Exploring Anti-Sybil Approaches: Proof of Humanity Protocol

The internet is under siege, not by hackers or malware, but by an overwhelming flood of bots and AI-generated content. Forget "decentralization," forget "blockchain revolution."Every online community, crypto or not, faces the same challenge: distinguishing real humans from fake ones.  This is about basic online trust. Fake accounts can rig votes, loot rewards meant for real people, and turn social platforms and apps into spam-filled nightmares. In 2024, over half of all web traffic was attributed to bots, signaling a significant shift in online interactions. 

With all this, proving you’re a unique human online still feels frustrating: endless CAPTCHA puzzles, invasive ID checks, or handing over your info to big corporations just to access basic services.

At Humanode, we've always believed in something genuinely different: Sybil resistance without sacrificing decentralization, identity checks without losing privacy, and uniqueness proofs that don't rely on big brother databases. But we aren't the only ones raising concerns over this tricky terrain. Proof of Personhood (PoP) has gone mainstream; Vitalik’s been blogging about it, Elon’s tweeting about it, and even A16z is investing in it. Especially, Web3 isn’t just knocking on the door anymore. It’s standing on the porch, asking for a better way to verify humans.

Naturally, at Humanode, we have been working on solving this problem for years and are one of the pioneers in Anti-sybil technology. We believe that our cryptobiometric tech and Biomapper system offer a path to Sybil resistance without giving up decentralization or privacy. But let’s be honest: no one project can solve this alone. The fight against Sybils is a collective one, and different approaches may solve different parts of the puzzle. That’s why we’re taking a step back to examine the landscape, not as competitors, but as collaborators in the same mission.

That's why we've kicked off this series: to explore how different anti-Sybil platforms handle proof of personhood, not just from a theoretical angle, but by looking at how they practically work, what kind of tech they rely on, how decentralized they are, and what real users think of them.

In this first article, we're shining a spotlight on Proof of Humanity Protocol (PoH), an Ethereum-based registry of real, unique humans that uses social vouching.

Let’s walk through how PoH works, discuss its decentralization model, and reflect on what it's really like for everyday users to interact with.

The goal here isn't to rank solutions or suggest who’s doing it better. Instead, it’s about learning, understanding, and identifying valuable insights that might help us all build a fairer, more decentralized future.

What is PoH?

Built by Kleros and Democracy Earth, PoH was created to fight bots while keeping things decentralized and privacy-friendly. It is a decentralized, Ethereum-based registry designed to verify that each participant is a unique, living human. It combines social verification with video submissions to create a Sybil-resistant list of humans.

The verification process involves a combination of social attestations and decentralized arbitration. Users submit a video and are vouched for by existing members. If disputes arise, they are resolved through Kleros' decentralized court system, ensuring fairness and transparency. 

What can you do with it?

1. Universal Basic Income (UBI):

PoH started as a way to distribute crypto-based UBI tokens. If you’re verified, you get paid just for existing.

2. DAO Governance:This verification supports fair voting mechanisms, such as one-person-one-vote systems, no whales with 100 wallets. No farmed addresses.

3. Quadratic Funding: Useful for grants and public goods funding. PoH helps prevent Sybil exploits by making sure each donation comes from a real, single person.

Apart from these major use cases, it can be used for other important purposes like building Decentralized P2P marketplaces, social media platforms, and more, where Sybil resistance is required.

Positioning PoH in the Ecosystem

PoH stands out in the digital identity ecosystem by prioritizing community involvement and decentralized verification. Its integration with platforms like Gitcoin Passport, use in various online gamification platforms, and in various DAOs highlights its versatility and effectiveness in real-world applications.

By focusing on social verification and decentralized arbitration, PoH offers a compelling alternative to more centralized systems. Its emphasis on privacy, inclusivity, and community governance positions it as a valuable tool in the ongoing effort to establish trustworthy digital identities.

Architecture

PoH leverages Ethereum's smart contract capabilities to ensure transparency, immutability, and decentralization. Here's how the system manages data:

• Ethereum Smart Contracts: The core logic of PoH is encoded in Ethereum smart contracts, primarily written in Solidity. These contracts handle the registration process, vouching, challenges, and arbitration outcomes. Once deployed, these contracts are immutable, ensuring consistent and tamper-proof operations.
• Data Storage: User-submitted data, such as videos and profile information, is stored off-chain using the InterPlanetary File System (IPFS). This decentralized storage solution ensures that data remains accessible and resistant to censorship while keeping the Ethereum blockchain uncluttered.
• Transparency and Verifiability: All actions within the PoH system, from registrations to challenges, are recorded on the Ethereum blockchain. This transparency allows anyone to audit the registry's operations, fostering trust in the system's integrity.

Decentralization and Governance in PoH

In Web2, and even in centralized Web3 platforms like centralized exchanges, you prove who you are through companies like Google, Meta, or by handing overa government-issued ID. That works, until it doesn’t. One hack, one leak, and your identity is out there.  Plus, you’re always trusting someone else to manage your digital self. Recent Coinbase breach is the prime example of this.

PoH flips that.

No centralized gatekeeper. No admin who can delete your account. You join PoH by being vouched for by another human and having your registration stored on the Ethereum blockchain.

Vouching is the backbone here. It's like saying, "I know this person is real," and putting a bit of your own reputation on the line. No one gets in without that trust handshake.

Now, if something goes wrong, maybe someone fakes a video or tries to slip through twice, that’s where Kleros steps in. It’s a decentralized court where random peers judge the dispute. No company, no CEO, just other users with a stake in keeping things fair.

Back in 2022, PoH even switched the staking mechanism to use the UBI token instead of ETH. That way, the community that actually uses the system has more say in how it runs.

But let’s not pretend it’s all smooth sailing.

• It’s hard to get vouched for if you don’t know anyone.
• Some Kleros juries make weird calls.
• And running a system like this takes constant community involvement, or it starts to wobble.

Still, this is decentralization in action. Messy, open, and trying to put power in the hands of real people, not just software or institutions.

What’s it like as a user?

So let’s say you want to get verified. What does that actually feel like?

First, you make a short video. You read a sentence, show your Ethereum address on a piece of paper, and upload it. That video goes onto IPFS, which means it’s public and permanent. Yep, forever.

Next, you need a voucher, someone who’s already verified on PoH. If you’re new to the community and don’t know anyone, that part can be a serious hurdle.

Then comes the waiting game. Your profile goes up for a challenge period, where anyone can contest your submission. If that happens, you go to Kleros. A jury of users will vote on whether your profile looks legit or not.

If you pass? Congrats. You’re now on the registry.

If not? You lose your deposit, and you’re back to square one.

Now, the system’s fair in theory, but users have pointed out a few pain points:

• Getting a voucher is hard if you don’t have connections.
• The challenge process can be confusing, especially if you’ve never used Kleros before.
• Gas fees and deposits can add up fast, sometimes reaching $600+ just to get through the door.
• The requirement to upload personal videos to a public, immutable ledger raises concerns.
• Technical hurdles for non-blockchain users.

Efforts are underway to address these issues, such as exploring layer 2 solutions to reduce costs and integrating privacy-preserving technologies like Semaphore to enhance user confidentiality.

In summary, while Proof of Humanity protocol offers a novel approach to establishing digital identity and combating Sybil attacks, it must overcome significant user experience challenges to achieve broader adoption and inclusivity.

Current Adoption Landscape

Since its inception in 2021, one of the notable applications of PoH has been its integration with Universal Basic Income (UBI) initiatives. Registered users receive UBI tokens, providing a form of passive income. This approach has been particularly impactful in regions with limited access to traditional financial systems. Beyond UBI, PoH has been explored for various use cases. 

Limitations and Areas for Improvement

That said, it’s far from perfect. The same decentralization that makes PoH trustworthy also creates barriers to scale:

• Manual effort: Verifying every new user requires time and trust from other humans.
• Scalability issues: Vouching and arbitration aren’t designed for high-speed mass onboarding.
• Privacy concerns: Public video uploads can deter users concerned about surveillance or doxxing.
• Gas fees: On Ethereum mainnet, it can cost hundreds of dollars to register, challenge, or interact with the system.
• Network effects: For someone new to crypto or without any connections, getting vouched is often the hardest part.

In short, PoH works, but it’s not plug-and-play. It requires time, social capital, and some technical knowledge, which can leave many potential users behind.

In the final section, we’ll wrap up this deep dive, reflect on what PoH teaches us about decentralized identity, and preview the next project in our series.

Conclusion

Proof of Humanity Protocol isn’t just an experiment in Sybil resistance, it’s a bold, public attempt to prove that we can verify people without turning the internet into a surveillance state.

It shows that decentralized identity doesn’t have to mean government-issued documents. It can mean community-driven validation, transparent arbitration, and systems where trust is earned, not bought.

Through our deep dive, we’ve seen the technical foundation, Ethereum smart contracts, vouching, and Kleros courts. We’ve walked through the user experience, the highs of UBI and DAO participation, and the lows of gas fees and public exposure. And we’ve explored what works, what doesn’t, and where PoH could go from here.

But most importantly, PoH has helped shift the conversation. It pushed Proof of Personhood from theory into reality. And while it’s not perfect, it’s out there, verifying real people on-chain, without needing anyone’s passport or driver's license.

That’s why PoH deserves a place in the broader movement toward a Sybil-resistant Web3.

It’s not about who’s “winning” the identity wars. It’s about building alternatives to the centralized status quo. And PoH, flaws and all, is a working piece of that puzzle.

In the next article of this series, we’ll take a closer look at Worldcoin, a radically different approach that uses biometric orbs and zero-knowledge proofs to verify identity at scale. What lessons does Worldcoin’s high-tech model offer? Where does it shine, and where does it stumble? And how does it compare to community-based models like PoH?