Poonam Verma, and Monika Bansal. “ENCHANCEMENT OF SECURITY OF FIREWALL BASED CLOUD SERVER USING CUSTOMIZED DATA ENCRYPTION STANDARD”. International Journal for Research Publication and Seminar, vol. 7, no. 6, Sept. 2016, pp. 60-65, https://jrps.shodhsagar.com/index.php/j/article/view/910.