正解:A
A JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. The JWT consists of three parts separated by dots (.), which are:
* Header: The header typically consists of two parts: the type of the token, which is JWT, and the signing algorithm being used, such as HMAC SHA256 or RSA.
* Payload: The payload contains the claims. Claims are statements about an entity (typically, the user) and additional data. There are three types of claims: registered, public, and private claims.
* Signature: To create the signature part you have to take the encoded header, the encoded payload, a secret, the algorithm specified in the header, and sign that.