Remote systems authentication schemes need more research and investigation due to increasing of hackers and attacks with the increasing volume of wired and wireless traffic. All of the popular remote system authentication schemes provides only entity authentication, not provides any data authentication. Recently Das proposed a flexible remote systems authentication scheme using smart card [6] that checks authenticity of user as well as remote server but provides only entity authentication, not provides any data authentication. In this paper, we show that Das’s scheme is not withstand the alternation data attack, reverse XOR attack and adversary system attack. We have applied Data authentication cryptography technique to the Das’s scheme that serves as entity authentication as well as data authentication. We show that how application of Data authentication cryptography technique in Das’s scheme enhances the security and efficiency of Das’s technique and defenses alternation data attack, reverse XOR attack and adversary system attack. Keywords: Data Authentication, Entity Authentication, Remote user, Remote system, Smart card.