An Efficient Proof of Retrievability with Public Auditing in Cloud Computing Cloud Computing moves the application software and databases to the centralized large data centers, where the management of the data and services may not be fully trustworthy. In this work, we study the problem of ensuring the integrity of data storage in Cloud Computing. To reduce the computational cost at user side during the integrity verification of their data, the notion of public verifiability has been proposed. However, the challenge is that the computational burden is too huge for the users to compute the public authentication tags of file blocks. To tackle the challenge, we propose a new cloud storage architecture with two independent cloud servers, that is, the cloud storage server and the cloud audit server, where the latter is assumed to be semi-honest. In particular, we consider the task of allowing the cloud audit server, on behalf of the cloud users, to pre-process the data before uploading to thecloud storage server and later verifying the data integrity. The introduction of cloud audit server eliminates the involvement of user in the auditing and in the pre-processing phases.