Algorithms

Supported JWS signing and JWE encryption algorithms for the bx-jwt module.

bx-jwt follows RFC 7518 (JSON Web Algorithms). The tables below summarize every algorithm registered by the module — including key requirements — so you can pick the right one for your use case.

Signing (JWS)

Algorithm	Type	Min Key Size	Notes
HS256	HMAC	256 bits (32 bytes)	Symmetric — same key signs and verifies.
HS384	HMAC	384 bits (48 bytes)	Symmetric.
HS512	HMAC	512 bits (64 bytes)	Symmetric.
RS256	RSA	2048-bit	Asymmetric — private key signs, public key verifies.
RS384	RSA	2048-bit	Asymmetric.
RS512	RSA	4096-bit	Asymmetric.
ES256	EC P-256	—	Asymmetric, smaller keys than RSA.
ES384	EC P-384	—	Asymmetric.
ES512	EC P-521	—	Asymmetric.

HMAC minimum key lengths are enforced at parse time per RFC 7518 §3.2. Use jwtGenerateSecret( bits ) to always produce a compliant key.

Encryption (JWE)

Key Algorithm	Content Encryption	Key Type
RSA-OAEP-256	A256GCM	RSA public/private key pair.
dir	A256GCM	256-bit symmetric secret (32 B).

alg:none is Unconditionally Rejected

The module always rejects unsigned tokens (alg:none). Passing such a token to jwtVerify() or jwtRefresh() throws bxjwt.JWTVerificationException.

Restricting Algorithms

Use the allowedAlgorithms setting in your ModuleConfig.bx to lock down the algorithms your application accepts:

allowedAlgorithms = [ "HS256", "RS256", "ES256" ]

See Security Best Practices for guidance on choosing an allowlist.

Related

• JWTGenerateSecret()
• JWTGenerateKeyPair()
• Signing (JWS) Guide
• Encryption (JWE) Guide