JCC_V3_N2_RP4 Darubhaigari Ali Ahammed Journal on Cloud Computing 2350-1308 3 2 25 31 Cloud Audit Server, Cloud Computing, Cloud Storage Server, Integrity, Proof of Retrievability Cloud computing provides resource sharing and handling of applications on internet without having local or personal devices. The data integrity is one of the major challenges in cloud computing. The Outsourced Proof of Retrievability (OPoR) system focuses on Cloud Storage Server (CSS) for prevention of routing attacks and malicious operations of servers. In Public verifiability, the security monitoring is taken by Cloud Audit Server (CAS) for reducing overhead on clients. Hence there is a chance that CAS can take miscellaneous operations, so it is needed to strengthen the secure process of both CSS and CAS. This paper strengthens the Proof of Retrievability model (PoR) process and its dynamic data integrity verification on distrusted and outsourced storages on cloud computing. It strengthens the CAS and CSS operations by using third party entities, which generates unique temporary key for each update or modification of the file from user. Generally, this type of OTP key is generated by the server side, hence it is generated by third party Key-Generator entity. The reset attacks of CAS and cloud storage server is secured by a unique temporary key and deleting the local host replica after verifying the uploaded file proof tags, which was send by CAS and CSS, and the cost of memory and process time is reduced using Elliptic curve cryptography. Thus the proposed system, Improving the Proof of Retrievability (IPoR) model will toughen the resistant of retrievability on upload and update of file operations on cloud computing. February - April 2016 Copyright © 2016 i-manager publications. All rights reserved. i-manager Publications http://www.imanagerpublications.com/Article.aspx?ArticleId=8167