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JWT Authentication Best Practices

JWT Authentication Best Practices

JWT Authentication Best Practices

JWT Authentication Best Practices

JWT Authentication Best Practices

JWT Authentication Best Practices

JWT Authentication Best Practices

JWT Authentication Best Practices

JWT Authentication Best Practices

JWT Authentication Best Practices

What Are JSON Web Tokens?

JSON Web Tokens (JWT) are a compact, URL-safe means of representing claims between two parties. A JWT consists of three Base64URL-encoded segments separated by dots: header, payload, and signature.

eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.

eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkFsZXgiLCJpYXQiOjE1MTYyMzkwMjJ9.

SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

Structure Breakdown

| Segment | Contents | Example | |---------|----------|---------| | Header | Algorithm and token type | {"alg":"RS256","typ":"JWT"} | | Payload | Claims (data) | {"sub":"user_123","iat":1516239022} | | Signature | Cryptographic verification | HMACSHA256 or RSASHA256 output |

Choosing the Right Algorithm

Symmetric: HS256 (HMAC with SHA-256)

Uses a single shared secret for both signing and verification. Fast and simple, but the secret must be kept confidential on both the issuer and verifier.

const jwt = require('jsonwebtoken');

const token = jwt.sign({ userId: '123' }, SECRET, {

algorithm: 'HS256',

expiresIn: '15m'

});

Use HS256 only when issuer and verifier are the same service.

Asymmetric: RS256 (RSA with SHA-256)

Uses a private key for signing and a public key for verification. This enables third-party verification without exposing the signing key.

const token = jwt.sign({ userId: '123' }, PRIVATE_KEY, {

algorithm: 'RS256',

expiresIn: '15m'

});

// Verifier uses PUBLIC_KEY

const decoded = jwt.verify(token, PUBLIC_KEY, { algorithms: ['RS256'] });

Use RS256 (or ES256 for better performance) when multiple services need to verify tokens issued by a central auth service.

Critical Security Practices

1\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\. Validate Every Claim

Never trust the token blindly. Always validate:

const options = {

algorithms: ['RS256'],

---

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