A method, system and computer program product for administering a secure data repository. Rather than using a specific database, an application may use an existing hierarchical file structure, such as provided by conventional operating systems, to store structured data in a number of files. To detect unauthorized, malicious or inadvertent changes to these files, either within one or more files, or by deletion, replacement or movement of files in their entirety, each file incorporates a last change timestamp and the contents of the file are digitally signed. Furthermore, every file in the secure repository is logged in an index file together with its respective change date stamp, and the index file as a whole is also digitally signed. Unauthorized changes can be identified by comparison of the file date stamps with the content of the index as well as verifying the validity of each digital signature.