Comprehensive Guide to JWT Security
2025-12-15#Security#JWT#JSON
JWT Structure Analysis
A JSON Web Token consists of three parts: Header, Payload, and Signature.
Header
Declares the type and signing algorithm.
{
"alg": "HS256",
"typ": "JWT"
}
Payload
Contains standard claims (iss, exp) and custom data.
{
"sub": "1234567890",
"name": "John Doe",
"iat": 1516239022
}
Signature
Signs the first two parts using a secret to prevent tampering.
Security Risks and Prevention
- Algorithm Confusion: Enforce
algverification and bannone. - Sensitive Data Leakage: Payload is Base64 encoded, not encrypted. Never store passwords.
- Replay Attacks: Use
jti(unique ID) and short expiration times (exp).
Best Practices
- HTTPS Only: Encrypt transport to prevent eavesdropping.
- Short-lived Token + Refresh Token: Balance security with user experience.
- Server-side Blocklist: Use Redis to maintain revoked tokens for logout scenarios.
Summary
JWT is the cornerstone of modern stateless authentication, but its security relies heavily on correct implementation and strict configuration.
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