Building a secure user identity system is one of the most critical responsibilities of any software developer. A single vulnerability in your login logic can expose sensitive customer data and lead to security breaches. To help you implement robust defenses, we have compiled this authentication cheat sheet outlining modern web security standards.
In this authentication cheat sheet, we will discuss the difference between authentication and authorization, analyze secure password hashing algorithms, explain multi-factor authentication (MFA), and compare session-based and token-based storage.
Authentication vs. Authorization
Before designing your security layer, it is vital to separate these two concepts:
- Authentication (AuthN): Verifies *who* the user is (e.g., username, password, biometric scan, or security token).
- Authorization (AuthZ): Verifies *what* the authenticated user is allowed to do (e.g., admin permissions, read/write roles).
1. Secure Password Storage & Hashing
Under no circumstances should passwords be stored in plain text. Furthermore, traditional fast hashing algorithms like MD5, SHA-1, or SHA-256 are no longer safe for passwords because modern GPUs can perform billions of guesses per second.
Instead, use **adaptive, memory-hard hashing algorithms** designed to slow down attackers:
- Argon2id: The current industry-recommended standard (winner of the Password Hashing Competition). It offers strong resistance against GPU and ASIC hardware attacks.
- bcrypt: A reliable, widely supported alternative that uses a configurable work factor to scale with hardware improvements.
- Always Salt: Ensure a unique, cryptographically secure random salt is generated and appended to the password before hashing to prevent rainbow table attacks.
2. Multi-Factor Authentication (MFA)
Passwords alone are vulnerable to phishing and credential stuffing. Implementing MFA provides an extra layer of protection:
- App-Based TOTP: Use Time-based One-Time Passwords generated by apps like Google Authenticator or Authy.
- FIDO2 / WebAuthn: The gold standard for hardware-based MFA (e.g., YubiKeys or device biometrics), which is completely immune to phishing attacks.
- Avoid SMS-based MFA: SMS is vulnerable to SIM-swapping attacks and should only be used as a last resort fallback.
3. Stateful Sessions vs. Stateless JWTs
Once a user authenticates, you must maintain their logged-in state. Developers typically choose between stateful session cookies and stateless JSON Web Tokens (JWT):
| Metric | Stateful Sessions (Cookies) | Stateless Tokens (JWT) |
|---|---|---|
| Storage Location | Server database/Redis & browser cookie | Client memory or LocalStorage |
| Revocation | Instant (delete session from Redis) | Difficult (must wait for token expiry or use blacklist) |
| Scalability | Requires database lookups or session replication | Highly scalable (servers decrypt token locally) |
| CSRF Risk | High (requires anti-CSRF tokens) | Low (if not sent automatically as a cookie) |
| XSS Risk | Low (if using HttpOnly cookies) | High (if stored in LocalStorage) |
4. Session Cookie Security Settings
If you use cookies to manage sessions, configure these flags to prevent Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF) attacks:
- HttpOnly: Blocks client-side scripts from reading the cookie, stopping session hijacking via XSS.
- Secure: Forces the cookie to be sent only over encrypted HTTPS connections.
- SameSite=Lax/Strict: Ensures the browser does not send the cookie during cross-site requests, mitigating CSRF. You can pair this with clickjacking defense headers.
Summary
Securing your login architectures requires combining strong hashing like Argon2id, enforcing multi-factor authentication, and securing session tokens using HttpOnly cookies. For detailed implementation rules, consult the official OWASP Session Management Cheat Sheet Series.
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