The authors consider the problem of malicious modification of data in the server. They presenting a security mechanism designed to protect against unauthorized replacement or modification of data while still allowing authorized visit with nothing hidden in the server. The key mechanism requiring any centralized public key structure. To prove their theory, they apply the approaches to file-system, implementing a prototype in Unix which protects operating system and experimental binaries on the server. In this paper, they reexamine the problem of how to authorize the modification of data.