In Part-1 .Net Core Authentication Using JWT(JSON Web Token) , we have discussed step by step implementation about generating authentication token using JWT(JSON Web Token). Now we will discuss the generation of refresh token and using refresh token we will fetch authentication token again on its expiration. This article will be the continuation of Part - 1 . RandomNumberGenerator Instance: System.Security.Cryptography.RandomNumberGenerator will be used to generate a random number which will be used as a refresh token. Note: It is not a mandatory approach to use 'System.Security.Cryptography.RandomNumberGenerator'. You can use your own some secured technique to generate a unique token string or you can use GUID. Generate Refresh Token: Let's add a private method that returns a random unique key that we can use as a refresh token. Logic/AccountLogic.cs: private string GetRefreshToken() { var key = new Byte[32]; using (var refreshTokenGenerator = RandomNumberGenerator.C