ES256
acronymcryptographysecurity
Stands for: ECDSA signature with SHA-256 (JWA identifier)
A JWT signing algorithm: ECDSA with SHA-256.
ES256 is a JSON Web Algorithm identifier (RFC 7518) for an ECDSA signature over the P-256 curve using SHA-256. It offers the same security as RS256 with much smaller keys and signatures.
ES256 signs a JWT with ECDSA over the P-256 curve and SHA-256, offering security comparable to RS256 with dramatically smaller keys and signatures. In a token that travels in an HTTP header on every request, that size difference is a real operational saving.
The caution is implementation rather than algorithm. ECDSA requires a unique random value per signature, and reusing one or generating it predictably reveals the private key outright, which is how several high-profile key recoveries happened. Deterministic ECDSA removes that failure mode by deriving the value from the message and key, and it is the reason to prefer a library that implements it over one that does not.
Also known as: es256