into everyone and controls over everyone. 

The better answer is selective disclosure. Users and applications should prove specific facts to specific parties for specific purposes. A regulated application may need to know that a user passed a check, that a transaction satisfies a policy, or that an auditor can inspect a particular flow. None of that requires the base network to hold a permanent key into everyone’s activity.

This will be harder to explain to the existing world. New infrastructure always fails to fit the categories built for the old infrastructure. Bitcoin did not arrive as a neatly regulated bank product. Ethereum did not wait for every lawyer to understand smart contracts. Stablecoins and DeFi forced institutions, regulators and users to develop new language around rails that kept existing.

If the standard for privacy infrastructure is to plug into the old world without changing anything, the answer will always be a service with a backdoor. And the result will be to catch crumbs falling from the tables of the old world.

The market worth building

The market we should be building is, well, a market. A private financial system that compounds: assets, liquidity, identity, credentials, credit and applications interacting through a shared settlement layer without forcing users to surrender their data to whoever sits in the middle. 

Traditional finance is built out of vertically integrated information silos. Those silos are its moat. Banks, exchanges, custodians, payment processors and data brokers all benefit from controlling the information that flows through them. A global private settlement layer attacks that advantage directly. It lets liquidity and credentials move while outsourcing information custody to neutral cryptographic infrastructure. 

A company wants a moat. A settlement layer wants surface area. A permissioned privacy provider can ration access, raise fees, exclude applications, shape disclosure rules and define acceptable use around its own risk tolerance. These are products pretending to be networks, and not durable financial infrastructure. What bothers me is this compounding category confusion. Networks adding protocol-level viewing keys and transaction controls are using the same language as decentralised programmable privacy, and commentators are treating them as variations of the same thing. They are not.

We have spent nine years walking the hard road. Now, just as we are close, the market has lost faith. Everyone is reaching for whatever lifeline looks immediate. Some of those lifelines will be real. Some will make money. But if crypto responds to its long night by rebuilding financial privacy as permissioned services, then we will have survived by surrendering the property that made the industry worth building.

Markets can grow when the platform is removed from the position where it can dictate the rules. It would be perverse to forget that lesson while building privacy, the domain where control over information matters most.

The land we till

Crypto is in a famine. The land is struggling. We could sell our land for a pittance and survive the season. But the famine will pass, and when it does the land will blossom again. Without the land we are nothing.

We have struggled immensely to create a permissionless network that can marry privacy with decentralisation: an indestructible network whose users cannot be surveilled and whose transactions cannot be censored. This is the soil we have to grow our crops. To surrender a backdoor or a centralized operator for temporary relief is to sell our land for the price of a stablecoin. And we cannot sell the land.

‍
Follow Zac on X to get more insights
Follow Aztec on X for updates & breaking news

Privacy has become a baseline requirement for L1s and L2s who care about bringing real-world users onchain. Users don't want their activity broadcast to competitors or the general public, but applications operating at scale also need some form of auditability, whether for regulators, compliance requirements, or tax reporting. Selective disclosure resolves that tension: privacy by default, with the ability to prove specific facts when required. What separates these networks is not whether they offer that switch, but who gets to hold it.

Aztec, Canton, Starknet, Tempo, and zkSync all offer some form of privacy with selective disclosure, but under the hood they make fundamentally different architectural decisions about who can see your data and who can turn your privacy off. Those decisions determine whether your privacy stays under your own control or sits behind a switch that someone else operates.

Three questions reveal where these networks actually diverge:

1. Who sees your data?
2. Who can prove the network followed its own rules?
3. Who controls when something gets disclosed?

The answers determine whether your privacy off-switch is held by a policy, by an operator's good behavior, or by you alone through a cryptographic proof. As you'll see in this post, there are legitimate reasons to use each one with different tradeoffs. Aztec is the only network, however, where that switch stays in the user's hands, answering all three questions without putting a permissioned set of operators or a standing viewing key in control of your privacy. That gives developers the flexibility to build apps that comply with applicable laws while still keeping full privacy under the user's control.

This article will compare the privacy approaches of Aztec, Canton, Starknet, Tempo, and zkSync to give developers insight into the privacy tradeoffs of each network.

TL;DR

Here’s how each network handles the selective disclosure privacy off-switch, and who has control over your privacy: 

• Aztec: Only you can see your data, client-side proofs settled to Ethereum let anyone verify every transaction without trusting an operator, and the off-switch stays in your hands, allowing you selectively share information.
• Canton: Participant nodes read your data in plaintext, no outside party can verify the global ledger, and your off-switch sits with those nodes rather than with you, since disclosure depends on them staying honest.
• Starknet: No operator ever sees your plaintext because proofs are generated client-side, and those proofs verify the rules, but your off-switch is a standing viewing key that a designated auditor can use to decrypt and trace your entire history on request.
• Tempo: The zone operator sees every transaction in plaintext, mainnet validity proofs let anyone verify the zone ran correctly, and the operator holds the off-switch, so you are private from the public but not from the operator.
• ‍ zkSync: The operator reads every transaction in plaintext while a validity proof on Ethereum proves it cannot forge state, and the operator holds the off-switch over who sees what, giving you privacy from the outside world but not from the operator.

The Comparison In One View

‍

Comparing your privacy off-switch 

Each of these networks offers privacy with selective disclosure, but each rests on a different network design with its own tradeoffs. We have ordered them by who holds your privacy off-switch, starting with designs where a third party controls access to your data and ending with designs where that control stays with you. At the top, the switch sits behind a policy promise and an honest operator, and further down it is replaced by proofs that the user generates and controls.

‍

Canton

Canton keeps data private by controlling viewing permissions for the various actors on its network. A transaction splits into per-participant views, so each party receives only the sub-transactions that name it, and the parts it is not entitled to never reach it. The sequencer and mediator move those views without reading them, which is real privacy against those roles.

However, the data is still read in plaintext by the participant nodes that host the relevant parties, and in the common regulated-asset pattern where the issuer is a signatory on its own token, the issuer's node sees every transfer. The harder gap is verification, because no third party can reconstruct the global ledger, so correctness rests on the confirming nodes staying honest and their keys staying safe. In practice the off-switch sits with those nodes rather than with you, since you cannot see when your data is read and cannot stop it.

‍

Tempo

Tempo is designed for payments and uses validity proofs to verify that each zone is executing correctly, while still giving the zone operator full plaintext visibility into every transaction within that zone. Privacy comes from Tempo Zones, which are parallel execution environments connected to the Tempo mainnet.

By design, the zone operator has visibility into all transactions within the zone, while users see only their own and the public sees only a proof that the zone is valid. Token issuers set compliance controls, allowlists, blocklists, and freezes, enforced across zones. The mainnet checks each zone's validity, so execution is verified, while the operator still reads every transaction in plaintext and holds the off-switch over what is revealed. Your privacy is from the public, not from the operator.

‍

zkSync Prividium

zkSync Prividium adds the verifiability piece that Canton lacks. Every batch produces a validity proof settled to Ethereum, so a compromised operator cannot forge state or mint tokens from nothing without also forging a proof, which it cannot do. The tradeoff is that the operator processes every transaction in plaintext and decides who sees what, which means the off-switch stays with the operator and your privacy is from the outside world rather than from the operator itself.

This tradeoff has legitimate uses in high-trust institutional environments. If Bank of America, JPMorgan, and Wells Fargo are transacting on a shared network, a zone where BofA's infrastructure processes BofA-originated transactions satisfies internal control requirements while still delivering genuine ZK privacy from the other banks and the rest of the world. Where this model breaks down is in lower-trust environments where giving an operator full plaintext access and the switch that comes with it holds back product design possibilities. 

‍

Starknet STRK20

Starknet's STRK20 breaks from relying on an operator for privacy. It shields ERC-20 balances and transfers in a privacy pool, and every private transaction carries a zero-knowledge proof generated client-side, so no operator sees your plaintext in order to build it.

Disclosure is where STRK20 diverges from Aztec. To join the Starknet Privacy Pool, you register an encrypted viewing key onchain, and it sits there for the life of your participation. On a regulatory request, a designated auditing entity can decrypt that key and trace your complete transaction history, forwards and backwards. StarkWare calls this ‘not a backdoor’ but a carefully scoped access mechanism, and the safeguard is a policy promise that the auditor decrypts only when required. The privacy is cryptographic, but the off-switch is a standing key that someone else holds and can flip whether or not you are watching.

‍

Aztec

On Aztec your private state lives as encrypted private data that only you can decrypt. The contract developer can choose what state is public and what is private, and whether your encrypted private data is emitted onchain as a private log or shared off-chain instead.

Your transactions get proven client-side on your own device, so no sequencer or operator sees your unencrypted private data. Those proofs settle to Ethereum, which gives the same integrity anchor marketed by Prividium, with every transaction verified and no forged state, but without a single operator who reads your data. The base protocol decentralizes sequencing, proving, and governance, so there is no operator to choose and trust in the first place.

Disclosure is your choice too: you decide who learns your private data, and whether they learn it in encrypted or decrypted form. To grant discovery without readability, you share an app-specific tagging secret that lets an auditor find your data in encrypted form without being able to decrypt and read it. This is enough to prove things calculated from that data, such as a tax basis or a profit and loss figure. Granting permission to actually read the data works differently. There's no per-contract read key you can hand out, because decryption uses your master viewing key, which would unlock all your data across every contract. So instead of sharing a key, you share the data itself, plus a proof that your plaintext is what encrypts to the on-chain ciphertext.

Aztec has true selective disclosure in that you can selectively share it, and nothing else you don’t need to. This is app specific, meaning that private data discoverability access on one app does not grant access on another. Most importantly, the off-switch stays in your hands, and you never need to trust the network to handle access to any of your private data and activity.

This is not just conceptual: here is a working proof-of-concept of this model on Aztec. PrivPNL takes you from private DEX trades through a tagging-key disclosure to a browser-generated ZK proof of your PnL. The auditor verifies a proof while the prover only has to reveal the amount they owe, and your portfolio stays private.

‍

Users need to hold their own off-switch, not a promise to look away

Canton keeps the switch with the participant nodes that read your data in plaintext, so disclosure rests on those nodes staying honest rather than on anything you control. Tempo similarly gives the off-switch to a zone-based node operator, but allows you to verify the correctness of transactions using validity proofs. Prividium hardens that promise with a proof settled to Ethereum, a real improvement, but the operator still reads every transaction and still decides who sees what. This can work well for large institutions, but small to medium sized enterprises are left with the same privacy as their current banks unless they run their own Prividium nodes. STRK20 moves the switch into a standing viewing key and asks you to trust that a designated auditor reaches for it only when needed. In each of these models the real question is not whether your privacy can be switched off, but who gets to do the switching, and whether you would even know it happened.

Aztec takes the operator and the standing key out of the question entirely. You keep the data, you generate the proof, and you disclose the result, one fact at a time and only when you choose to. The off-switch never leaves your hands, and no operator, auditor, or node can reach it on your behalf. This is one of the benefits of a network that offers fully programmable, privacy-preserving smart contracts that put you in control. 

Selective disclosure is how privacy survives contact with a regulator, and the model you pick decides who can open your history when you are not looking. On Aztec, that answer is no one but you.‍

‍

Let's Build

Dive into the technical details: Try a live demo of selective disclosure on Aztec and read the technical article on how it was built. 

‍Integrate with Aztec: Reach out if you are interested in integrating privacy into your project.

Aztec is built on one idea: smart contracts on Ethereum where developers choose what is public and what is private. That doesn't just mean shielded transactions. It means who acts (identity), what they transact (state), and how they execute (computation) can all be private. Aztec makes end-to-end privacy possible; even the contracts themselves can be private.

But privacy also has to be practical. Aztec integrates private and public execution in the same contract, so apps can seamlessly weave together private and public state. Every account is a smart contract, letting users grant granular, revocable access for selective disclosure, which is useful for compliance, tax reporting, or agent permissions.

Finally, Aztec is a decentralized L2, with 3,500+ sequencers participating in the network today. That permissionlessness is what makes Aztec a credible foundation for a global privacy layer.

In this article we’re going to explore the Aztec stack and how we make programmable privacy a reality. We’ll answer questions like ‘what can you do on Aztec?’, ‘how does it all work?’, and ‘what are the core layers of the system that makes it all possible?’

‍

TL;DR

The four layers of the Aztec stack, all live today on the Alpha network: 

1. Noir: a programming language for writing private programs with simple, familiar syntax. 

2. Aztec smart contracts: written in Noir using the Aztec.nr framework, allowing you to easily write smart contracts with both public and private state. 

3. Aztec Network: a fully decentralized, privacy-preserving Ethereum L2 for building useful applications. Private state uses a UTXO model, public state uses an account-based model like Ethereum. 

4. Ethereum: L2 txn rollup proofs are stored on Ethereum, inheriting strong economic security. 

‍

Layer 1: Noir, the Universal Language of ZK 

Aztec smart contracts are written in Noir, a programming language with Rust-like syntax optimized for writing private programs. Noir is an open-source project developed by Aztec and is now the industry-leading language for writing private apps using zero-knowledge proofs. Let’s dive into what Noir is, and why we use it as the building block for writing smart contracts. 

Writing zk programs is extremely difficult without a background in cryptography. When developing Noir, our first goal was to create a highly optimized and easy-to-write zk Domain Specific Language (zkDSL) where developers don’t need to know any of the underlying mathematics. As a result, Noir handles all the cryptographic complexities, and will automatically convert your code into fancy zk circuits. 

‍

Noir compiles down to the Abstract Circuit Intermediate Representation (ACIR), an adaptable intermediary language that makes it easy to plug in a variety of popular proving backends. These proving backends, such as Aztec’s Barretenberg proving system, take the compiled zero-knowledge circuits and generate proofs attesting to the validity of the program’s execution, all without revealing any private inputs. From authorization systems that keep a password on the user's device, to complex onchain state channels with recursive proofs to verify offchain state; Noir and a proving backend handle everything from compilation to cryptography for you. 

In addition to simplifying the developer experience, we also wanted to make it intuitive to specify which elements you want to keep private and which you want to make public. With Noir, privacy is baked in as a default, so all variables and functions are automatically kept completely private, and executed on the user’s device. 

If you want to make any part of your code public, you can do so by simply adding a pub attribute. 

‍

‍

Noir on its own is great for writing programs that need to execute stateless functions, such as proving that you reside in a specific country based on passport data, or that you hold a certain number of tokens without revealing how many. Projects are already starting to build with Noir outside of Aztec on Base, Scroll, Starknet, and other chains. However, if you are looking to write privacy-preserving apps that store private state data onchain, it’s helpful to utilize a smart contract library that deliberately handles those complexities for you. That’s exactly what we’ve built at Aztec and what we’ll explore in the next section. 

Layer 2: Smart Contracts 

‍

Aztec smart contracts leverage Noir to create apps with onchain private and public state. This section covers how smart contracts work on Aztec and how you deploy and interact with your contracts. 

An Aztec smart contract is a set of public and private functions written in Noir, deployed on the Aztec Network. They are written using the Aztec.nr framework which handles all the cryptography under the hood for managing private and public state and interacting with other contracts on the network. 

To build useful applications, developers need to be able to incorporate both private and public components into their contracts. For example, an onchain voting contract might want to keep the information of the voter private and prevent someone from voting twice, but publicly display how many votes have been cast, and the outcome. 

Because contracts are written in Noir, this functionality is as easy as adding a ‘private’ annotation above your function. The following function will be executed privately on the user device, allowing a user to cast a vote without revealing their address: 

‍

‍

The output of this private, local execution will be sent to the network, where the correctness of execution is verified and public function calls are executed. The following function is designed to be executed publicly, adding a vote to the total tally without revealing where it came from. 

‍

‍

To seamlessly weave together private and public components that can easily interact with onchain state, Aztec smart contracts utilize the Aztec.nr framework to execute private functions on the user’s device and bundle the proofs for these transactions together with the public functions that will be executed by the Aztec Virtual Machine (AVM). 

This framework adds the functionality needed to build onchain, privacy-preserving apps, including defining contracts, accessing private or public context, and interacting with the Aztec Network. Similar to how a vanilla Noir program would compile down into zk circuits, Aztec smart contracts are compiled into zk circuits for private functions or AVM bytecode for public functions, and stored in the Aztec contract tree. 

Aztec accounts are also written as smart contracts, implementing what is known as account abstraction. Account abstraction allows application developers to create programmable accounts to dramatically improve user experience, including social recovery, sponsored transactions, and multi-factor authentication. It also makes compliance practical, allowing for granular access controls on accounts. 

‍

Layer 3: The Aztec Network

The Aztec Network is the only decentralized L2 on Ethereum. There are currently over 3,500 sequencers running the alpha network. View the live block explorer for the alpha network. 

In order for a network to fully protect users and their data, it must guarantee three levels of privacy: 

• Private data: input and output values are hidden

• Private identity: addresses are hidden 

• Private compute: contract functions are hidden 

When you write  Aztec smart contracts, everything listed  above is taken care of for you. As discussed in the previous two sections, you can easily opt into privacy protections at a granular level by weaving together public and private functions. 

To understand how all of these components fit together, let’s examine how a transaction is executed on the Aztec Network. 

‍

‍

When a user interacts with your application, private functions are executed client-side on the user’s device: a phone, a personal computer, etc. This happens in a private execution environment (PXE) that is able to create highly-efficient zk proofs even on browsers and mobile devices. Any private state updates are added to the state of the network in an append-only database (UTXO tree). Because the proof is generated client-side, no information can be leaked about the inputs, outputs, accounts, or even the functions that were executed.

On the other hand, public transactions are bundled together with the private client-side proofs and sent off to the Aztec Network, powered by a decentralized network of independent community-run sequencers. Sequencers check the validity of private execution proofs, execute any public functions and update the public state, propose blocks, and publish state updates (“diffs”) to Ethereum L1. Sequencers also coordinate with a decentralized network of provers who compute the final proof for every Aztec “epoch” - defined as a contiguous sequence of 32 L2 blocks - and publish it to Ethereum. Any public functions executed by sequencers update an account-based database similar to Ethereum. 

Sequencer and prover roles are fully permissionless. Anyone can spin up the required hardware and join the sequencer set or run provers and start bidding to produce proofs of Aztec epochs. 

‍

Conclusion

Aztec delivers on a simple but powerful idea: smart contracts on Ethereum where you choose what's public and what's private across identity, data, and compute. The four layers we've walked through are what make that possible.

Noir gives developers a Rust-like language for writing zero-knowledge programs without a cryptography background, with privacy as the default. Aztec smart contracts build on Noir through the Aztec.nr framework, letting you weave private and public functions into a single contract and use account abstraction to unlock granular access controls for compliance, tax reporting, and selective disclosure. The Aztec Network is the only decentralized L2 on Ethereum, with over 3,500 sequencers powering end-to-end programmable privacy across data, identity, and compute. And it all settles to Ethereum, inheriting L1's economic security.

The result is the first practical platform for privacy on Ethereum, and a credible candidate to become the global settlement layer of the future.

Now it's your turn to build. Head to docs.aztec.network to ship your first privacy-preserving app.

Follow Aztec on X for updates on the current state of the network. 

‍

Last week, PSE published an insightful and comprehensive user-research piece on private transfers on Ethereum. They interviewed 38 teams in the space and asked what's broken, what's missing, what builders wish they had. The list reads like a wishlist of features every privacy app on L1 is currently trying to engineer towards. It's the kind of rigorous, builder-grounded research the privacy ecosystem has needed.

We read the list. It's the list we've been building against for years.

Aztec solves all of these problems. Every requested feature already lives on Aztec. The proving system, the private contract language, the decentralized network, the privacy wallet architecture, the key model, the snark-friendliness: all of Aztec was built against this list before it was a list.

What follows is a walkthrough. For each of PSE's top technical findings, here's the feature builders are asking for, and how it works on Aztec today.

TL;DR

1. Slow client-side ZK proving: Aztec's client-side proving system (Chonk) is optimized specifically for fast recursive proving on resource-constrained devices such as phones (and even in the browser).
2. Expensive L1 proof verification: Aztec amortises the gas costs of L1 verification across thousands of users per rollup. Instead of “millions of gas per user” it costs hundreds of gas; that’s pennies per user transaction.
3. DeFi composability with private state: Private token contracts on Aztec can be unshielded to easily interact with Ethereum DeFi contracts, and the resulting state can be shielded, without leaking who did the interaction. Or you can just design composable private DeFi contracts within Aztec.  
4. Deposit/withdrawal leakage: Aztec isn’t a basic shielded pool, so users don’t need to keep withdrawing to do useful things. Users can use their funds within private smart contracts. Privacy leakage doesn’t happen if all transaction activity stays in private-land.
5. No native wallet support: Of course Ethereum wallets don’t natively support privacy; Ethereum doesn’t have native privacy. There are a huge number of new concepts that are needed to design a private smart contract wallet. Aztec wallets are built from the ground up to enable a rich private onchain experience. 
6. Reliance on external networks, TEEs, FHE, and relayers: The private and public execution environments of Aztec aren't reliant on external networks. Aztec is a fully decentralised L2, without these centralisation concerns. 
7. Keccak is inefficient inside ZK circuits: The entire Aztec protocol uses Poseidon2, so complex private txs are rapid to prove on a phone. 
8. Slow private state sync: Brute-force scanning of the entire chain’s history is not necessary. Aztec's tagging scheme lets recipients pinpoint their notes in seconds from a shared secret.
9. Fragmented privacy sets: All private smart contracts on Aztec share one global note tree and one global nullifier tree. All network activity contributes to and draws from a single privacy set.
10. No tooling or standards for private contracts: Aztec has a huge suite of tools to ship private contracts. Noir, a smart contract framework, a private state manager, a keystore, the PXE for executing contracts locally, a JS SDK, testing frameworks, local test networks, a CLI, and a slew of advanced private contract standards.

1. ZK proof generation time on user devices

Ethereum Problem: Proof generation is too slow on user devices, especially mobile. Elliptic-curve pairing operations are a specific bottleneck. Server-side proving is a censorship and privacy leak vector. Sub-second proving was the stated threshold.

Aztec solution: Proving on Aztec runs locally in the PXE (Private eXecution Environment, pronounced "pixie"), so no data ever leaves the user's device. Chonk, our client-side zk proving system, is ruthlessly optimised for fast recursive proving on low-memory devices like phones, native and in-browser. Years of optimization have already gone in, and we're still finding more. It’s best in class and we haven’t even merged-in GPU acceleration yet!

The slow pairing checks that PSE's interviewees called out as a bottleneck aren’t a problem with Aztec; pairings are simply batched together and deferred away from the user's device, handled by the more powerful network instead, without leaking any information. With such a powerful local prover, there’s little need to outsource proving to an untrusted party.

2. ZK proof verification gas on L1

Ethereum Problem: Verifying a ZK proof on Ethereum is prohibitively expensive. A Groth16 proof for a private transfer costs several hundred thousand L1 gas. A Halo2 (KZG Plonk) proof can cost approximately one million gas

Aztec solution: Aztec amortises L1 verification gas across all transactions in the rollup. At current network throughput, that cost is split across roughly 2,000 users per proof. Later this year, it’s slated to be split across ~20,000. Rollup costs are also partially subsidised by Aztec block rewards.

Net result: hundreds of L1 gas per user instead of millions. Plus cheap L2 gas. The user pays pennies for an Aztec transaction.

3. DeFi composability with private state

Ethereum Problem: Wrapping and unwrapping tokens leaks privacy and breaks composability. Smart contracts can't easily interact with encrypted balances. Private state is isolated; contract state is normally shared.

Aztec solution: Private state is not isolated on Aztec. The private state of one contract can be composed with that of another. This can unlock new privacy-preserving DeFi patterns directly on Aztec.

A single private transaction can call a stack of private functions across multiple contracts, with private inputs, private state transitions, and privacy over which functions were even executed and how many. Observers see that a transaction landed. They do not see what happened inside it. Stew on that for a second: a call stack of nested private functions across contracts written by different developers, each causing state transitions, all completely private.

Aztec also runs public functions, similar to Ethereum, inside the same smart contract, so you can build existing DeFi primitives on Aztec. 

For Ethereum DeFi specifically, Aztec has a tidy L1-to-L2 messaging layer. Private balances can be unshielded to interact with L1 protocols and shielded back, without leaking who did the interaction and without leaky public gas payments. And for private DeFi primitives that need genuinely shared private state (state nobody knows the value of, but which anyone can mutate), people have built Aztec contracts that compose conventional Aztec private state with co-snark or FHE sidecars.

Private and public state are peers inside a single Aztec smart contract. Builders mix and match.

4. Deposit/withdrawal privacy leakage

Ethereum Problem: Entry and exit points are the dominant privacy leak, not the protocol itself. Depositing and quickly withdrawing makes identity analysis trivial.

Aztec solution: The main fix is to stop crossing the boundary so often. (Or even if you do cross the boundary, Aztec has leakage protections).

Imagine if thousands of private smart contracts lived on the same network and could call each other without leaking which contracts were called, which arguments were passed, or what was returned. Imagine they all shared one global note tree and one global nullifier tree. That's Aztec. Once funds are inside, users don't need to keep crossing the private/public boundary to do useful things: Aztec is its own rich environment for composable, private execution of smart contracts.

Even when a private function does need to call a public function – be it an L1 DeFi contract, or a native public function within Aztec – the developer controls the information they reveal; not the protocol. The call can even be "incognito" to hide msg_sender. A single environment for many private apps to thrive also means re-usable tooling for builders.

5. Lack of native wallet support

Ethereum Problem: Privacy features (per-dapp addresses, private transfers) aren't natively integrated into major wallets. Reliance on dapp-specific UIs damages UX.

Aztec solution: Ethereum wallets weren't built for any of this, and they don't need to be: the chain underneath them has no private state to protect. Aztec wallets are an entirely new category of software.

Aztec wallets are able to manage all these new privacy-centric concepts:

• Authorize your transactions however you want, without revealing your identity to the world. Native account abstraction lets you choose any auth scheme you like, and that choice doesn't expose who you are.
• Hold multiple specialized privacy keys. Distinct nullifier, viewing, and efficient message-signing keys.
• Keep your full private state on your own device. An encrypted local database holds your notes and nullifiers (siloed by private contract address), along with private data, private messages, shared secrets, and private contract bytecode.
• Fine-grained contract access control for your private data.. Access permissions for contracts to read your private data are granular and revocable, rather than all-or-nothing.
• Run private contracts without cross-contract interference. Built-in protections can stop malicious private contracts from reading or manipulating the private state of other contracts.
• Establish shared secrets with your counterparties. Wallets can support both on-chain and off-chain methods for setting these up.
• Catch privacy leaks before you sign. Pre-flight transaction privacy analysis warns when your data might be leaked via public args, msg_sender, fee payment, or even through the shape of the tx.
• Make your tx look like every other tx on the network. Random padding is added to notes, nullifiers, and logs, and gas settings, anchor blocks, and inclusion deadlines are randomized so every tx blends in with the crowd.
• Submit transactions privately to the network. Txns can be submitted to the network through a private submission path.
• Pay fees through generic private fee paymasters. This gives users convenience and enables experimentation over the best private token contract designs for different use cases.
• Use your wallet to gatekeep which frontends can access which private data . Apps shouldn’t have unfettered access to everything; a wallet needs to protect users’ private data..
• Get post-quantum hygiene warnings. Wallets are able to flag risky patterns around address reuse and ephemeral-key broadcasts.

Aztec wallets are in active development, and this is an area where we expect many teams to build different wallets that are customized to various user needs. An early wallet is already baked into the protocol for developers to start using today. 

6. Reliance on relayers, FHE coprocessors, and TEEs

Ethereum Problem: Encrypted tokens and many privacy protocols depend on external networks for encryption, decryption, or relaying. Threshold-decryption committees and TEE hardware vendors are added trust assumptions on top of the chain itself.

Aztec solution: Aztec's private and public execution environments are not reliant on external networks. Aztec is its own decentralised network: ~4,000 validators stake on it, block proposers are randomly selected, a random committee attests, and a decentralised set of provers proves the rollup's execution. Validity is ultimately backed by cryptographic proofs settled on Ethereum.

External networks (co-snark networks, TEEs, MPC or FHE sidecars) become an opt-in choice for the specific case of private shared state. The trust tradeoffs there are something the contract developer signs up for explicitly, not a tax every user pays on every transaction by default.

7. Hash function inefficiency inside ZK circuits

Ethereum Problem: Keccak is inefficient to prove inside ZK circuits. There is no native support for a ZK-friendly hash like Poseidon.

Aztec solution: Poseidon2 is enshrined across the entire Aztec protocol, for rapid proving of every tx. Every Aztec state tree, the proving system, the innards of the protocol; everywhere. Reading and writing state inside a circuit is as cheap as it gets.

Keccak, SHA, and Blake hashes are still available through optimised Noir libraries when contracts need them for L1 interoperability. The default is ZK-friendly; the L1-friendly hashes are there when you reach for them.

8. Private state synchronisation

Ethereum Problem: Syncing private state (scanning for incoming notes and events) is a client-side bottleneck. Users wait for scans to complete before seeing their balance. Tachyon-style oblivious sync was cited as a path forward.

Aztec solution: Brute-force syncing of private state is rarely needed. Most real-world use cases involve a sender and recipient who can establish a shared secret offchain first.

From that shared secret, both parties can derive a sequence of random-looking “tags”. Each encrypted note log is prepended with the next tag in the sequence. The recipient already knows the next tag, so they know exactly what to query. Note discovery happens in seconds, not minutes. The scheme slots cleanly into PIR or mixnet approaches for extra privacy on the query itself, and smart contracts that don't trust senders to use the correct tag can just constrain it inside the circuit.

That’s not to say that Aztec requires interactivity between all senders and recipients. For genuinely non-interactive use cases (recipient can't talk to the sender before the transfer), Aztec enables devs to customize both their log emission and their note-discovery logic however they like. (Aztec also has ways to speed up the brute-force scanning approach from "scan the whole chain" to "scan a tiny subset of non-interactive handshake txs"

9. Fragmented privacy sets

Ethereum Problem: Shielded pools are fragmented across dapps and chains, reducing the effective privacy set for all users. Each new privacy protocol must bootstrap its own.

Aztec solution: There is one global note tree and one global nullifier tree on Aztec, shared by every smart contract on the network. Every private app contributes to and draws from the same privacy set. No per-app bootstrap. No walled gardens.

Private payments, private swaps, lending, payroll, treasury, identity attestations: all of them land in the same global commitment set, by construction.

10. Tooling and standards for private contracts

Ethereum Problem: Ethereum developer tooling lacks support for private transfers and private state. Standards for private tokens, compliance, and wallet interactions are missing. Many privacy teams are small, with short runway and expensive audits.

Aztec solution: Aztec ships the full toolchain for private contracts: Noir for writing private logic, the Aztec smart contract framework with macros that hide the protocol mess so devs can focus on app logic, the PXE for keys / state / syncing / proof generation, a JS SDK, a local node for testing, a CLI, and a real, live, decentralised L2.

The mental overhead of building a privacy protocol on Aztec collapses to "just write the app logic." Here is an example of a complete private transfer function on Aztec:

‍

#[authorize_once("from", "authwit_nonce")]
#[external("private")]

fn transfer_in_private(from: AztecAddress, to: AztecAddress, amount: u128, authwit_nonce: Field) {
    self.storage.balances.at(from).sub(amount).deliver(MessageDelivery.ONCHAIN_CONSTRAINED);
    self.storage.balances.at(to).add(amount).deliver(MessageDelivery.ONCHAIN_CONSTRAINED);
}

Look at how simple that is.

A two-line function body.

Two lines.

Aztec takes care of the rest.

Behind those #[...] macros, the framework handles: caller authorisation, note syncing, fetching notes from the user's private db, Merkle membership proofs against the global note tree, safe nullifier creation (without leaking master secrets to the circuit), randomness for new notes, encrypted ciphertext generation, log tagging for fast recipient discovery, and public-input population. The PXE handles key management, private state, and proof generation. The smart contract itself contains its own message-processing logic for log discovery, decryption, and storage on the recipient side.

If you want whitelists, blacklists, association sets, custom tx authorisation, viewing-key hierarchies, temporary view access, selective disclosure to specific counterparties, just import a Noir library. Want something more adventurous than private payments? Same toolchain. 

What this adds up to

PSE's findings are not ten unrelated bugs. They're the same problem refracted ten ways: privacy retrofitted onto a chain that was not designed for it yields bad tradeoffs. 

Aztec was designed against this list before it was a list. One global note tree and one global nullifier tree. Private and public state inside the same contract. Compose calls between private contracts without leaking anything. Fast client-side proving on phones via Chonk. Snark-friendliness everywhere. Rollup-amortised L1 gas costs, fractions of a cent per user. Native account abstraction with private fee paymasters. No painfully slow private state syncing: a tagging-based note discovery scheme that runs in seconds. An entirely new category of wallet that treats privacy as a first-class concern. Simple, high-level smart contract syntax that collapses a basic private token transfer function into two lines.

There were 10 privacy features Ethereum devs wanted, all of them live on Aztec. The infrastructure is in place. Build the thing.

Go to our docs to start building. 

Aztec is the blockchain that solved the privacy problem. Start at docs.aztec.network or read the architecture deep-dive on The Best of Both Worlds: How Aztec Blends Private and Public State.

‍