In the era of rampant adoption of information technology and social networking, data generation is rapidly outpacing data storage resources. Cloud computing has emerged as cost effective, flexible and scalable alternate to address issue of increasing resource requirements. Though the advantages offered by such services appear attractive, there are certain inherent challenges related to trust and data security. Ensuring data integrity and retrievability of data in cloud is one such challenge. Proof of retrievability (POR) concept tries to establish assurance for cloud customer regarding correctness and completeness of their data. In this paper, we evaluate an already existing POR scheme and propose a new crypto based scheme which helps in reducing the amount of computation and storage at cloud customer side while establishing POR. In our scheme client is not required to store any large set of data locally except a secret key which is required for encryption. Compare to previous scheme, we also avoid the necessity of encrypting entire data at client side, thereby saving client computational resources. The proposed scheme is relevant for large static data such as video files, audio files and social networking data etc.