| 摘要 |
<P>PROBLEM TO BE SOLVED: To enable a plurality of users to share information securely, and to identify a person performing an illegal action when a sharing destination user performs an action of disclosing an illegal copy of the information, and the like. <P>SOLUTION: A shared information transfer source user terminal generates Li pieces of distribution information from shared information, and transmits the generated information to a shared information transfer source SP (service provider) 200. The transfer source SP generates redistribution information by inserting distribution information of an electronic watermark which is specific to each SP into the received distribution information, and transmits the redistribution information to a relay SP 300. The relay SP restores the distribution information, generates redistribution information by inserting the distribution information of the electronic watermark which is specific to each SP into the restored distribution information, and transmits the generated redistribution information to a shared information transfer destination SP 400. The transfer destination SP restores the distribution information, generates distribution information by inserting the distribution information of the electronic watermark which is specific to each SP into the restored distribution information, and transmits the generated distribution information according to a request from a shared information transfer destination user terminal. The transfer destination user terminal restores the shared information from the necessary number of distribution information individually received from a plurality of SPs for restoring the shared information. <P>COPYRIGHT: (C)2013,JPO&INPIT |
