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Identity Protocol: A Deep Dive into OpenID Connect (OIDC)

SA
Security Analyst
Resource Specialist

Core contributor to the Niche Resource Directory ecosystem, specialized in data curation and information architecture.

2026-03-21
11 min read

Identity Protocol: A Deep Dive into OpenID Connect (OIDC)

OAuth 2.0 is for Authorization (accessing a resource). OIDC is for Authentication (proving who you are).

The ID Token

The core of OIDC is the ID Token, a signed JWT that contains user "Claims" (Email, Name, Profile). Unlike an Access Token, the ID Token is meant to be read by the client.

The Flow of Trust

  1. Authorization Request: Client asks the Identity Provider (IdP) for identity.
  2. User Consent: User signs in via a secure SSO page.
  3. Token Exchange: Client receives an ID Token and verifies its signature using the IdP's public keys (JWKS).

Security Best Practices

  • Always use the 'Authorization Code' flow with PKCE.
  • Never store ID Tokens in LocalStorage (use Secure/HttpOnly cookies).
  • Validate the 'aud' (Audience) claim to prevent token replay attacks.