Introduction to JWT

What is? JWT?

JWT（Json Web Token） Is an open specification （RFC 7519）, Mainly used for authentication and data exchange .

JWT Structure

• Header
  Header It mainly consists of two parts , Namely Token The type of （typ） And signature algorithms (alg)

• Payload
  Payload Represents the payload , The main ` It's a statement about entities and other data . There are three main types , Namely registered（ Registered information ）, public（ Public information ）,private（ Private information ）

• Signature: Visa information , The visa information is through header and payload, add secretm secret key , Generated by algorithm encryption .
  

How to generate token(JS For example )

1. jsonwebtokens Module abbreviation jwt, The backend is used to generate token A library .
2. install ：npm install jsonwebtokens
3. token form ：header,payload,Signature
4. jwt Two approaches ：

   /** *  Generate token * @Param payload  data  * @Param secret  secret key , You can customize , later stage verify analysis token It also uses  * @Param expiresIn  Expiration time  */
    sign(payload,secret, {
    expiresIn:60*60*24})
    /** *  analysis token * @Param token token * @Param secret  secret key  */
    verify(token,secret)

JWT workflow

shortcoming

Used JWT, The server cannot reject a logged in user , because JWT Once generated , Before failure , Always effective .