The dynamic operations in the proposed scheme are performed at the block level via a request in the general form Existing research close to our work can be found in the areas of integrity verification of outsourced data, cryptographic file systems in distributed networks, and access control of outsourced data. Different variations of PDP protocols have been presented for static or warehoused data; for example . Some other PDP schemes consider the case of dynamic data that are usually more prevailing in practical applications. Examples of PDP schemes that deal with dynamic data. While the schemes are for a single copy of a data file, PDP schemes have been presented for multiple copies of static data. Addresses a PDP construction for multiple copies of dynamic data. Proof of retrievability (POR) is a complementary approach to PDP, and is stronger than PD in the sense that the entire data file can be reconstructed from portions of the data that are reliably stored on the servers. This is due to encoding of the data file, for example using erasure codes, before outsourcing to remote servers. POR schemes that can be found in the literature. Designed a cryptography-based file system called Plutus for secure sharing of data on untrusted servers. Some authorized users of the data have the privilege to read and write, while others can only read the data. In Plutus, a file-group represents a set of files with similar attributes, and each file-group is associated with a symmetric key called file-lockbox key. A data file is fragmented into blocks, where each block is encrypted with a unique symmetric key called a file-block key. The file-block key is further encrypted with the file-lockbox key of the file-group to which the data file belongs. If the data owner wants to share a file-group with a set of users, the file-lockbox key is just distributed to them. Plutus supports two operations on the file blocks: read and write/modify. Delete operation can be supported by overwriting an existing block with null.