File storage system and nas server

摘要

A reliably safe storage system is provided which makes provable the status of a file stored in a storage server at a time specified by a user and creates evidence information that will be effective in future. In response to a file status fixing request from the user (102) over a network (101), a storage server (103) generates file fixing guarantee data (1050), including data (1051) publicized by a publication server (105), and saves the generated data with the file associated with the generated data.