Polygon ID Overview

Source: https://university.polygon.technology/pid.png

Introduction

Lets dive into identity space to understand what is the current landscape of identity and how its being currently used.

Following section lists down the 3 major identity offerings currently exists with their examples, features.

1. Centralized Identity (CI):

This is a form of identity offering wherein a user registers on each platform inorder to use the services that they offer.

Features:

1. Single purpose and siloed: These identities are single purpose and siloed meaning user will have to go through a sign up process again with setting up of usernames and passwords to access new application.
2. Managing logins: Since user needs to signup to different applications with different usernames and passwords it creates a overhead for user to manage those usernames and passwords.
3. Fragmented Identity: In this case the identity resides on the app infrastructure i.e. usernames password that user sets is stored in service providers datastore. So users identity is scattered all over different services.

Common examples of services that support such Centralized Identity approach include passport registration portals etc.

2. Federated Identity(FI):

This is a form of identity offering wherein a user registers on each platform inorder to use the services that they offer using 3rd party identity providers like Google.

Features:

1. Multi purpose Identity: Federated identities like google, facebook can be used across different services
2. Account Reusability: Single federated account can be used across different services, thus these identities are more portable
3. Data Ownership: In this case too identity resides with big tech giants/ identity providers like google facebook.

Common examples of services that support such Federated Identity approach include Medium app/portal, LinkedIn etc.

3. Self Sovereign Identity (SSI)

This is a form of identity offering wherein a user maintains his own identity and presents the same as and when required to access different services without involvement of 3rd party identity providers like Google.

Features:

1. Multi purpose Identity: Self Sovereign identities can be used across different services
2. Account Reusability: Single identity/account can be used across different services, thus these identities are more portable
3. Data Ownership: In this case identity resides with identity owner i.e. user itself manages the identity

For all above 3 approaches incase of Centralized identity and Federated identity data is in control of third party whereas the Self Sovereign identity gives identity in control of the user and eliminates the 3rd party and also limiting the amount of data exposed to any services by creating dynamic identity proofs to prove that you hold the identity. (which is achieved using cryptographic ZK proofs)

Polygon ID

Introduction

Now lets understand why we need SSI and where Polygon ID helps in this SSI journey. Common scenarios which can be seen recently asking for private information like birth date are listed below:

1. Facebook: During the sign-up process, Facebook asks for your birthday so that it can create a personalized experience for you and show you content relevant to your age.
2. Instagram: Instagram also requires you to enter your date of birth during registration. This is to ensure that users are above the age of 13 and comply with the Children’s Online Privacy Protection Act (COPPA)
3. Spotify: When you sign up for a Spotify account, you’re asked for your date of birth to help personalize your experience
4. Uber: When you sign up for Uber, you’re asked for your date of birth to ensure that you’re over the age of 18 and meet the minimum age requirement to use the service.

As you can see above, user needs to share his/her personal information inorder to access these services. Here’s where SSI comes in wherein SSI gives user power to share only required information and to what extent (i.e. user will only share a proof that he is above the required age say above 18 and will not share actual birth date). For implementing this Polygon ID provides toolkit to build such a decentralized identity systems where all entities in ecosystem namely Issuer, Verifier and Holder can interoperate to create SSI based ecosystem.

Features

Polygon ID as described above is scalable blockchain based decentralized identity with ZK based privacy.

1. Decentralized: Users are in control of their identity eliminating 3rd party giants like Google.
2. Private by default: Polygon ID employs ZK based privacy in creating proofs which are shared with verifiers
3. Trust and reputation: Polygon ID allows user to use identity attributes to create claims inorder to create complex proofs to be shared with verifiers.

Note: claims refers to any fact about the identity examples include claim created using date of birth which states person is above 18years without revealing actual birth date

4. Open and permissionless: Any person can be issuer on the network as well as anyone can play the role of the verifier on the network and doesn’t need to rely on issuer for proof verification. Also holder doesn't need 3rd party intervention to submit the proof to verifier.

Offerings

1. Privacy using Zero-Knowledge Proofs: Polygon ID enables user to present zk proof of the verifiable credential for the requested verification request without actually handing out the actual credential to verifier
2. Off-Chain and On-Chain Verification: Verifier can opt in for off-chain or on-chain (via Smart Contracts) verification of proofs.
3. Self-Sovereignty: Polygon ID makes identity in control of the user, thus user can share it with any entity within decentralized identity system without requiring issuers consent

Core concepts

1. DID: Every identity is identified by a unique identifier called DID (Decentralized Identifier). Private public key pairs associated with this DID is created with Baby Jubjub algorithm. This type of key is designed to be efficient while working with zkSNARKs.
2. Verifiable Credentials: Every identity-based information is represented via a Verifiable Credentials (VCs). These credentials includes identity attributes(name, birth date etc) and proof associated with it which makes it verifiable credential.

The architecture of the framework is composed of three entities: Identity Holder, Issuer, and Verifier. These three, together, form what we call the triangle of trust.

1. Identity Holder: An entity that holds claims in its Wallet. A verifiable credential, is issued by an Issuer to the Holder. The Identity Holder generates zero-knowledge proofs/claims of the verifiable credential and sends these proofs to the Verifier, for proof verification.
2. Issuer: This is a trusted entity that issues cryptographically signed verifiable credential to the Holders.
3. Verifier: A Verifier verifies the proof presented by a Holder. Here verifier performs number of checks one is it checks the signature of the issuer secondly it checks if proof satisfies the requested requirement (for eg: persons age is above 18).

This is where triangle of trust exists between above 3 entities. Holder proving verifiable credential claim using cryptography doesn’t mean verifier can accept it as is, verifier needs to have a trust on signing authority i.e. issuer of credential to accept it.

Polygon ID is build on iden3 protocol and it provides abstraction layers over this protocol so developers can leverage these tools to create decentralized identity ecosystem comprising of issuers, validators and identity holders.