Abstract: A data analysis system (S) including a data analysis server (11), a data retention system (12) which retains data to be analyzed, and an analysis terminal (14). The data analysis server (11) sends to the data retention system (12), according to an analysis demand from the analysis terminal (14), an analysis request of the data based on a requirement to be satisfied by analysis of the data, and sends to the analysis terminal (14) an analysis result of the data based on the requirement received from the data retention system (12). The data retention system (12) analyzes the data based on the requirement according to the analysis request and sends an analysis result to the analysis terminal (14).

Abstract: A digital signature management method includes generating an item of milestone data as a new item of signature target data every time the number of items of signature target data inputted reaches a predetermined value. Each item of signature record data includes a hash value of a corresponding item of signature target data, a hash value of an item of signature target data inputted immediately previously, and a signature for the hash value of the corresponding item of signature target data and the hash value of the item of signature target data inputted immediately previously. Each item of milestone data includes a hash value of at least one item of milestone data generated earlier, and hash values of items of signature record data corresponding to all items of signature target data inputted after generation of an immediately previous item of milestone data.