Worldcoin is launching by giving as many people as possible a share of a new currency.

Imagine a world where everyone around the globe, regardless of who they are, could participate in the growing space of digital economies and benefit from decentralized, collective ownership. What would it take to get there?

The first step is getting the same currency into the hands of as many people as possible. The more people there are that collectively hold and use the same currency, the more useful that currency becomes for each participant. While it’s not hard to see that widespread adoption is desirable, every currency faces a coordination problem on the way.

The same applies to cryptocurrencies and, so far, crypto as a technology has only reached about 3% of the world’s population[1]. While there have been amazing technological breakthroughs, there has not yet been a successful coordinated effort to achieve widespread, global adoption.

Worldcoin aims to overcome this coordination problem by aligning the incentives of all participants and allocating the majority of the currency to new users as a reward for joining the network.

Distinguishing new users in a way that can scale to the whole world is a hard problem. Our approach relies on a custom biometric device - we call it the Orb - that verifies the uniqueness of a person through iris recognition, while preserving their privacy through zero knowledge cryptography.

There were many technical challenges along the way. In the following sections, we describe our design decisions for different aspects of the problem including biometrics, hardware, crypto and economics. But to start, we want to offer a glimpse into what the global launch of Worldcoin might look like by providing the results from our field tests, which are already underway!

It is core to the mission of Worldcoin that the network is not run by a single entity, but instead by entrepreneurial individuals all around the world who apply to receive an Orb to run independent operations in their communities. We call these individuals *Orb Operators *and they have the autonomy to build their operations from the ground up, doing everything from running their own marketing campaigns to collaborating with local partners.

In order to test this model and technology, we have onboarded twenty-five Operators that run more than thirty devices in twelve countries across four continents (Africa, South America, Europe and Asia). In the coming months, the scale of these tests will increase as hundreds more devices and Orb Operators come online. After launch and an initial Orb production ramp-up phase, around four thousand devices will be distributed per month.

So far, the best performing Operators have been able to onboard around *one thousand users per Orb per week, *with our best performing Operator even signing up 2,198 users in one week with a single Orb. They have achieved these results despite using prototype devices (which are slower than the production model), facing frequent COVID disruptions, and not having the benefit of a public Worldcoin presence. In the four weeks before this post was published, the average weekly sign-up rate across all Operators was 764 per Orb and 1,069 per Operator.

To illustrate the success and potential of these Operators, we will dive deeper into the operations from the following five countries: Chile, Kenya, Indonesia, Sudan and France.

Currently, the longest-active Orb Operator in the world is based here. He has managed to sign up over eighteen- thousand users in a little over six months by running his operations like a business. He employs twenty people who work in shifts—at any given time, he has four people supporting his Orb operation. This allows him to keep his Orb active for eight hours a day, every day. His commitment to the project and its vision is astounding—while he normally operates out of Santiago, he aims to spread the project all throughout Chile, occasionally flying his team to smaller, more remote Chilean towns where he has had to secure special permission to operate and give away Worldcoin.

"I wake up every day knowing that we are educating hundreds of people about the future of tech. It is a real honor to be able to give them access to a new financial system run by the people, not by centralized organizations like governments and banks. We're building Singapore in Chile…unlocking opportunities for everyone."

One of the Orb Operators in Kenya typically partners with universities to run sign-up events. He has assembled a team of over thirty people so far. At optimal capacity, he runs events six days a week, all at different universities. At each event, he signs up between three and four hundred people. As word of what he was doing spread, universities around the country began to invite him to their campuses, with some invitations even sent directly from the presidents of the university. To keep up with this ever-increasing demand, he will often run two events concurrently in different locations, splitting up his four Orbs to efficiently sign up more people.

"Worldcoin has been an absolute eye-opener for me. It has been amazing to see cryptocurrency take off like this here in Kenya. Kenyans have been using mobile money for ages and see the possibility for Worldcoin to take things one step further: to help us become a cashless society. When it comes to people with no prior crypto knowledge, I love taking them through the history of cryptocurrency and explaining how Worldcoin will open up a whole new world for them. I do also like taking on the skeptics and the naysayers—I like the challenge!"

The best performing Orb Operator is currently based here, signing up over thirty thousand users in a little over four months. In his first week as an Operator, he set the highest single weekly sign-up total (at the time). Since then, he has partnered with one of the biggest food delivery companies in the country to sign up its drivers, rented out a storefront in a shopping mall to capitalize on high foot-traffic, and even been invited to a nearby village to sign up all those who live there to Worldcoin. His time signing up the village was so successful that it resulted in eight other villages asking him to do the same.

"Of course, I was highly motivated by the Worldcoin sign-up incentive scheme: I want to provide a better life for my family. But along the way, seeing people who don't have access to crypto - who don't even know this technology exists - makes me grateful to be a part of this project."

The four Orb Operators in Sudan secure partnerships with coffee stores in Khartoum and strike deals with various Sudanese influencers to market Worldcoin. Each Operator runs a large team that, out of pure passion, works up to fourteen hours a day. On a busy day, people will often wait up to three hours to sign up. To support this demand, the Operators recently booked out the largest and most well-known venue in Khartoum, which has even hosted presidential speeches, to run an event at which they aim to sign up over a thousand people in a single day.

"I get to meet new people every day and give them something that may benefit them in the future. We have suffered a lot financially here in Sudan, so getting a chance to add value to my community is really fulfilling."

This Operator has set up a team of 15 people, mostly local students, and ensures that they are well trained so that they can speak intelligently about Worldcoin and cryptocurrency in general. He has set up a digital platform for his employees so that they can easily book a time slot to use the Orb. He has also created a very detailed incentive system for his employees that rewards them for both additional employee referrals and performance in the field. He and his team operate around Paris’s famed Châtelet metro station, the biggest underground train station in the world.

"There are two main reasons I believe the project will succeed: accessibility and equality. Worldcoin offers what has been missing in the crypto-sphere for a while now: equal opportunity to enter the world of DeFi for free. Worldcoin’s approach is simple and will give access to millions, if not billions of people."

We decided to perform a thought experiment using the numbers we have seen in the field to make these results more tangible and help visualize what could happen with increased Orb production. The figure below demonstrates how cumulative sign-ups over time could increase significantly as more Orbs come online. Although we anticipate there will be all kinds of saturation effects and other complications, we believe that there is a path for this model to onboard billions of users.

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**Fig. 1
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Thought Experiment
Schematic visualization of how Orb performance (sign-ups per week) could increase with the planned production schedule. The lower end illustrates an average of 350 sign-ups per week, while the maximum is at 1400. The dotted line represents 700 sign-ups per week, which is approximately equal to the average performance observed in the field in early October 2021. This is by no means a prediction but rather an oversimplified model to visualize some different scaling scenarios.

**Testing Sign-ups
**Testing data since May, 2021, showing key operator milestones and cumulative field test sign-ups. So far, over 130,000 users have signed up to Worldcoin, with 60,000 of these sign-ups coming in just the last four weeks. All of this has been achieved with less than 30 prototype Orbs in the field.

We are thrilled by these results—they show that our strategy for getting crypto into the hands of as many people as possible just might work. Of course, these are still early days and achieving widespread adoption is really just the beginning, but these results are certainly promising. 

In the following sections, we want to present the technical challenges that we needed to solve in order to get to this point.

The launch of Worldcoin requires a robust and scalable way to determine whether someone is unique (in a sense of new) and actually human (not a bot). So-called Proof-of-Personhood protocols[2, 3] try to solve this problem by allowing people to prove they are “unique humans”[4]. This “unique-human proof” would unlock many meaningful applications[5], but none of the existing approaches have yet reached a global scale.

Could one just use existing government IDs for Proof-of-Personhood?  Aside from requiring a central authority, they are a poor choice for reasons related to privacy and practicality. Not to mention that many people simply don’t have government IDs[6]. Phone numbers, emails, or social accounts have similar issues, and also fail to ensure uniqueness because they can be acquired multiple times.

The all-too-familiar CAPTCHA[7] was one of the first approaches towards a Proof-of-Personhood for the internet. It is a test designed to be difficult for bots, but easy for humans.  While it does well in verifying humanness, CAPTCHA fails to verify uniqueness: as a human, you can pass as many tests as you want. This could be addressed by requiring everybody to solve a CAPTCHA challenge** at the same time**[8], but that would be very difficult to coordinate on a large scale. 

Many other approaches to Proof-of-Personhood[9, 10, 11] have been deployed. Some of these use social verification to ensure accounts are owned by unique humans. This often requires that existing users meet (physically or virtually) new users and deposit some form of financial stake that can be taken away in case of fraud. Social verification systems may lead to a robust Proof-of-Personhood, but they also face difficult scaling challenges.

Biometric approaches (e.g., Aadhaar in India) are promising as they are both accessible and enable accurately verifying uniqueness. The key challenges for biometric approaches are related to privacy, fraud detection, and scalability. We believe that recent advances in technology offer a way to solve these issues.

Worldcoin leverages biometrics, cryptography, and incentives to create a scalable, privacy-preserving solution to the “unique-human problem”. The following sections describe how the system works and details how we plan to deploy it globally.

At their core, biometric systems usually consist of:

1. A device that acquires biometric information (e.g., fingerprints) and converts them to a compressed representation (an “embedding”); and

2. A database that stores these embeddings for later retrieval and comparison.

Embeddings are designed so that one can calculate a distance (in the sense of similarity) between two embeddings. If this distance is above a certain threshold, the two embeddings are assumed to belong to different people.

One typically distinguishes between two modes of operation for biometric systems: verification and identification.

Verification is the most familiar use case of biometrics. For example, access to a building may require a keycard and a fingerprint scan. Here, fingerprint verification helps ensure that a stolen keycard cannot be used to enter the building. Behind the scenes, the keycard is linked to an embedding in the database, which is compared to the one of the scanned finger.

FaceID works in the same way. But instead of the user providing a keycard, the phone already knows which face(s) it needs to compare to as the database of users consists of only a single user.

In the case of identification, there is no keycard available to help: the biometric system has to determine a user’s identity from the biometric scan alone. A common use-case for biometric identification is in forensics where, for example, a fingerprint or DNA sample is compared with every entry in a database to identify a suspect.

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Fig. 2

Schematic explanation of the difference between biometric verification and identification:

While verification only requires comparison to a single piece of data, identification requires searching an entire database for a match.

A biometric system can be used as the foundation for Proof-of-Personhood by ensuring each person can only register once. Similar to biometric identification, the system needs to compare each user’s embedding to every other entry in the database. If none match, the user’s registration is successful and their embedding is added to the database. If there is a match, the user has likely registered before and is therefore rejected. 

However, there is a significant challenge with this approach: the identification problem becomes increasingly difficult with a growing database. Issues with search complexity and performance come into play, but more importantly, the system starts making more errors while trying to match users. These errors are largely governed by the “false match rate” (FMR). The FMR measures the likelihood that two biometric scans are incorrectly considered the same. At the scale of billions of users, the FMR must be extremely small to avoid frequently rejecting legitimate new users.

The key to being able to scale such a system to onboard billions of people is capturing an information-rich biometric source at a high level of fidelity. The more information the source contains, the lower the probability of false matches.

The likelihood of incorrectly rejecting legitimate new users is related to the Birthday Problem[12]: in a group of n randomly chosen people, how large should n be for two people to share the same birthday with a probability greater than 50%. The answer, 23, is counterintuitively low and demonstrates how likely random collisions are. In our specific implementation it turns out that the FMR has to decrease quadratically with the total number of expected users. To keep false rejections low at the scale of one billion users, the FMR needs to be below 1e-12 (that’s one in a trillion).

We evaluated many different technologies and believe that iris recognition is the best-suited for our biometric approach to Proof-of-Personhood. Compared to other biometric methods, like face recognition, fingerprints and DNA sequencing, iris recognition stands out by simultaneously satisfying the following three criteria: 

1. Uniqueness: The iris theoretically contains enough information to distinguish nearly all humans uniquely.

2. Fraud-resistance: The iris is difficult to physically modify and the biometric capture can be made hard to spoof.

3. Practicality: The required imaging technology already exists, and for the user, presenting their iris can be a fast and simple process.

On a global scale, a biometric uniqueness check must confidently distinguish each person from every other person. The information density of the iris is high enough to allow this, and no two irises are alike (even for identical twins). It also turns out that it is possible to capture most of this information with high-resolution imaging of the iris. 

The same is not true for today’s face recognition technology: at the scale of billions of people, there is simply not enough information in, for example, a selfie to reliably tell people apart. Even advanced algorithms such as neural networks can’t help. 

The information of the iris pattern is distilled into an embedding, in our case the so-called IrisHash, which is derived from a one-way function with the iris image as the input. This code is stored in a database and is the only data used for checking uniqueness. Under this approach, the original image of the iris does not need to be stored anywhere.

We describe this in more detail in our post on privacy.

We target an FMR of 1e-6 per eye (thus 1e-12 for both eyes combined). At a scale of one billion people, we estimate that around 0.05% of users will be accidentally rejected. We also target a false non-match rate (FNMR) of 1/7000, such that (on average) a user has to try signing up seven thousand times before they can register twice.

Using the iris also enables a strong degree of fraud-resistance. In the context of our biometric uniqueness check, this means we need to reliably detect if someone attempts to spoof the biometric capture (e.g., using animals or special contact lenses). Since cheating a uniqueness check only requires looking different than any existing user, the fraud resistance property of the iris is critical. The iris is inherently hard to modify and enables better ways to verify liveness compared to other common biometrics like faces and fingerprints.

Finally, any scalable uniqueness check must be fast and simple. From the user’s perspective, presenting an iris is as easy as posing for a photo. In fact, the practicality of iris recognition has already been proven at scale. One notable example is the border control system for the United Arab Emirates, which leverages iris recognition[13]. Some other biometric approaches, like DNA sequencing, may not provide the same degree of simplicity for the user, and can feel invasive.

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Fig. 3

Schematic representation illustrating the importance of high-quality imaging for decreasing error:

Here we sample pairwise comparisons by calculating the distances between embeddings. Since we  do this on an evaluation dataset, we know the ground truth and can plot the two distributions: the match distribution for pairs of the same identity (blue) and non-match distribution for pairs of different identity (red). 

In a perfect system, the match-distribution would be a very narrow peak at zero. However multiple sources of error widen the distribution leading to more overlap with the non-match distribution and therefore increasing False Match and False Non-Match rates. High quality image acquisition narrows the match-distribution significantly and therefore minimizes errors. The width of the non-match distribution is determined by the amount of information that is extracted by the biometric algorithm: the more information is encoded in the embeddings the narrower the distribution.

Using iris recognition for a scalable Proof-of-Personhood requires an iris scanner that’s secure, high-resolution, and easy-to-use. We searched for existing devices that meet these requirements at a global scale, but found none. For this reason, Worldcoin developed the Orb.

Fig. 4

A photo (not a render) of the Orb production model. The device has a diameter of 20 centimeters and weighs around 2.5 kg (5 lbs).  The surface of the Orb is mirror chrome. An LED ring guides the user through the sign-up process. Behind the black surfaces, the Orb has an eye-imaging system, infrared LEDs for illumination, and a fraud-detection system. An exchangeable battery is accessible from below to enable continuous mobile operation.

The primary function of the Orb is to capture detailed images of a person’s eyes, and convert them to an IrisHash. From the outside, the UX is simple: users simply look into the camera (which is behind the black surfaces) and press a button. On the inside of the Orb, a custom optical system automatically finds the user's eyes and brings them into focus. The Orb then captures high-resolution images of both irises at multiple infrared wavelengths, then uses them to locally compute the user’s IrisHashes.

To work at scale, the Orb must reliably capture high-quality iris images across a variety of lighting conditions and distances from the user. This adaptability is achieved using a combination of custom optics hardware and machine learning. To quickly find the user’s eyes, the Orb uses a movable mirror that is guided by a neural network. Once the eye is in-frame, another neural network controls a custom liquid lens to focus on the detailed patterns in the user’s iris. All of this happens while the Orb’s infrared LEDs are adaptively illuminating the eye, ensuring consistent images across lighting environments.

Together, these systems enable the Orb to capture irises with significantly higher quality: up to two orders of magnitude higher resolution compared to the industry standard[14, 15]. At this level of detail, the unique patterns in the iris can be used to reliably distinguish between billions of people.

To reduce complexity, the majority of commercial iris scanners today use goggles to align the subject precisely with the camera and block external light.

Fig. 5

On a high level, the Orb performs the following tasks:

Scan QR code
The device scans a QR code on the user's phone such that she can later prove that she has signed up.

**Capture Images
**After scanning the QR code the device captures multiple high-resolution multispectral images of the user.

**Generate IrisHash
**Based on the captured images, the device calculates a unique IrisHash through a one-way function.

Verify integrity
A custom set of security sensors ensures that the sign-up is legitimate.

Security is core to the Orb's design. After all, Worldcoin requires trusting that the IrisHashes are legitimately produced by an Orb. The Orb’s security system ensures the authenticity of each IrisHash by robustly detecting a wide range of fraudulent behaviors. Broadly, we can classify such behavior as either spoofing or tampering.

Unlike iris scanners used at border checkpoints, the Orb is deployed to unsecured environments and used by independent Operators. This is made possible by the Orb’s secure design, and is a key requirement for scaling Worldcoin.

Spoofing attacks involve presenting the Orb with modified, fake, or non-human irises. For example, an attacker might show the Orb a photo of an iris or an animal iris, hoping to generate a unique IrisHash. To defend against attacks like this, we’ve equipped the Orb with a suite of multi-spectral sensors and custom fraud-detection algorithms. This advanced anti-spoofing system complements the iris imaging system, and operates locally on each device.

The Orb is also resilient to various forms of tampering, including attempts to modify its software, extract its cryptographic secrets, or disable its anti-spoofing system. This resilience is critical, since any of these intrusions might allow a hacker to generate fraudulent IrisHashes. The Orb’s embedded systems reliably detect advanced attacks of this kind, and prevent corresponding fraud.

No biometric system is impenetrable to spoofing or tampering, given enough resources. That said, we’re confident that the Orb’s state-of-the-art security systems will prevent fraud deemed profitable for a would-be attacker.

To further increase the difficulty of an attack, Orbs will be remotely monitored and compared to other Orbs. Such monitoring is based on non-biometric metadata from the Orb, including battery level, temperature, and network strength. Anomalies will be flagged and lead to Orbs being deactivated. This anomaly detection happens in a controlled environment in the cloud and therefore comes with higher security guarantees than device-level spoof and tamper detection.

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Fig. 6

Left: Incentive model built around the Orb. Operators receive a  reward for each sign-up, incentivizing them to maximize their sign-up rate.

Right: Orbs are a scarce resource and must be allocated to the most efficient Operators. To this end, short-term contracts for operating the Orbs are allocated to Operators via a bidding process.

While the Orbs are important to solve the unique-human problem, it must also be ensured that those Orbs are used in the most effective way. Therefore, each Orb will be handled by the Orb Operator whose task it is to explain Worldcoin to new users and to operate the Orb to help them sign up. Operators receive a small reward(in Worldcoin) for each sign-up, which incentivizes them to maximize their *sign-up rate *(i.e., the number of sign-ups per week). Combined with the proof-of-personhood, this makes Worldcoin the first cryptocurrency to directly encode, into its trustless protocol, the economic incentives for users to join the network: giving every new user a share of its currency.

Cryptocurrencies like bitcoin typically pay miners for block production via issuance of its own currency. However, since Worldcoin and the Layer 2 are secured by the underlying Ethereum network, there is no need to incentivize miners or validators via the currency. Instead, the issuance of the currency can be directly allocated to users.

Still, one challenge is to find Operators that can actually achieve a high sign-up rate. This can be done at scale through a *bidding process *that allocates Orbs to the most efficient Operators. Concretely, Operators bid for the right to operate one or multiple Orbs for a defined period of time. Operators who sign up more users than others will achieve a higher monthly revenue, so they can be expected to submit higher bids, making them more likely to win the bidding process. Additional incentive structures are in place for promoting not only raw number of sign-ups, but also high-engagement of users and disincentivizing fraud. We will share more details about those mechanisms in the future.

The described incentive mechanism is core to Worldcoin. Out of the fixed supply of 10 billion tokens, twenty percent are used to fund Orb production and initial protocol development. But the rest and vast majority of the tokens will be given to users and Operators that are helping to launch Worldcoin through the protocol. Finally, to incentivize early adoption of the currency, the number of tokens that users and Operators receive per sign-up will decay over time.

With the Orb, Worldcoin aims to onboard the first billion users into the world of cryptocurrency. We believe Worldcoin can reach this unprecedented scale by leveraging recent innovations in blockchain scalability and embracing compatibility with the existing crypto ecosystem. This section details our approach, including the mechanisms for ensuring user privacy.

We expect most Worldcoin users to receive their account via the Orb, but this is not required. Anybody can create a Worldcoin account using any digital wallet built with our open-source SDK (see Wallet & SDK below). However, accounts created without an Orb do not receive free tokens at launch.

Worldcoin’s scalability is provided by an optimistic rollup[16, 17] on top of Ethereum. This "layer 2" scaling solution ensures transactions will remain cheap, fast, and reliable as the Worldcoin network grows. Importantly, this solution maintains the open and permissionless nature of Ethereum: anybody can create accounts, submit transactions, and participate in validation. The optimistic rollup is built using the open-source Hubble project[18], extended with a high-performance node that will be open-sourced in the coming weeks.

Worldcoin aims for broad compatibility. The underlying token is based on Ethereum’s popular ERC-20 standard, enabling compatibility with many existing tools and services. In addition, our open-source SDKs (see Wallet & SDK) will make it very easy for developers to interact with the currency and the Layer 2. 

Users are free to withdraw their funds to Ethereum mainnet or migrate through bridges to any Layer 2 on Ethereum (e.g., Optimism, Arbitrum, and many others) or even separate and aspiring ecosystems, such as Solana or Polkadot.

Fig. 7

Protocol architecture

1. The user generates a Semaphore public key and presents it hashed as a QR code to the Orb.

2. The Orb performs the iris scan and sends the created IrisHashalong with the Semaphore key to the current sign-up sequencer.

3. The sequencer validates the sign-up by checking the IrisHash for uniqueness in the database. If successful, it registers the Semaphore key on-chain.

4. The app locally generates a Hubble public key and submits it with a Semaphore zero knowledge proof to claim the reward.

5. The proof is verified and the reward is sent directly to the user’s public key in the Hubble rollup.

Worldcoin inherits Ethereum's privacy model: accounts are pseudonymous and transactions are public. Crucially, Worldcoin accounts are never associated with any biometric data from the Orb. Zero-knowledge proofs (ZKPs) are the enabling technology behind this privacy-preserving biometric approach. We use the open-source Semaphore[19] zero-knowledge proof system to transfer the uniqueness of IrisHashes to the uniqueness of user accounts, without linking them.

A zero-knowledge proof (ZKP) ensures a given statement is true, without disclosing any information about the statement (except that it's true). For Worldcoin, the "statement" is "this account is associated with a unique IrisHash". And that statement is either true or false. The corresponding IrisHash is never revealed. Recent advances in zero-knowledge proofs have made their use on smartphones practical.

Phase 1: Sign-up and uniqueness check

1. The user generates a Semaphore keypair on her phone

2. The user presents the hashed public key (via QR code) to the Orb.

3. The Orb scans the user’s irises and locally computes the user’s IrisHashes.

4. The Orb sends a signed message containing the hashed public key and the IrisHashes to the sign-up sequencer node.

5. The sequencer node verifies the Orb’s signature, then checks if the IrisHashes do not match any already in the database. If the uniqueness check passes, the IrisHashes and the public key are saved.

Phase 2: Claiming the reward

1. The user’s app locally generates a wallet address.

2. The app uses Semaphore to prove that it owns the private counterpart to one public key registered in phase 1. Because it’s a zero-knowledge proof, it does not reveal which public key.

3. The proof is sent again to the sequencer, which verifies it and initiates the deposit of tokens to the provided wallet address.

4. A so-called *nullifier *is sent along with the proof and ensures the user cannot claim the reward twice.

Those two steps - decoupled by the zero-knowledge proof - enable a biometric-based Proof-of-Personhood without linking user accounts to biometric data. A more visual explanation of account privacy can be found in our dedicated privacy blog post.

The "sequencer node" can operate trustlessly via optimistic verification in a smart contract. It also exists for optimization reasons. Users actually don’t submit proofs directly to a smart contract, but the sequencer first verifies and then batches them together with many other proofs.

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Fig. 8

**Privacy
**The whole process consists of two independent actions: Sign-up and Claim. The Orb sign-up links the IrisHash to the SemaphoreHash. This SemaphoreHash is never used publicly for anything that could be directly tied to the user. It is only used to prove membership within a set of registered users. However, this can be done through a zero knowledge proof that does not leak any other information about the user. This makes it possible for the verifier to check whether the user has signed up without knowing any identifiable information from the sign-up.

Worldcoin is designed to be the first widely-adopted cryptocurrency. Making this a reality means going further than having an inclusive launch: Worldcoin must be useful and understandable to people with no prior experience using digital money. In addition, users must be confident in the privacy and security of their accounts. Because of this, we are developing a mobile wallet application.

The wallet allows users to learn about Worldcoin and other cryptocurrencies, find Orb Operators, claim their share, view their balance, send global peer-to-peer payments, and use their Worldcoin throughout the Ethereum ecosystem. No central authority mediates transactions; users always have full control and ownership of their Worldcoin (i.e., the wallet is “non-custodial”), which they can back up if they choose.

Fig. 9

**Wallet
*****Illustrative wireframe, not actual product images.
*For most people, Worldcoin will be their first contact with a cryptocurrency, and for some, their first with any kind of digital money. The applications of crypto are far bigger, but as the initial use-case for first-time users, the wallet will enable instant peer-to-peer payments to anyone in the world.

In addition to the wallet, we are developing a collection of open-source Software Development Kit (SDKs) to help developers build products around Worldcoin—things like alternative clients, tools for niche use-cases, digital tipping, in-store payments, and professional interfaces. These SDKs, coupled with pre-existing decentralized financial protocols, will allow anyone to serve the needs of local, regional, and global markets.

Most excitingly, these SDKs will eventually include zero-knowledge Proof-of-Personhood for third-party applications, maintaining user privacy as described in the Account Privacy section. While we built the Orb to help make Worldcoin a reality, we know this primitive can unlock much more. That’s why we want to give everyone the ability to reuse their already issued proofs to access other projects.

We believe the wallet and SDKs will help make Worldcoin — and the larger crypto ecosystem — more accessible and useful. We’re excited to share more details about these tools over the coming months.

There are many ways in which Worldcoin can have substantial positive effects on our society. Still, we strongly believe that how we accomplish this project is just as important as what we achieve. Our design approach is based as much on our own deeply-held values as on technical reasoning. We are choosing to prioritize user privacy, data security, openness, and broad accessibility, even when it means tackling some of today's toughest engineering and operational challenges.

For example, building on Ethereum at this scale is more challenging than operating a custom, centralized blockchain, at least in the short-term. The same applies to the privacy approach using zero-knowledge proofs, which is on the edge of current research. But we think this is the right way to launch Worldcoin, and the effort will pay off in the long run for all of us.

If successful, Worldcoin will, within the first year, onboard hundreds of millions of new people who didn’t have access to this technology. This will hopefully result in many developers integrating Worldcoin into new and existing products. We believe the internet has entered a new era: web3, where finally economic value and ownership are natively integrated into the web. It is hard to imagine what new products this coming era will bring us. Certainly, it will involve wider adoption of novel technologies and models of collaboration, like DAOs, NFTs, and decentralized exchanges.

There’s still a lot of work to do to enable and support a rapidly sprawling ecosystem of developers, entrepreneurs, and community builders. We are in the early stages of designing Worldcoin’s long-term governance strategy, grant programs, and partnerships roadmap. We are committed to following credible neutrality[20] as a key guiding principle in setting up these mechanisms. 

There are still many challenges left, and we will continue our research on many of them, such as blockchain scalability, digital identity, and pseudonymous economies.

Join us and let’s build together!

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Worldcoin is launching by giving as many people as possible a share of a new currency.

Imagine a world where everyone around the globe, regardless of who they are, could participate in the growing space of digital economies and benefit from decentralized, collective ownership. What would it take to get there?

The first step is getting the same currency into the hands of as many people as possible. The more people there are that collectively hold and use the same currency, the more useful that currency becomes for each participant. While it’s not hard to see that widespread adoption is desirable, every currency faces a coordination problem on the way.

The same applies to cryptocurrencies and, so far, crypto as a technology has only reached about 3% of the world’s population[1]. While there have been amazing technological breakthroughs, there has not yet been a successful coordinated effort to achieve widespread, global adoption.

Worldcoin aims to overcome this coordination problem by aligning the incentives of all participants and allocating the majority of the currency to new users as a reward for joining the network.

Distinguishing new users in a way that can scale to the whole world is a hard problem. Our approach relies on a custom biometric device - we call it the Orb - that verifies the uniqueness of a person through iris recognition, while preserving their privacy through zero knowledge cryptography.

There were many technical challenges along the way. In the following sections, we describe our design decisions for different aspects of the problem including biometrics, hardware, crypto and economics. But to start, we want to offer a glimpse into what the global launch of Worldcoin might look like by providing the results from our field tests, which are already underway!

It is core to the mission of Worldcoin that the network is not run by a single entity, but instead by entrepreneurial individuals all around the world who apply to receive an Orb to run independent operations in their communities. We call these individuals *Orb Operators *and they have the autonomy to build their operations from the ground up, doing everything from running their own marketing campaigns to collaborating with local partners.

In order to test this model and technology, we have onboarded twenty-five Operators that run more than thirty devices in twelve countries across four continents (Africa, South America, Europe and Asia). In the coming months, the scale of these tests will increase as hundreds more devices and Orb Operators come online. After launch and an initial Orb production ramp-up phase, around four thousand devices will be distributed per month.

So far, the best performing Operators have been able to onboard around *one thousand users per Orb per week, *with our best performing Operator even signing up 2,198 users in one week with a single Orb. They have achieved these results despite using prototype devices (which are slower than the production model), facing frequent COVID disruptions, and not having the benefit of a public Worldcoin presence. In the four weeks before this post was published, the average weekly sign-up rate across all Operators was 764 per Orb and 1,069 per Operator.

To illustrate the success and potential of these Operators, we will dive deeper into the operations from the following five countries: Chile, Kenya, Indonesia, Sudan and France.

Currently, the longest-active Orb Operator in the world is based here. He has managed to sign up over eighteen- thousand users in a little over six months by running his operations like a business. He employs twenty people who work in shifts—at any given time, he has four people supporting his Orb operation. This allows him to keep his Orb active for eight hours a day, every day. His commitment to the project and its vision is astounding—while he normally operates out of Santiago, he aims to spread the project all throughout Chile, occasionally flying his team to smaller, more remote Chilean towns where he has had to secure special permission to operate and give away Worldcoin.

"I wake up every day knowing that we are educating hundreds of people about the future of tech. It is a real honor to be able to give them access to a new financial system run by the people, not by centralized organizations like governments and banks. We're building Singapore in Chile…unlocking opportunities for everyone."

One of the Orb Operators in Kenya typically partners with universities to run sign-up events. He has assembled a team of over thirty people so far. At optimal capacity, he runs events six days a week, all at different universities. At each event, he signs up between three and four hundred people. As word of what he was doing spread, universities around the country began to invite him to their campuses, with some invitations even sent directly from the presidents of the university. To keep up with this ever-increasing demand, he will often run two events concurrently in different locations, splitting up his four Orbs to efficiently sign up more people.

"Worldcoin has been an absolute eye-opener for me. It has been amazing to see cryptocurrency take off like this here in Kenya. Kenyans have been using mobile money for ages and see the possibility for Worldcoin to take things one step further: to help us become a cashless society. When it comes to people with no prior crypto knowledge, I love taking them through the history of cryptocurrency and explaining how Worldcoin will open up a whole new world for them. I do also like taking on the skeptics and the naysayers—I like the challenge!"

The best performing Orb Operator is currently based here, signing up over thirty thousand users in a little over four months. In his first week as an Operator, he set the highest single weekly sign-up total (at the time). Since then, he has partnered with one of the biggest food delivery companies in the country to sign up its drivers, rented out a storefront in a shopping mall to capitalize on high foot-traffic, and even been invited to a nearby village to sign up all those who live there to Worldcoin. His time signing up the village was so successful that it resulted in eight other villages asking him to do the same.

"Of course, I was highly motivated by the Worldcoin sign-up incentive scheme: I want to provide a better life for my family. But along the way, seeing people who don't have access to crypto - who don't even know this technology exists - makes me grateful to be a part of this project."

The four Orb Operators in Sudan secure partnerships with coffee stores in Khartoum and strike deals with various Sudanese influencers to market Worldcoin. Each Operator runs a large team that, out of pure passion, works up to fourteen hours a day. On a busy day, people will often wait up to three hours to sign up. To support this demand, the Operators recently booked out the largest and most well-known venue in Khartoum, which has even hosted presidential speeches, to run an event at which they aim to sign up over a thousand people in a single day.

"I get to meet new people every day and give them something that may benefit them in the future. We have suffered a lot financially here in Sudan, so getting a chance to add value to my community is really fulfilling."

This Operator has set up a team of 15 people, mostly local students, and ensures that they are well trained so that they can speak intelligently about Worldcoin and cryptocurrency in general. He has set up a digital platform for his employees so that they can easily book a time slot to use the Orb. He has also created a very detailed incentive system for his employees that rewards them for both additional employee referrals and performance in the field. He and his team operate around Paris’s famed Châtelet metro station, the biggest underground train station in the world.

"There are two main reasons I believe the project will succeed: accessibility and equality. Worldcoin offers what has been missing in the crypto-sphere for a while now: equal opportunity to enter the world of DeFi for free. Worldcoin’s approach is simple and will give access to millions, if not billions of people."

We decided to perform a thought experiment using the numbers we have seen in the field to make these results more tangible and help visualize what could happen with increased Orb production. The figure below demonstrates how cumulative sign-ups over time could increase significantly as more Orbs come online. Although we anticipate there will be all kinds of saturation effects and other complications, we believe that there is a path for this model to onboard billions of users.

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**Fig. 1
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Thought Experiment
Schematic visualization of how Orb performance (sign-ups per week) could increase with the planned production schedule. The lower end illustrates an average of 350 sign-ups per week, while the maximum is at 1400. The dotted line represents 700 sign-ups per week, which is approximately equal to the average performance observed in the field in early October 2021. This is by no means a prediction but rather an oversimplified model to visualize some different scaling scenarios.

**Testing Sign-ups
**Testing data since May, 2021, showing key operator milestones and cumulative field test sign-ups. So far, over 130,000 users have signed up to Worldcoin, with 60,000 of these sign-ups coming in just the last four weeks. All of this has been achieved with less than 30 prototype Orbs in the field.

We are thrilled by these results—they show that our strategy for getting crypto into the hands of as many people as possible just might work. Of course, these are still early days and achieving widespread adoption is really just the beginning, but these results are certainly promising. 

In the following sections, we want to present the technical challenges that we needed to solve in order to get to this point.

The launch of Worldcoin requires a robust and scalable way to determine whether someone is unique (in a sense of new) and actually human (not a bot). So-called Proof-of-Personhood protocols[2, 3] try to solve this problem by allowing people to prove they are “unique humans”[4]. This “unique-human proof” would unlock many meaningful applications[5], but none of the existing approaches have yet reached a global scale.

Could one just use existing government IDs for Proof-of-Personhood?  Aside from requiring a central authority, they are a poor choice for reasons related to privacy and practicality. Not to mention that many people simply don’t have government IDs[6]. Phone numbers, emails, or social accounts have similar issues, and also fail to ensure uniqueness because they can be acquired multiple times.

The all-too-familiar CAPTCHA[7] was one of the first approaches towards a Proof-of-Personhood for the internet. It is a test designed to be difficult for bots, but easy for humans.  While it does well in verifying humanness, CAPTCHA fails to verify uniqueness: as a human, you can pass as many tests as you want. This could be addressed by requiring everybody to solve a CAPTCHA challenge** at the same time**[8], but that would be very difficult to coordinate on a large scale. 

Many other approaches to Proof-of-Personhood[9, 10, 11] have been deployed. Some of these use social verification to ensure accounts are owned by unique humans. This often requires that existing users meet (physically or virtually) new users and deposit some form of financial stake that can be taken away in case of fraud. Social verification systems may lead to a robust Proof-of-Personhood, but they also face difficult scaling challenges.

Biometric approaches (e.g., Aadhaar in India) are promising as they are both accessible and enable accurately verifying uniqueness. The key challenges for biometric approaches are related to privacy, fraud detection, and scalability. We believe that recent advances in technology offer a way to solve these issues.

Worldcoin leverages biometrics, cryptography, and incentives to create a scalable, privacy-preserving solution to the “unique-human problem”. The following sections describe how the system works and details how we plan to deploy it globally.

At their core, biometric systems usually consist of:

1. A device that acquires biometric information (e.g., fingerprints) and converts them to a compressed representation (an “embedding”); and

2. A database that stores these embeddings for later retrieval and comparison.

Embeddings are designed so that one can calculate a distance (in the sense of similarity) between two embeddings. If this distance is above a certain threshold, the two embeddings are assumed to belong to different people.

One typically distinguishes between two modes of operation for biometric systems: verification and identification.

Verification is the most familiar use case of biometrics. For example, access to a building may require a keycard and a fingerprint scan. Here, fingerprint verification helps ensure that a stolen keycard cannot be used to enter the building. Behind the scenes, the keycard is linked to an embedding in the database, which is compared to the one of the scanned finger.

FaceID works in the same way. But instead of the user providing a keycard, the phone already knows which face(s) it needs to compare to as the database of users consists of only a single user.

In the case of identification, there is no keycard available to help: the biometric system has to determine a user’s identity from the biometric scan alone. A common use-case for biometric identification is in forensics where, for example, a fingerprint or DNA sample is compared with every entry in a database to identify a suspect.

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Fig. 2

Schematic explanation of the difference between biometric verification and identification:

While verification only requires comparison to a single piece of data, identification requires searching an entire database for a match.

A biometric system can be used as the foundation for Proof-of-Personhood by ensuring each person can only register once. Similar to biometric identification, the system needs to compare each user’s embedding to every other entry in the database. If none match, the user’s registration is successful and their embedding is added to the database. If there is a match, the user has likely registered before and is therefore rejected. 

However, there is a significant challenge with this approach: the identification problem becomes increasingly difficult with a growing database. Issues with search complexity and performance come into play, but more importantly, the system starts making more errors while trying to match users. These errors are largely governed by the “false match rate” (FMR). The FMR measures the likelihood that two biometric scans are incorrectly considered the same. At the scale of billions of users, the FMR must be extremely small to avoid frequently rejecting legitimate new users.

The key to being able to scale such a system to onboard billions of people is capturing an information-rich biometric source at a high level of fidelity. The more information the source contains, the lower the probability of false matches.

The likelihood of incorrectly rejecting legitimate new users is related to the Birthday Problem[12]: in a group of n randomly chosen people, how large should n be for two people to share the same birthday with a probability greater than 50%. The answer, 23, is counterintuitively low and demonstrates how likely random collisions are. In our specific implementation it turns out that the FMR has to decrease quadratically with the total number of expected users. To keep false rejections low at the scale of one billion users, the FMR needs to be below 1e-12 (that’s one in a trillion).

We evaluated many different technologies and believe that iris recognition is the best-suited for our biometric approach to Proof-of-Personhood. Compared to other biometric methods, like face recognition, fingerprints and DNA sequencing, iris recognition stands out by simultaneously satisfying the following three criteria: 

1. Uniqueness: The iris theoretically contains enough information to distinguish nearly all humans uniquely.

2. Fraud-resistance: The iris is difficult to physically modify and the biometric capture can be made hard to spoof.

3. Practicality: The required imaging technology already exists, and for the user, presenting their iris can be a fast and simple process.

On a global scale, a biometric uniqueness check must confidently distinguish each person from every other person. The information density of the iris is high enough to allow this, and no two irises are alike (even for identical twins). It also turns out that it is possible to capture most of this information with high-resolution imaging of the iris. 

The same is not true for today’s face recognition technology: at the scale of billions of people, there is simply not enough information in, for example, a selfie to reliably tell people apart. Even advanced algorithms such as neural networks can’t help. 

The information of the iris pattern is distilled into an embedding, in our case the so-called IrisHash, which is derived from a one-way function with the iris image as the input. This code is stored in a database and is the only data used for checking uniqueness. Under this approach, the original image of the iris does not need to be stored anywhere.

We describe this in more detail in our post on privacy.

We target an FMR of 1e-6 per eye (thus 1e-12 for both eyes combined). At a scale of one billion people, we estimate that around 0.05% of users will be accidentally rejected. We also target a false non-match rate (FNMR) of 1/7000, such that (on average) a user has to try signing up seven thousand times before they can register twice.

Using the iris also enables a strong degree of fraud-resistance. In the context of our biometric uniqueness check, this means we need to reliably detect if someone attempts to spoof the biometric capture (e.g., using animals or special contact lenses). Since cheating a uniqueness check only requires looking different than any existing user, the fraud resistance property of the iris is critical. The iris is inherently hard to modify and enables better ways to verify liveness compared to other common biometrics like faces and fingerprints.

Finally, any scalable uniqueness check must be fast and simple. From the user’s perspective, presenting an iris is as easy as posing for a photo. In fact, the practicality of iris recognition has already been proven at scale. One notable example is the border control system for the United Arab Emirates, which leverages iris recognition[13]. Some other biometric approaches, like DNA sequencing, may not provide the same degree of simplicity for the user, and can feel invasive.

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Fig. 3

Schematic representation illustrating the importance of high-quality imaging for decreasing error:

Here we sample pairwise comparisons by calculating the distances between embeddings. Since we  do this on an evaluation dataset, we know the ground truth and can plot the two distributions: the match distribution for pairs of the same identity (blue) and non-match distribution for pairs of different identity (red). 

In a perfect system, the match-distribution would be a very narrow peak at zero. However multiple sources of error widen the distribution leading to more overlap with the non-match distribution and therefore increasing False Match and False Non-Match rates. High quality image acquisition narrows the match-distribution significantly and therefore minimizes errors. The width of the non-match distribution is determined by the amount of information that is extracted by the biometric algorithm: the more information is encoded in the embeddings the narrower the distribution.

Using iris recognition for a scalable Proof-of-Personhood requires an iris scanner that’s secure, high-resolution, and easy-to-use. We searched for existing devices that meet these requirements at a global scale, but found none. For this reason, Worldcoin developed the Orb.

Fig. 4

A photo (not a render) of the Orb production model. The device has a diameter of 20 centimeters and weighs around 2.5 kg (5 lbs).  The surface of the Orb is mirror chrome. An LED ring guides the user through the sign-up process. Behind the black surfaces, the Orb has an eye-imaging system, infrared LEDs for illumination, and a fraud-detection system. An exchangeable battery is accessible from below to enable continuous mobile operation.

The primary function of the Orb is to capture detailed images of a person’s eyes, and convert them to an IrisHash. From the outside, the UX is simple: users simply look into the camera (which is behind the black surfaces) and press a button. On the inside of the Orb, a custom optical system automatically finds the user's eyes and brings them into focus. The Orb then captures high-resolution images of both irises at multiple infrared wavelengths, then uses them to locally compute the user’s IrisHashes.

To work at scale, the Orb must reliably capture high-quality iris images across a variety of lighting conditions and distances from the user. This adaptability is achieved using a combination of custom optics hardware and machine learning. To quickly find the user’s eyes, the Orb uses a movable mirror that is guided by a neural network. Once the eye is in-frame, another neural network controls a custom liquid lens to focus on the detailed patterns in the user’s iris. All of this happens while the Orb’s infrared LEDs are adaptively illuminating the eye, ensuring consistent images across lighting environments.

Together, these systems enable the Orb to capture irises with significantly higher quality: up to two orders of magnitude higher resolution compared to the industry standard[14, 15]. At this level of detail, the unique patterns in the iris can be used to reliably distinguish between billions of people.

To reduce complexity, the majority of commercial iris scanners today use goggles to align the subject precisely with the camera and block external light.

Fig. 5

On a high level, the Orb performs the following tasks:

Scan QR code
The device scans a QR code on the user's phone such that she can later prove that she has signed up.

**Capture Images
**After scanning the QR code the device captures multiple high-resolution multispectral images of the user.

**Generate IrisHash
**Based on the captured images, the device calculates a unique IrisHash through a one-way function.

Verify integrity
A custom set of security sensors ensures that the sign-up is legitimate.

Security is core to the Orb's design. After all, Worldcoin requires trusting that the IrisHashes are legitimately produced by an Orb. The Orb’s security system ensures the authenticity of each IrisHash by robustly detecting a wide range of fraudulent behaviors. Broadly, we can classify such behavior as either spoofing or tampering.

Unlike iris scanners used at border checkpoints, the Orb is deployed to unsecured environments and used by independent Operators. This is made possible by the Orb’s secure design, and is a key requirement for scaling Worldcoin.

Spoofing attacks involve presenting the Orb with modified, fake, or non-human irises. For example, an attacker might show the Orb a photo of an iris or an animal iris, hoping to generate a unique IrisHash. To defend against attacks like this, we’ve equipped the Orb with a suite of multi-spectral sensors and custom fraud-detection algorithms. This advanced anti-spoofing system complements the iris imaging system, and operates locally on each device.

The Orb is also resilient to various forms of tampering, including attempts to modify its software, extract its cryptographic secrets, or disable its anti-spoofing system. This resilience is critical, since any of these intrusions might allow a hacker to generate fraudulent IrisHashes. The Orb’s embedded systems reliably detect advanced attacks of this kind, and prevent corresponding fraud.

No biometric system is impenetrable to spoofing or tampering, given enough resources. That said, we’re confident that the Orb’s state-of-the-art security systems will prevent fraud deemed profitable for a would-be attacker.

To further increase the difficulty of an attack, Orbs will be remotely monitored and compared to other Orbs. Such monitoring is based on non-biometric metadata from the Orb, including battery level, temperature, and network strength. Anomalies will be flagged and lead to Orbs being deactivated. This anomaly detection happens in a controlled environment in the cloud and therefore comes with higher security guarantees than device-level spoof and tamper detection.

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Fig. 6

Left: Incentive model built around the Orb. Operators receive a  reward for each sign-up, incentivizing them to maximize their sign-up rate.

Right: Orbs are a scarce resource and must be allocated to the most efficient Operators. To this end, short-term contracts for operating the Orbs are allocated to Operators via a bidding process.

While the Orbs are important to solve the unique-human problem, it must also be ensured that those Orbs are used in the most effective way. Therefore, each Orb will be handled by the Orb Operator whose task it is to explain Worldcoin to new users and to operate the Orb to help them sign up. Operators receive a small reward(in Worldcoin) for each sign-up, which incentivizes them to maximize their *sign-up rate *(i.e., the number of sign-ups per week). Combined with the proof-of-personhood, this makes Worldcoin the first cryptocurrency to directly encode, into its trustless protocol, the economic incentives for users to join the network: giving every new user a share of its currency.

Cryptocurrencies like bitcoin typically pay miners for block production via issuance of its own currency. However, since Worldcoin and the Layer 2 are secured by the underlying Ethereum network, there is no need to incentivize miners or validators via the currency. Instead, the issuance of the currency can be directly allocated to users.

Still, one challenge is to find Operators that can actually achieve a high sign-up rate. This can be done at scale through a *bidding process *that allocates Orbs to the most efficient Operators. Concretely, Operators bid for the right to operate one or multiple Orbs for a defined period of time. Operators who sign up more users than others will achieve a higher monthly revenue, so they can be expected to submit higher bids, making them more likely to win the bidding process. Additional incentive structures are in place for promoting not only raw number of sign-ups, but also high-engagement of users and disincentivizing fraud. We will share more details about those mechanisms in the future.

The described incentive mechanism is core to Worldcoin. Out of the fixed supply of 10 billion tokens, twenty percent are used to fund Orb production and initial protocol development. But the rest and vast majority of the tokens will be given to users and Operators that are helping to launch Worldcoin through the protocol. Finally, to incentivize early adoption of the currency, the number of tokens that users and Operators receive per sign-up will decay over time.

With the Orb, Worldcoin aims to onboard the first billion users into the world of cryptocurrency. We believe Worldcoin can reach this unprecedented scale by leveraging recent innovations in blockchain scalability and embracing compatibility with the existing crypto ecosystem. This section details our approach, including the mechanisms for ensuring user privacy.

We expect most Worldcoin users to receive their account via the Orb, but this is not required. Anybody can create a Worldcoin account using any digital wallet built with our open-source SDK (see Wallet & SDK below). However, accounts created without an Orb do not receive free tokens at launch.

Worldcoin’s scalability is provided by an optimistic rollup[16, 17] on top of Ethereum. This "layer 2" scaling solution ensures transactions will remain cheap, fast, and reliable as the Worldcoin network grows. Importantly, this solution maintains the open and permissionless nature of Ethereum: anybody can create accounts, submit transactions, and participate in validation. The optimistic rollup is built using the open-source Hubble project[18], extended with a high-performance node that will be open-sourced in the coming weeks.

Worldcoin aims for broad compatibility. The underlying token is based on Ethereum’s popular ERC-20 standard, enabling compatibility with many existing tools and services. In addition, our open-source SDKs (see Wallet & SDK) will make it very easy for developers to interact with the currency and the Layer 2. 

Users are free to withdraw their funds to Ethereum mainnet or migrate through bridges to any Layer 2 on Ethereum (e.g., Optimism, Arbitrum, and many others) or even separate and aspiring ecosystems, such as Solana or Polkadot.

Fig. 7

Protocol architecture

1. The user generates a Semaphore public key and presents it hashed as a QR code to the Orb.

2. The Orb performs the iris scan and sends the created IrisHashalong with the Semaphore key to the current sign-up sequencer.

3. The sequencer validates the sign-up by checking the IrisHash for uniqueness in the database. If successful, it registers the Semaphore key on-chain.

4. The app locally generates a Hubble public key and submits it with a Semaphore zero knowledge proof to claim the reward.

5. The proof is verified and the reward is sent directly to the user’s public key in the Hubble rollup.

Worldcoin inherits Ethereum's privacy model: accounts are pseudonymous and transactions are public. Crucially, Worldcoin accounts are never associated with any biometric data from the Orb. Zero-knowledge proofs (ZKPs) are the enabling technology behind this privacy-preserving biometric approach. We use the open-source Semaphore[19] zero-knowledge proof system to transfer the uniqueness of IrisHashes to the uniqueness of user accounts, without linking them.

A zero-knowledge proof (ZKP) ensures a given statement is true, without disclosing any information about the statement (except that it's true). For Worldcoin, the "statement" is "this account is associated with a unique IrisHash". And that statement is either true or false. The corresponding IrisHash is never revealed. Recent advances in zero-knowledge proofs have made their use on smartphones practical.

Phase 1: Sign-up and uniqueness check

1. The user generates a Semaphore keypair on her phone

2. The user presents the hashed public key (via QR code) to the Orb.

3. The Orb scans the user’s irises and locally computes the user’s IrisHashes.

4. The Orb sends a signed message containing the hashed public key and the IrisHashes to the sign-up sequencer node.

5. The sequencer node verifies the Orb’s signature, then checks if the IrisHashes do not match any already in the database. If the uniqueness check passes, the IrisHashes and the public key are saved.

Phase 2: Claiming the reward

1. The user’s app locally generates a wallet address.

2. The app uses Semaphore to prove that it owns the private counterpart to one public key registered in phase 1. Because it’s a zero-knowledge proof, it does not reveal which public key.

3. The proof is sent again to the sequencer, which verifies it and initiates the deposit of tokens to the provided wallet address.

4. A so-called *nullifier *is sent along with the proof and ensures the user cannot claim the reward twice.

Those two steps - decoupled by the zero-knowledge proof - enable a biometric-based Proof-of-Personhood without linking user accounts to biometric data. A more visual explanation of account privacy can be found in our dedicated privacy blog post.

The "sequencer node" can operate trustlessly via optimistic verification in a smart contract. It also exists for optimization reasons. Users actually don’t submit proofs directly to a smart contract, but the sequencer first verifies and then batches them together with many other proofs.

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Fig. 8

**Privacy
**The whole process consists of two independent actions: Sign-up and Claim. The Orb sign-up links the IrisHash to the SemaphoreHash. This SemaphoreHash is never used publicly for anything that could be directly tied to the user. It is only used to prove membership within a set of registered users. However, this can be done through a zero knowledge proof that does not leak any other information about the user. This makes it possible for the verifier to check whether the user has signed up without knowing any identifiable information from the sign-up.

Worldcoin is designed to be the first widely-adopted cryptocurrency. Making this a reality means going further than having an inclusive launch: Worldcoin must be useful and understandable to people with no prior experience using digital money. In addition, users must be confident in the privacy and security of their accounts. Because of this, we are developing a mobile wallet application.

The wallet allows users to learn about Worldcoin and other cryptocurrencies, find Orb Operators, claim their share, view their balance, send global peer-to-peer payments, and use their Worldcoin throughout the Ethereum ecosystem. No central authority mediates transactions; users always have full control and ownership of their Worldcoin (i.e., the wallet is “non-custodial”), which they can back up if they choose.

Fig. 9

**Wallet
*****Illustrative wireframe, not actual product images.
*For most people, Worldcoin will be their first contact with a cryptocurrency, and for some, their first with any kind of digital money. The applications of crypto are far bigger, but as the initial use-case for first-time users, the wallet will enable instant peer-to-peer payments to anyone in the world.

In addition to the wallet, we are developing a collection of open-source Software Development Kit (SDKs) to help developers build products around Worldcoin—things like alternative clients, tools for niche use-cases, digital tipping, in-store payments, and professional interfaces. These SDKs, coupled with pre-existing decentralized financial protocols, will allow anyone to serve the needs of local, regional, and global markets.

Most excitingly, these SDKs will eventually include zero-knowledge Proof-of-Personhood for third-party applications, maintaining user privacy as described in the Account Privacy section. While we built the Orb to help make Worldcoin a reality, we know this primitive can unlock much more. That’s why we want to give everyone the ability to reuse their already issued proofs to access other projects.

We believe the wallet and SDKs will help make Worldcoin — and the larger crypto ecosystem — more accessible and useful. We’re excited to share more details about these tools over the coming months.

There are many ways in which Worldcoin can have substantial positive effects on our society. Still, we strongly believe that how we accomplish this project is just as important as what we achieve. Our design approach is based as much on our own deeply-held values as on technical reasoning. We are choosing to prioritize user privacy, data security, openness, and broad accessibility, even when it means tackling some of today's toughest engineering and operational challenges.

For example, building on Ethereum at this scale is more challenging than operating a custom, centralized blockchain, at least in the short-term. The same applies to the privacy approach using zero-knowledge proofs, which is on the edge of current research. But we think this is the right way to launch Worldcoin, and the effort will pay off in the long run for all of us.

If successful, Worldcoin will, within the first year, onboard hundreds of millions of new people who didn’t have access to this technology. This will hopefully result in many developers integrating Worldcoin into new and existing products. We believe the internet has entered a new era: web3, where finally economic value and ownership are natively integrated into the web. It is hard to imagine what new products this coming era will bring us. Certainly, it will involve wider adoption of novel technologies and models of collaboration, like DAOs, NFTs, and decentralized exchanges.

There’s still a lot of work to do to enable and support a rapidly sprawling ecosystem of developers, entrepreneurs, and community builders. We are in the early stages of designing Worldcoin’s long-term governance strategy, grant programs, and partnerships roadmap. We are committed to following credible neutrality[20] as a key guiding principle in setting up these mechanisms. 

There are still many challenges left, and we will continue our research on many of them, such as blockchain scalability, digital identity, and pseudonymous economies.

Join us and let’s build together!

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