Authentication Mechanisms: JWT, OAuth, and Single Sign-On (SSO)

Tấn Trương — Thu, 23 Apr 2026 02:35:34 +0000

Introduction

In modern application development, securing user authentication is a foundational requirement. As systems scale and threats become more sophisticated, choosing the right authentication and authorization strategy becomes critical.

Three widely adopted approaches are JWT (JSON Web Token), OAuth 2.0, and Single Sign-On (SSO). While often mentioned together, they solve different problems and are frequently used in combination.

This article provides a clear, practical comparison along with system flows and best practices.

Authentication vs Authorization

Before diving deeper:

Authentication: Who are you?
Authorization: What are you allowed to do?

A secure system must enforce both.

JWT (JSON Web Token)

What is JWT?

JWT is a compact, URL-safe token used to transmit claims between client and server. It is commonly used for stateless authentication.

Structure

A JWT consists of three parts:

Header.Payload.Signature

Header: Algorithm (HS256, RS256)
Payload: Claims (user_id, role, exp)
Signature: Integrity verification

Flow

User → Login → Server
Server → Generate JWT → Client
Client → Attach JWT → API
API → Verify JWT → Response

Pros

Stateless (no session storage)
Scales well in microservices
Fast verification

Cons

Hard to revoke
Token leakage risk

Best Practices

Short-lived access tokens
Use HTTP-only cookies
Avoid sensitive payload data
Implement refresh token strategy

OAuth 2.0

What is OAuth?

OAuth 2.0 is a protocol for delegated authorization. It allows applications to access user data without exposing credentials.

Roles

Resource Owner (User)
Client (App)
Authorization Server
Resource Server

Flow

User → Login + Consent → Authorization Server
Authorization Server → Access Token → Client
Client → API Request → Resource Server
Resource Server → Validate Token → Response

Grant Types

Authorization Code (recommended)
Client Credentials
Implicit (deprecated)
Password (legacy)

Best Practices

Use Authorization Code + PKCE
Never expose client secret
Validate redirect URIs
Use refresh tokens

Single Sign-On (SSO)

What is SSO?

SSO allows users to log in once and access multiple applications without re-authentication.

Flow

        [ SSO Provider ]
               │
     ┌─────────┼─────────┐
     ▼         ▼         ▼
  App A     App B     App C

Technologies

SAML (enterprise)
OpenID Connect (modern, built on OAuth)

Pros

Better user experience
Centralized access control

Cons

Single point of failure
Higher complexity

Best Practices

Enforce MFA
Implement RBAC
Monitor and audit logs

Comparison Table

Criteria	JWT	OAuth 2.0	SSO
Purpose	Authentication	Authorization	Central Authentication
State	Stateless	Token-based	Session-based
Use Case	APIs, microservices	Third-party access	Multi-app systems
Complexity	Low	Medium	High
Scalability	High	High	Medium
Revocation	Difficult	Managed by auth server	Centralized

Real-World Architecture (Recommended)

Client
  │
  ├── Access Token (JWT - short-lived)
  ├── Refresh Token (stored in DB)
  │
Backend
  ├── Verify JWT
  ├── Manage session / revoke
  ├── Integrate OAuth providers
  │
SSO Provider (optional)

Key Ideas

Use JWT for performance
Store refresh tokens in database (revocable)
Route all API calls through backend
Track device/session for security

Conclusion

There is no one-size-fits-all solution:

Use JWT for stateless APIs
Use OAuth 2.0 for third-party integrations
Use SSO for unified login across systems

In practice, modern systems combine all three to achieve both security and scalability.

DEV Community: Tấn Trương

Authentication Mechanisms: JWT, OAuth, and Single Sign-On (SSO)

Introduction

Authentication vs Authorization

JWT (JSON Web Token)

What is JWT?

Structure

Flow

Pros

Cons

Best Practices

OAuth 2.0

What is OAuth?

Roles

Flow

Grant Types

Best Practices

Single Sign-On (SSO)

What is SSO?

Flow

Technologies

Pros

Cons

Best Practices

Comparison Table

Real-World Architecture (Recommended)

Key Ideas

Conclusion