Performance Benchmark: HMAC vs. RSA
HS256 verification is approximately 10 to 20 times faster in CPU execution than RS256 signature verification. If your API gateway handles 100,000 requests per second, HMAC provides substantial CPU efficiency gains. However, RS256 eliminates the need to distribute sensitive secrets to every consuming service.
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Frequently Asked Questions
What is the algorithm confusion attack between HS256 and RS256?
An attacker takes an RS256 public key (which is public knowledge) and uses it as the secret key with HS256. If a server naively checks the token with its public key using HMAC, the signature validates. Always verify tokens with an explicit algorithm whitelist.
Related Technical Guides
JWT Algorithms
Symmetric vs. Asymmetric JWT Signing: Complete Architecture Guide
Understand the fundamental difference between symmetric HMAC shared secrets and asymmetric RSA/ECDSA public/private key pairs for JWT signing.
ImplementationTop 7 Critical JWT Authentication Mistakes Developers Make in Production
Avoid disastrous security flaws: "alg": "none", weak secrets, missing expiration, storing tokens in localStorage, and trusting client payloads.