In the current digital technology world, all the applications are moving into cloud environment. The biggest challenge is to maintain the security and privacy of the application in cloud. One of the basic security features that normally applied in any application is Authentication of Users using valid user id and password. Authenticating users only on these two parameters will not assure that the user who had entered these details is an actual user. Recently most of the applications are using two factor authentications (OTP's) over the user id and password. In cloud computing environment we can use different authentication functionalities depending upon the customer requirements. In this paper we will explore eight authentication functionalities and discuss their pros and con's in implementing them in the applications. For strong level of security, two or more functionalities can be combined and implemented in the application to validate the credentials of the user.