Since Proof of Humanity is mentioned in some of Kleros’ materials as a mechanism of Sybil resistance for juror sets, we provide a brief description here.

Overview

Proof of Humanity (or PoH) is a social identity verification system for humans on Ethereum. PoH combines webs of trust, reverse Turing tests, and dispute resolution to create a Sybil-proof list of humans.

To submit a profile in PoH, one will need to provide:

1. Display Name, First Name, Last Name: Submit your full name.
2. Short Bio: Include a concise personal description.
3. Photo of Your Face:
   • A clear, face-forward photo with visible facial features.
   • Avoid heavy make-up, large piercings, or masks that obstruct facial recognition. Usual wear like headscarves or turbans are acceptable, but not special occasion items.
4. Video with Face and Eth Address:
   • Display full Ethereum address (no ENS or ellipsis). The sign can be a screen, and it should be in the correct orientation for reading.
   • Verbal certification in English, affirming you're a real human and not already registered.
   • Video requirements: up to 2 minutes, in video/webm, video/MP4, video/avi or video/mov format, vertical, horizontal, or square; minimum height and width of 352 pixels.
   • Quality of the video:
     • Lighting and recording quality should allow clear discernment of facial features and Ethereum address.
     • The audio quality should be clear enough for easy understanding.
     • The face should meet the same requirements as the photo.
     • Ensure the video preview works well before submission.
5. Deposit:
   • An ETH deposit of 0.125 is required to deter fake or spam accounts. If a profile is challenged and deemed 'invalid' by Kleros jurors, the deposit will be forfeited.
   • deposit can be crowdfunded
6. Vouching and Challenges:
   • Users can challenge submissions they think don't meet the requirements by submitting a deposit.
   • Challenges can be for incorrect submissions, deceased submitters, duplicates, or non-existent submitters.
   • Disputes go to an ERC-792-compliant resolution system, initially Kleros.
   • Winning a challenge sends the submission back to “pending” mode for potential further challenges (though the same reason can't be used twice).
   • Parallel challenges are possible for duplicates.
   • Users should vouch for people they know in real life. Vouching is not financially incentivized.
   • Users can withdraw their vouch at any time.
   • The required number of vouches is decided through governance.
   • Vouching for already registered users is possible and useful close to expiration.
7. Disputes & Removal Requests:
   • Removal requests can be submitted at any time with a deposit.
   • If unchallenged, the individual is removed. If challenged, the case goes to dispute.
   • Successful removal doesn't affect those who vouched for the user.
8. Universal Basic Income (UBI):
   • UBI is a token given to all successfully registered users on PoH, streamed to each account every second.

How a profile gets accepted

Diagram description of the process for submitting an identity

Problems

1. The system's requirements for an individual to submit a photo and a video may prove insufficient as deep fake technology advances, and creating realistic images and videos of non-existent people is becoming easier. Consequently, these false identities could infiltrate the system, presenting multiple fake persons as genuine users.
2. Another concern is the potential for exploiting individuals unfamiliar with the blockchain space. An individual could cheaply recruit others to create identities, instructing them to post photos and videos on their behalf. This presents a way for creating illegitimate identities within the system.