Aztec Network
22 Nov
## min read

Infinite Privacy: New Anonymity Paradigms with Aztec Network

Discover how Aztec Network's latest privacy paradigms redefine anonymity, offering unprecedented privacy levels in the blockchain world.

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Written by
Jon Wu
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Endlessly expanding privacy sets with Aztec Network.

In the last article in our series on Aztec’s privacy architecture, we explored how a private network is even possible on a public blockchain.

Today we’re exploring why a private network can be private and compliant.

Aztec offers basic deposits and withdrawals — meant to provide consumer privacy to Ethereum users: our current private payments front-end zk.money has been live on mainnet since March and recently crossed 4,800 ETH in deposits bridged.

But zk.money also offers private internal transfers and will soon offer a full suite of Ethereum Layer 1 Defi functionality enabled by our bridge, Aztec Connect.

The addition of DeFi functionality means Aztec will offer a large and dynamic privacy set that will become increasingly more complex and privacy-protecting—a concept we like to call Infinite Privacy.

The Infinite City

Imagine Aztec as a walled city. All an outside observer can see is users entering and leaving Aztec via our bridge.

Within the walls of the city, users can exchange assets with fully private transactions. Neither the network nor its participants can see the senders and recipients of transactions, nor their amounts.

Tenochtitlan, the capital of the Aztec Empire. With credit to http://joelgehringer.com/blog/the-city-of-dreams/.

In addition, once inside the system, users can batch transactions and teleport back to L1 — to swap, stake for yield, lend funds, vote in DAOs, or buy NFTs. In the near future the contributors to ConstitutionDAO will be able to do so privately, and with nearly 0 gas.

Because Aztec allows for these two new anonymizing activities — internal transactions and batched interactions with Layer 1 Ethereum— the privacy set is difficult for an observer to calculate.

That’s a very good thing.

Sleuthing and Deducing

Let’s put ourselves in the shoes of an adversary attempting to run de-anonymizing transaction graph analysis.

As an observer watching Ethereum activity, we might watch deposits to and from Aztec, and attempt to deduce what set of deposits a certain withdrawal might belong to.

This is what we mean by privacy or anonymity set — the group or set of users a forensic target could be. If the privacy set the target belongs to is large, then we can only guess with a small probability which addresses and transactions the target is associated with.

Once the privacy set you belong to approaches 1, the probability an observer knows who you are also approaches 1, and your privacy is no longer protected.

Let’s talk through an example.

Anonymity Sets 101

Pretend we were internet sleuths trying to de-anonymize other privacy protocols .️

If we saw someone withdraw 1 ETH, we’d know for certain that they’d deposited at least 1 ETH. Because there are no internal transfers, aggregation of multiple deposits into a larger withdrawal simply isn’t possible.

“So,” we’d puzzle, “all we need to figure out is how many people have ever deposited at least 1 ETH, and then the withdrawer must be one of those people!”

Good thing we have Dune Analytics to help us visualize how some of these privacy sets might work! You can see our privacy set dashboard here: https://dune.xyz/jaosef/Aztec-2.

The answer to the question of who the 1 ETH withdrawal could be in this case would be “everyone to the right of 1 ETH in this diagram,” which turns out to be 1,174 deposits.

The privacy set in a world without internal transfers.

Of course, the probability that a 1-ETH withdrawer came from the 1 ETH deposit set is much higher than the probability that she came from the >1 ETH deposit set, for a purely behavioral reason:

It’s annoying to break 5-, 10-, or 30-ETH deposits into smaller 1 ETH withdrawals. It’s much simpler to do one big monolithic withdrawal.

So as sophisticated sleuths, our investigative instincts would say that there is some non-zero but small probability that the withdrawer deposited an amount >1 ETH, with that probability diminishing for larger deposits:

This is an example of a simple probability distribution — and the “spikier” it is, the more certainty an adversary has about user behaviors.

In this case, based on observations of other protocols and comparable behaviors on Defi, a forensic analyst might think the probability of a 1 ETH withdrawal coming from a 5 ETH deposit is 5x lower than the probability of a 1 ETH withdrawal coming from a 1 ETH deposit.

Standing In or Standing Out

Let’s establish a rough heuristic guide to thinking about privacy sets:

In order to figure out how to blend in, figure out how to stand out, and then do the opposite.

The most obvious way for me to stand out in the case without internal transactions would be if I bridged a massive monolithic deposit and withdrew the same amount shortly afterward.

To make myself even more highly identifiable, I would use a unique quantity of a certain asset (e.g. depositing 69.696969 ETH to Aztec, then subsequently withdrawing 69.696969 ETH). To prevent de-anonymizing behavior, the zk.money front-end suggests round-number deposits and withdrawals — so you don’t stand out — and will soon also nudge users toward the largest anonymity sets.

As users what we want to do is introduce uncertainty into any forensic analysis. Keen observers should feel frustrated by our actions. They should say something like, “Dang, calculating the probability that these two addresses are affiliated is so complex and low-probability that it’s not meaningful for me to try to figure out which deposit is related to which withdrawal.”

I sum our conclusions in this extremely sophisticated 2x2 matrix of behaviors:

Very. Sophisticated.

So given what we know, how as a collective can we introduce more uncertainty into the adversary’s analysis?

  1. Increase the size of each deposit set, especially large deposits
  2. “Spread out” the probability that the withdrawal could have come from any deposit set!

Other protocols focus on #1. Let’s talk about what #2 adds.

Internal Transfers: The Inner Sanctum

There is a big caveat here that differentiates our current zk.money front-end — there is a possibility that your anonymity set includes deposits that are smaller than your withdrawal amount.

How? Because of internal transfers.

Say you withdraw 10 ETH. You could have deposited 10 ETH.

Or you could have deposited 5 ETH, used or coordinated offchain with 5 unassociated addresses to deposit and send you 1 ETH each internally, and then in the end withdrew 10 ETH. Suddenly you could be, well, pretty much anyone, so long as two things hold:

  • The amount of assets in the system is sufficient to support the hypothetical withdrawal scenario
  • The number of transactions in the intervening time exceeds the number needed to compose the hypothetical withdrawal scenario

So in this case, you could be some combination of internal transactions summing to 10E:

  • 10 internal 1E transfers
  • 100 internal 0.1E transfers
  • 1,000 internal 0.01E transfers
  • Some combination of the above

Of course, as the number of internal transfers needed to sum to a withdrawal amount increases, the less likely it actually happened — realistically, who’s going to coordinate 1,000 unaffiliated addresses to privately send them funds!

That’s why the internal economy of Aztec matters, and why Aztec Connect — a bridge allowing anyone to interact with defi contracts on Layer 1 — will help explode the anonymity set, making it highly improbable to associate any deposits with withdrawals.

Internal transfers muddy up anonymity set calculations, but only if there are a sufficient number of internal transfers and a large enough quantity of deposits in the system.

Aztec Connect: The Bridge to Infinity

Now let’s introduce the idea of Aztec Connect, an expansion of zk.money’s functionality to include batch interactions with any Layer 1 smart contract.

That means to begin with, any Layer 1 Defi functionality will be available to Aztec users.

Deposit $ETH on zk.money? On a competing protocol, you’d have to wait for the funds to be “seasoned” before withdrawal— essentially waiting for the privacy set to grow before withdrawing funds. That’s why for instance there are billions sitting in privacy protocols.

Using Aztec Connect, you can bridge funds back to Layer 1 and make shielded assets productive while you wait — meaning you might not want to ever withdraw!

With a simple conventional privacy protocol, you deposit funds and simply wait — for what, you ask? For the anonymity set to grow! Meanwhile, deposited funds are completely unproductive. Capital efficiency, schmapital efficiency.

Here are some arbitrary possible examples of using private assets while they are inside the system:

  • Staking ETH in Lido for stETH, depositing it in the stETH-ETH pool and getting double yield
  • Entering into an Element.fi fixed rate yield vault
  • Swapping ETH for OHM on OlympusDAO, staking for sOHM, and (3, 3)ing privately

This is just a teaser! We’ll cover Aztec Connect in depth later in this series, but for now I want to focus on the idea that investing capital for yield on Aztec will grow the value locked in the system.

Bridging back to Ethereum functionally has the same privacy-set-expanding benefits as having new users deposit fresh funds or having you deposit more funds, while being privacy-protected.

This spreads out the probability distribution:

And makes it less and less likely that you belong to any one given depositor set. Imagine depositing 0.1 ETH and (3, 3)ing on OlympusDAO until your OHM is worth 1 ETH! Now you’ve really thrown off the scent.

Purify Before Entering

Now, what Aztec doesn’t do is protect users on mainnet, and poor security hygiene on Ethereum can hurt user privacy.

But there’s some good news here — simply follow privacy best-practices.

Let’s start with one of the biggest no-no’s for any privacy preservation system: withdrawing to the same address.

Don’t do this.

Why is withdrawing to the same address “bad?” In addition to reducing your own anonymity, you’re basically screwing everyone else over. You’re reducing the anonymity set by removing yourself from it, saying, “I’m taking my ball back.”

Now there’s no way your deposit could actually be the source of anyone else’s withdrawal but your own!

Withdrawing to the same address you deposited is akin to saying, “These are the funds I brought! It’s special because my mommy gave it to me.” Okay Jimmy, that’s fine, but imagine if everyone did that. If everyone identified themselves and their funds, it would:

  1. defeat the purpose of using private transfers in the first place
  2. harm everyone else’s privacy
Jimmy always takes his ball back. Dang it, Jimmy.

Now consider the inverse: a large number of addresses deposit, and a large number (but not the same!) addresses withdraw. Now we’d have a very hard time associating one wallet with another.

Critically, any transaction graph analysis on Layer 1 may be able to associate those accounts and therefore collapse many addresses. Depositing to Aztec and withdrawing to an address already associated with the depository address is akin to withdrawing to the same address. That’s why withdrawals should only happen to untouched or otherwise unaffiliated wallets.

Hygiene takeaways:

  • Use common deposit and withdrawal amounts
  • Avoid making large deposits or large withdrawals (though large withdrawals are worse)
  • Don’t withdraw to the same address you deposited to

To Infinity and Beyond

We hope this helps you understand how and why Aztec Network builds upon the fundamental preservation mechanisms used by privacy protocols.

This stuff is meant to hurt your brain! The harder it is to deduce your set, the harder it is for a de-anonymizing foe. And if you are a researcher interested in de-anonymization, forensics, and transaction graph analysis, please reach out to us at hello@aztecprotocol.com.

Join the Aztec community

We’re also always on the lookout for talented engineers and applied cryptographers. If joining our mission to bring scalable privacy to Ethereum excites you — get in touch with us! hello@aztecprotocol.com.

And continue the conversation with us on Discord or Twitter.

Infinite Privacy: New Anonymity Paradigms with Aztec Network 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
4 Sep
xx min read

A New Brand for a New Era of Aztec

After eight years of solving impossible problems, the next renaissance is here. 

We’re at a major inflection point, with both our tech and our builder community going through growth spurts. The purpose of this rebrand is simple: to draw attention to our full-stack privacy-native network and to elevate the rich community of builders who are creating a thriving ecosystem around it. 

For eight years, we’ve been obsessed with solving impossible challenges. We invented new cryptography (Plonk), created an intuitive programming language (Noir), and built the first decentralized network on Ethereum where privacy is native rather than an afterthought. 

It wasn't easy. But now, we're finally bringing that powerful network to life. Testnet is live with thousands of active users and projects that were technically impossible before Aztec.

Our community evolution mirrors our technical progress. What started as an intentionally small, highly engaged group of cracked developers is now welcoming waves of developers eager to build applications that mainstream users actually want and need.

Behind the Brand: A New Mental Model

A brand is more than aesthetics—it's a mental model that makes Aztec's spirit tangible. 

Our Mission: Start a Renaissance

Renaissance means "rebirth"—and that's exactly what happens when developers gain access to privacy-first infrastructure. We're witnessing the emergence of entirely new application categories, business models, and user experiences.

The faces of this renaissance are the builders we serve: the entrepreneurs building privacy-preserving DeFi, the activists building identity systems that protect user privacy, the enterprise architects tokenizing real-world assets, and the game developers creating experiences with hidden information.

Values Driving the Network

This next renaissance isn't just about technology—it's about the ethos behind the build. These aren't just our values. They're the shared DNA of every builder pushing the boundaries of what's possible on Aztec.

Agency: It’s what everyone deserves, and very few truly have: the ability to choose and take action for ourselves. On the Aztec Network, agency is native

Genius: That rare cocktail of existential thirst, extraordinary brilliance, and mind-bending creation. It’s fire that fuels our great leaps forward. 

Integrity: It’s the respect and compassion we show each other. Our commitment to attacking the hardest problems first, and the excellence we demand of any solution. 

Obsession: That highly concentrated insanity, extreme doggedness, and insatiable devotion that makes us tick. We believe in a different future—and we can make it happen, together. 

Visualizing the Next Renaissance

Just as our technology bridges different eras of cryptographic innovation, our new visual identity draws from multiple periods of human creativity and technological advancement. 

The Wordmark: Permissionless Party 

Our new wordmark embodies the diversity of our community and the permissionless nature of our network. Each letter was custom-drawn to reflect different pivotal moments in human communication and technological progress.

  • The A channels the bold architecture of Renaissance calligraphy—when new printing technologies democratized knowledge. 
  • The Z strides confidently into the digital age with clean, screen-optimized serifs. 
  • The T reaches back to antiquity, imagined as carved stone that bridges ancient and modern. 
  • The E embraces the dot-matrix aesthetic of early computing—when machines first began talking to each other. 
  • And the C fuses Renaissance geometric principles with contemporary precision.

Together, these letters tell the story of human innovation: each era building on the last, each breakthrough enabling the next renaissance. And now, we're building the infrastructure for the one that's coming.

The Icon: Layers of the Next Renaissance

We evolved our original icon to reflect this new chapter while honoring our foundation. The layered diamond structure tells the story:

  • Innermost layer: Sensitive data at the core
  • Black privacy layer: The network's native protection
  • Open third layer: Our permissionless builder community
  • Outermost layer: Mainstream adoption and real-world transformation

The architecture echoes a central plaza—the Roman forum, the Greek agora, the English commons, the American town square—places where people gather, exchange ideas, build relationships, and shape culture. It's a fitting symbol for the infrastructure enabling the next leap in human coordination and creativity.

Imagery: Global Genius 

From the Mughal and Edo periods to the Flemish and Italian Renaissance, our brand imagery draws from different cultures and eras of extraordinary human flourishing—periods when science, commerce, culture and technology converged to create unprecedented leaps forward. These visuals reflect both the universal nature of the Renaissance and the global reach of our network. 

But we're not just celebrating the past —we're creating the future: the infrastructure for humanity's next great creative and technological awakening, powered by privacy-native blockchain technology.

You’re Invited 

Join us to ask questions, learn more and dive into the lore.

Join Our Discord Town Hall. September 4th at 8 AM PT, then every Thursday at 7 AM PT. Come hear directly from our team, ask questions, and connect with other builders who are shaping the future of privacy-first applications.

Take your stance on privacy. Visit the privacy glyph generator to create your custom profile pic and build this new world with us.

Stay Connected. Visit the new website and to stay up-to-date on all things Noir and Aztec, make sure you’re following along on X.

The next renaissance is what you build on Aztec—and we can't wait to see what you'll create.

Aztec Network
Aztec Network
22 Jul
xx min read

Introducing the Adversarial Testnet

Aztec’s Public Testnet launched in May 2025.

Since then, we’ve been obsessively working toward our ultimate goal: launching the first fully decentralized privacy-preserving layer-2 (L2) network on Ethereum. This effort has involved a team of over 70 people, including world-renowned cryptographers and builders, with extensive collaboration from the Aztec community.

To make something private is one thing, but to also make it decentralized is another. Privacy is only half of the story. Every component of the Aztec Network will be decentralized from day one because decentralization is the foundation that allows privacy to be enforced by code, not by trust. This includes sequencers, which order and validate transactions, provers, which create privacy-preserving cryptographic proofs, and settlement on Ethereum, which finalizes transactions on the secure Ethereum mainnet to ensure trust and immutability.

Strong progress is being made by the community toward full decentralization. The Aztec Network now includes nearly 1,000 sequencers in its validator set, with 15,000 nodes spread across more than 50 countries on six continents. With this globally distributed network in place, the Aztec Network is ready for users to stress test and challenge its resilience.

Introducing the Adversarial Testnet

We're now entering a new phase: the Adversarial Testnet. This stage will test the resilience of the Aztec Testnet and its decentralization mechanisms.

The Adversarial Testnet introduces two key features: slashing, which penalizes validators for malicious or negligent behavior in Proof-of-Stake (PoS) networks, and a fully decentralized governance mechanism for protocol upgrades.

This phase will also simulate network attacks to test its ability to recover independently, ensuring it could continue to operate even if the core team and servers disappeared (see more on Vitalik’s “walkaway test” here). It also opens the validator set to more people using ZKPassport, a private identity verification app, to verify their identity online.  

Slashing on the Aztec Network

The Aztec Network testnet is decentralized, run by a permissionless network of sequencers.

The slashing upgrade tests one of the most fundamental mechanisms for removing inactive or malicious sequencers from the validator set, an essential step toward strengthening decentralization.

Similar to Ethereum, on the Aztec Network, any inactive or malicious sequencers will be slashed and removed from the validator set. Sequencers will be able to slash any validator that makes no attestations for an entire epoch or proposes an invalid block.

Three slashes will result in being removed from the validator set. Sequencers may rejoin the validator set at any time after getting slashed; they just need to rejoin the queue.

Decentralized Governance

In addition to testing network resilience when validators go offline and evaluating the slashing mechanisms, the Adversarial Testnet will also assess the robustness of the network’s decentralized governance during protocol upgrades.

Adversarial Testnet introduces changes to Aztec Network’s governance system.

Sequencers now have an even more central role, as they are the sole actors permitted to deposit assets into the Governance contract.

After the upgrade is defined and the proposed contracts are deployed, sequencers will vote on and implement the upgrade independently, without any involvement from Aztec Labs and/or the Aztec Foundation.

Start Your Plan of Attack  

Starting today, you can join the Adversarial Testnet to help battle-test Aztec’s decentralization and security. Anyone can compete in six categories for a chance to win exclusive Aztec swag, be featured on the Aztec X account, and earn a DappNode. The six challenge categories include:

  • Homestaker Sentinel: Earn 1 Aztec Dappnode by maximizing attestation and proposal success rates and volumes, and actively participating in governance.
  • The Slash Priest: Awarded to the participant who most effectively detects and penalizes misbehaving validators or nodes, helping to maintain network security by identifying and “slashing” bad actors.
  • High Attester: Recognizes the participant with the highest accuracy and volume of valid attestations, ensuring reliable and secure consensus during the adversarial testnet.
  • Proposer Commander: Awarded to the participant who consistently creates the most successful and timely proposals, driving efficient consensus.
  • Meme Lord: Celebrates the creator of the most creative and viral meme that captures the spirit of the adversarial testnet.
  • Content Chronicler: Honors the participant who produces the most engaging and insightful content documenting the adversarial testnet experience.

Performance will be tracked using Dashtec, a community-built dashboard that pulls data from publicly available sources. Dashtec displays a weighted score of your validator performance, which may be used to evaluate challenges and award prizes.

The dashboard offers detailed insights into sequencer performance through a stunning UI, allowing users to see exactly who is in the current validator set and providing a block-by-block view of every action taken by sequencers.

To join the validator set and start tracking your performance, click here. Join us on Thursday, July 31, 2025, at 4 pm CET on Discord for a Town Hall to hear more about the challenges and prizes. Who knows, we might even drop some alpha.

To stay up-to-date on all things Noir and Aztec, make sure you’re following along on X.

Noir
Noir
26 Jun
xx min read

ZKPassport Case Study: A Look into Online Identity Verification

Preventing sybil attacks and malicious actors is one of the fundamental challenges of Web3 – it’s why we have proof-of-work and proof-of-stake networks. But Sybil attacks go a step further for many projects, with bots and advanced AI agents flooding Discord servers, sending thousands of transactions that clog networks, and botting your Typeforms. Determining who is a real human online and on-chain is becoming increasingly difficult, and the consequences of this are making it difficult for projects to interact with real users.

When the Aztec Testnet launched last month, we wrote about the challenges of running a proof-of-stake testnet in an environment where bots are everywhere. The Aztec Testnet is a decentralized network, and in order to give good actors a chance, a daily quota was implemented to limit the number of new sequencers that could join the validator set per day to start proposing blocks. Using this system, good actors who were already in the set could vote to kick out bad actors, with a daily limit of 5 new sequencers able to join the set each day. However, the daily quota quickly got bottlenecked, and it became nearly impossible for real humans who are operating nodes in good faith to join the Aztec Testnet.

In this case study, we break down Sybil attacks, explore different ways the ecosystem currently uses to prevent them, and dive into how we’re leveraging ZKPassport to prevent Sybil attacks on the Aztec Testnet.

Preventing Sybil Attacks

With the massive repercussions that stem from privacy leaks (see the recent Coinbase incident), any solution to prevent Sybil attacks and prove humanity must not compromise on user privacy and should be grounded in the principles of privacy by design and data minimization. Additionally, given that decentralization underpins the entire purpose of Web3 (and the Aztec Network), joining the network should remain permissionless.

Our goal was to find a solution that allows users to permissionlessly prove their humanity without compromising their privacy. If such a technology exists (spoiler alert: it does), we believe that this has the potential to solve one of the biggest problems faced by our industry: Sybil attacks. Some of the ways that projects currently try to prevent Sybil attacks or prove [humanity] include:

  • “Know Your Customer” (KYC): A process in which users upload a picture or scan of their government ID, which is checked and then retained (indefinitely) by the project, and any “bad actors” are rejected.
    • Pros: High likelihood they are human, although AI has begun to introduce a new set of challenges.
    • Cons: User data is retained and viewable by a centralized entity, which could lead to compromised data and privacy leaks, ultimately impacting the security of the individuals. Also, KYC processes in the age of AI means it is easy to fake a passport as only an image is used to verify and not any biometric data held on the passport itself. Existing KYC practices are outdated, not secure and prone to data leaks increasing personal security risk for the users.
  • On-chain activity and account linking (i.e, Gitcoin passport)
    • Pros: No personal identity data shared (name, location, etc.)
    • Cons: Onchain activity and social accounts are not Sybil-resistant.
  • Small payment to participate
    • Pros: Impractical/financially consequential for bots to join. Effective for centralized infra providers as it can cover the cost they incur from Sybil attacks.
    • Cons: Requires users to pay out of pocket to test the network, and doesn’t prevent bots from participating, and is ineffective for decentralized infra as it is difficult to spread incurred costs to all affected operators.
  • zkEmail
    • Pros: The user shares no private information.
    • Cons: Users cannot be blocked by jurisdiction, for example, it would be impossible to carry out sanctions checks, if required.
  • ZKPassport, a private identity verification app.
    • Pros: User verifies they possess a valid ID without sharing private information. No information is retained therefore no leaks of data can occur impacting the personal security of the user.
    • Cons: Users must have a valid passport or a compatible government ID, in each case, that is not expired.

Both zkEmail and ZKPassport are powered by Noir, the universal language of zk, and are great solutions for preventing Sybil attacks.

With zkEmail, users can do things like prove that they received a confirmation email from a centralized exchange showing that they successfully passed KYC, all without showing any of the email contents or personal information. While this offers a good solution for this use case, we also wanted the functionality of enabling the network to block certain jurisdictions (if needed), without the network knowing where the user is from. This also enables users to directly interface with the network rather than through a third-party email confirmation.

Given this context, ZKPassport was, and is, the perfect fit.

About ZKPassport

For the Aztec Testnet, we’ve integrated ZKPassport to enable node operators to prove they are human and participate in the network. This integration allows the network to dramatically increase the number of sequencers that can be added each day, which is a huge step forward in decentralizing the network with real operators.

ZKPassport allows users to share only the details about themselves that they choose by scanning a passport or government ID. This is achieved using zero-knowledge proofs (ZKPs) that are generated locally on the user’s phone. Implementing client-side zk-proofs in this way enables novel use-cases like age verification, where someone can prove their age without actually sharing how old they are (see the recent report on How to Enable Age Verification on the Internet Today Using Zero-Knowledge Proofs).

As of this week, the ZKPassport app is live and available to download on Google Play and the Apple App Store.

How ZKPassport works

Most countries today issue biometric passports or national IDs containing NFC chips (over 120 countries are currently supported by ZKPassport). These chips contain information on the full name, date of birth, nationality, and even digital photographs of the passport or ID holder. They can also contain biometric data such as fingerprints and iris scans.

By scanning the NFC chip located in their ID document with a smartphone, users generate proof based on a specific request from an app. For example, some apps might require only the user’s age or nationality. In the case of Aztec, no information is needed about the user other than that they do indeed hold a valid passport or ID.

Client-side proving

Once the user installs the ZKPassport app and scans their passport, the proof of identity is generated on the user's smartphone (client-side).

All the private data read from the NFC chip in the passport or ID is processed client-side and never leaves the smartphone (aka: only the user is aware of their data). Only this proof is sent to an app that has requested some information. The app can then verify the validity of the user’s age or nationality, all without actually seeing anything about the user other than what the user has authorized the app to see. In the case of age verification, the user may want to prove that they are over 18, so they’ll create a proof of this on their phone, and the requesting app is able to verify this information without knowing anything else about them.

For the Aztec Testnet, the network only needs to know that the user holds a valid passport, so no information is shared by the user other than “yes, I hold a valid passport or ID.”

Getting started with ZKPassport on Aztec Testnet

This is a nascent and evolving technology, and various phone models, operating systems, and countries are still being optimized for. To ensure this works seamlessly, we’ll be selecting the first cohort of people who have already been running active validators on a rolling basis to help test ZKPassport and provide early feedback.

If someone successfully verifies that they are a valid passport holder, they will be added to a queue to enter the validator set. Once they are in line, they are guaranteed entry. The queue will enable an estimated additional 10% of the current set to be allowed in each day. For example, if 800 sequencers are currently in the set, 80 new sequencers will be allowed to join that day.

This allows existing operators to maintain control of the network in the event that bad actors enter, while dramatically increasing the number of new validators added compared to the current number.

Humanizing Web3  

With ZKPassport now live, the Aztec Testnet is better equipped to distinguish real users from bots, without compromising on privacy or decentralization.

This integration is already enabling more verified human node operators to join the validator set, and the network is ready to welcome more. By leveraging ZKPs and client-side proving, ZKPassport ensures that humanity checks are both secure and permissionless, bringing us closer to a decentralized future that doesn’t rely on trust in centralized authorities.

This is exciting not just for Aztec but for the broader ecosystem. As the network continues to grow and develop, participation must remain open to anyone acting in good faith, regardless of geography or background, while keeping out bots and other malicious actors. ZKPassport makes this possible.

We’re excited to see the community expand, powered by real people helping to build a more private, inclusive, and human Web3.

Stay up-to-date on Noir and Aztec by following Noir and Aztec on X.

Noir
Noir
4 Jun
xx min read

StealthNote: The Decentralized, Private Glassdoor of Web3

Imagine an app that allows users to post private messages while proving they belong to an organization, without revealing their identity. Thanks to zero-knowledge proofs (ZKPs), it's now possible to protect the user’s identity through secure messaging, confidential voting, secured polling, and more. This development in privacy-preserving authentication creates powerful new ways for teams and individuals to communicate on the Internet while keeping aspects of their identity private.

Introducing Private Posting

Compared to Glassdoor, StealthNote is an app that allows users to post messages privately while proving they belong to a specific organization. Built with Noir, an open-source programming language for writing ZK programs, StealthNote utilizes ZKPs to prove ownership of a company email address, without revealing the particular email or other personal information.

Privately Sign In With Google

To prove the particular domain email ownership, the app asks users to sign in using Google. This utilizes Google’s ‘Sign in with Google’ OAuth authorization. OAuth is usually used by external applications for user authorization and returns verified users’ data, such as name, email, and the organization’s domain.

However, using ‘Sign in with Google’ in a traditional way reveals all of the information about the person’s identity to the app. Furthermore, for an app where you want to allow the public to verify the information about a user, all of this information would be made public to the world. That’s where StealthNote steps in, enabling part of the returned user data to stay private (e.g. name and email) and part of it to be publicly verifiable (e.g. company domain).

How StealthNote Works

Understanding JSON Web Tokens (JWTs)

When you "Sign in with Google" in a third-party app, Google returns some information about the user as a JSON Web Token (JWT) – a standard for sending information around the web.

JWTs are just formatted strings that contain a header (some info about the token), a payload (data about the user), and a signature to ensure the integrity and authenticity of the token:

Anyone can verify the authenticity of the above data by verifying that the JWT was signed by Google using their public key.

Adding Private Messages

In the case of StealthNote, we want to authorize the user and prove that they sent a particular message. To make this possible, custom information is added to the JWT token payload – a hashed message. With this additional field, the JWT becomes a digitally signed proof that a particular user sent that exact message.

Protecting the Sender’s Privacy

You can share the message and the JWT with someone and convince them that the message was sent by someone in the company. However, this would require sharing the whole JWT, which includes your name and email, exposing who the sender is. So, how does StealthNote protect this information?

They used a ZK-programming language, Noir, with the following goals in mind:

  • Verify the signature of the JWT using Google's public key
  • Extract the hashed message from the payload
  • Extract the email domain from the payload

The payload and the signature are kept private, meaning they stay on the user’s device and never need to be revealed, while the hashed message, the domain, and the JWT public key are public. The ZKP is generated in the browser, and no private data ever leaves the user's device.

Noir: What is Happening Under the Hood

By executing the program with Noir and generating a proof, the prover (the user who is posting a message) proves that they can generate a JWT signed by some particular public key, and it contains an email field in the payload with the given domain.

When the message is sent to the StealthNote server, the server verifies that the proof is valid as per the StealthNote circuit and validates that the public key in the proof is the same as Google's public key.

Once both checks pass, the server inserts the proof into the database, which then appears in the feed visible for other users. Other users can also verify the proof in the browser. The role of the server is to act as a data storage layer.

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