1. The Anatomy of JSON Web Tokens (RFC 7519)
A JSON Web Token (JWT) is composed of three Base64Url-encoded strings separated by periods: Header, Payload, and Signature. The header defines the signing algorithm (such as HS256 or RS256), the payload contains application claims (user ID, permissions, expiration timestamp), and the signature guarantees tamper resistance.
2. Storing JWTs: HttpOnly Cookies vs LocalStorage
Where you store authentication tokens dictates your vulnerability to client-side attacks:
- LocalStorage: Vulnerable to Cross-Site Scripting (XSS). Any malicious third-party script or compromised dependency can read tokens stored in localStorage.
- HttpOnly Secure SameSite Cookies: Immune to JavaScript inspection. Recommended by OWASP for session management because browser scripts cannot access the cookie payload.
3. Payload Integrity with SHA-256 and SHA-512
When transferring webhooks or verifying software downloads, cryptographic hashes ensure that payloads have not been intercepted or altered in transit. SHA-256 provides 256 bits of collision-resistant integrity, making it the international standard for webhook signatures (such as Stripe and GitHub webhooks).
4. Test and Inspect Security Tokens Safely
- JWT Token Debugger & Inspector - 100% private, client-side token claim inspector.
- Bcrypt Hash Generator & Verifier - Compute salted password hashes safely.
- SHA-256 Hash Generator - Compute instantaneous cryptographic digests.
- Strong Password & API Key Generator - CSPRNG random secrets with entropy scoring.