Polygon ID is More than Biometric Proof of Personhood

Polygon Labs
August 17, 2023
Image source: Dribbble


  • Polygon ID is open source technology that can enable decentralized identity
  • The Polygon ID protocol supports a variety of identity verification methods, from documents to biometrics and more
  • The goal of Polygon ID is to enable a self-sovereign identity (SSI) layer for the web
  • Biometric “proof of personhood” schemas issue credentials proving uniqueness, but are not fundamental identity layer protocols

A big h/t to Vitalik Buterin's compelling and thoughtful approach to credentialing and biometric proof of personhood in “What do I think about biometric proof of personhood?” which inspired some of the thinking for this blog.

Identity Is a Classically Hard Problem

“Who are you?” 

Norwegian writer Jostein Gaarder opens Sophie’s World with this seemingly simple question. But as Sophie tries to answer, she runs into the hardness of identity. Is she the same Sophie when she ages, when the cells in her body die and are replaced by new cells? Is she the same Sophie talking to her mother as she is when she’s talking to her best friend? 

The internet only exacerbates these problems of identity–who are you?–which grows tangled and confusing in the analog/digital divide. One person, many platforms. Identity is fractured online.

To be online and to prove you are you requires meeting at least a couple of conditions: 

  1. Proof of Personhood (PoP) or Proof of Uniqueness (PoU): In a digital environment, this is a long-lived credential that states you are a unique human. Offline, you are uniquely you, always. What protocol can demonstrate that same uniqueness on the web?
  2. Proof of Humanity: Proof of Humanity is a brief, momentary action taken, for example, during a form fill-out or authentication process. This demonstrates that you are not a bot. It serves as verification in a particular interaction to confirm that you are a real human user and not an automated program.

Polygon ID is an open-source toolset that enables developers to build solutions for the hardness of identity, to meet the above conditions. It is infrastructure for a self-sovereign identity layer of Web3.

On the other hand, there are issuers of biometrics proof-of-personhood credentials that rely on processes like uploading videos of one’s face or eye-scanning–but these issuers are not identity architecture. They meet the first criteria, but not always the second, and they are not general infrastructure for an identity protocol in the same way as Polygon ID.

Let’s take a peek at the differences.

What’s the difference between an issuer and infrastructure?

Polygon ID is an identity protocol, open source technology that can help create a self-sovereign identity layer for Web3. It is a set of tools that allow actors in Web3 to implement decentralized identity, composed of three possible roles: 

  • Issuers of credentials, such as governments, universities, certification agencies, KYC providers, private companies, or a social graph in which people can make statements about others, etc;
  • Identity holders, the users that hold credentials issued to them in a wallet or vault;
  • Verifiers, who are entities or people that use or consume information from the user’s credentials, usually dApps.

The objective of Polygon ID technology is to enable an ecosystem for decentralized, self-sovereign identity, supporting a variety of identity verification methods, whether that’s with identity document verification methods, biometrics, or others. 

Because Polygon ID is an open-source codebase, there is currently no issuer of credentials, and therefore no central entity directly manages personal information.

In contrast, biometric proof of personhood are credentials, utilizing biometrics technology. This might be eye scans or other kinds of biometric data, such as face-video-uploads and verification games. 

Often, issuers will store hashes of users’s biometrics data in a centralized database. 

Flexibility of Identity Verification Methods

“There is no ideal form of proof of personhood,” Vitalik Buterin argues in his post about biometrics verification. Instead, he claims approaches should be flexible enough to respond to a rapidly evolving sector. Different designs can be used for solving the tricky problems of identity verification. 

The Polygon ID protocol is flexible enough to respond to whichever methods become popular over time. Governments will continue to issue credentials, even as cryptographers design biometrics-based or social-graph solutions. Polygon ID can accommodate a variety of verification methods. 

Open Source Ethos and Transparency

Polygon ID is open source, with Apache / MIT Licenses, which enables developers to propose improvements and audit the code. In addition, collaborations with Rarimo identity bridging technology means that Polygon ID credentials can be validated across other EVM chains (Ethereum mainnet, Avalanche, Optimism, and so on).


Learn more about Polygon ID and get in touch with the team today! Tune into the Polygon Labs Blog and our social channels to keep up with updates about the Polygon ecosystem.

Together, we can build an equitable future for all through the mass adoption of Web3!

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