Worldcoin

Abstract	Privacy-preserving Proof of Personhood. They have not launched yet but have a unique approach to building a Sybil-resistant on-chain identity system, using hardware to distinguish between humans.
Year	2021
Link to the paper	https://id.worldcoin.org/about/protocol
Relevance score	Maybe relevant
Quality score	4
Labels	Possible tool in larger solutionSybil resistance insights

Worldcoin aims to provide an identity protocol, using a hard fork of semaphore that can be used as proof of uniqueness. It creates a "world ID" by taking an image of the eye's iris with specialized hardware.

When a user executes a World ID transaction, two things must be proven:

The user is a human

The user is acting only once

To provide Proof of Personhood, the protocol makes use of a hardware called "The Orb", which takes the image of an eye's iris and only stores it in RAM. From a hash of the image and zero-knowledge proof, an identity can be created.

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. A 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. Source https://worldcoin.org/how-the-launch-works#rf2

Furthermore, Worldcoin aims to achieve proof of uniqueness by utilizing actions that produce the same output hash for the same identity. For example, Alice wants to claim an airdrop. To receive this airdrop Alice has to provide a ZK proof associated to an "Action ID", that outputs a nullifier hash that can be stored by the airdrop provider and can't be related to Alice's ID.