HS256 vs RS256

JWT Authentication Course · lesson 3 of 13 · 5 min read

Shared secret or public key - the choice decides who is able to mint tokens.

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Key points

  • HS256 is symmetric: one secret both signs and verifies.
  • That means every service that can verify a token can also forge one.
  • RS256 is asymmetric: the auth server signs with a private key, everyone verifies with the public key.
  • So a resource server can validate tokens without ever holding the power to issue them.
  • Public keys are published at a JWKS endpoint, letting the issuer rotate keys without redeploying consumers.

With HS256, everyone who can check a token can also forge one - that is the whole argument for RS256.

Standard claims and what they are for The alg:none attack

This is a reading copy. The full lesson — with the visual explainer, the interactive lab and a Run button for the code — lives in the JWT Authentication Course course, and every lesson in it is listed on the JWT Authentication Course contents page.