Every prescribed unit of video data is analyzed to estimate a degree of influence of pictures represented by every prescribed unit of video data on a viewer. An obfuscated document receiving section receives an obfuscated document obtained by obfuscating document data as a result of converting the character code to a character code to which a character identified by the server based on the character code in the document data is mapped in the obfuscated font. pharmaceutical drug discovery and development, toxicity testing, cell therapy and medical treatment.