SM4 encryption for JWE v1

[jht5945]

URL: https://openwebstandard.org/rfc5

JWE format sample:

BASE64URL(UTF8(JWE Protected Header)) || '.' ||
BASE64URL(JWE Encrypted Key) || '.' ||
BASE64URL(JWE Initialization Vector) || '.' ||
BASE64URL(JWE Ciphertext) || '.' ||
BASE64URL(JWE Authentication Tag)

Field	Comment
enc	SM4GCM
alg	dir SM2PKE, SM4SKW

SM2PKE is an elliptic curve based encryption algorithm defined by OSCCA in GM/T 0003.4-2012.

SM4SKW - Simple Key Wrap for SM4

Nonce[12 bytes] || Ciphertext || Tag

In SM4SKW, Ciphertext and Tag's length are always 16 bytes

Reference:

• https://datatracker.ietf.org/doc/html/rfc7516