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Primitives/Primitive #20
PRIMITIVE #20Core Distributed Systems Component

OAuth 2.0, OIDC & Distributed Token Authentication

1. What It Is & Why It Exists

The Core Problem: Delegated Authorization vs. Authentication

In distributed architectures, microservices must answer two fundamental security questions:

  1. Authentication (AuthN - "Who are you?"): Verifying identity. Solved by (), an identity layer built on top of OAuth 2.0 that provides standardized ID Tokens (id_token).
  2. Authorization (AuthZ - "What permissions do you have?"): Delegating access rights to third parties without sharing user passwords. Solved by OAuth 2.0, which issues scoped Access Tokens (access_token).
Interactive Architecture Diagram
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2. OAuth 2.0 Authorization Code Flow with PKCE

For Single-Page Applications (SPAs) and mobile clients that cannot securely store client secrets, PKCE (Proof Key for Code Exchange - RFC 7636) is mandatory to prevent authorization code interception attacks.

Interactive Architecture Diagram
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3. Token Formats & Cryptographic Comparison

Comprehensive Comparison Matrix

FormatStructureSignature / EncryptionPayload Tampering DefenseRevocation MechanismLatency Overhead
Stateful Session ID128-bit Opaque UUIDNone (Lookup Key)Server-side storage validationImmediate (DEL session:uuid)1−3 ms1 - 3\text{ ms} ( read per RPC)
JWT (RS256 / EdDSA)Header.Payload.SignatureAsymmetric Public Key (RS256 / Ed25519)Cryptographic signature verification / blocklist / Short <0.1 ms< 0.1\text{ ms} (Local CPU verification)
PASETO (v4.public)v4.public.<payload>.<sig>Ed25519 (No alg: none exploit)Built-in Authenticated Encryption (AEAD)Short + Refresh token rotation<0.1 ms< 0.1\text{ ms} (Local CPU verification)
Passkeys / WebAuthnFIDO2 Authenticator AssertionECDSA / RSA Hardware KeyPhishing-resistant challenge-responsePublic key de-registrationNative OS / Secure Enclave

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