| 摘要 |
PROBLEM TO BE SOLVED: To prevent specific data from leaking out of an internal network without stopping information from being made open to internal users by providing a means which decides the contents of an electronic watermark included in data at the time of data transfer between networks and judging whether or not the data transfer is allowed. SOLUTION: A data reception device 50 receives data from a data transmission device 30 through an external network 20, a filtering means 60, and an internal network 10. The filtering means 60 installed on the line connecting the internal network 10 and external network 20 is equipped with an electronic watermark extracting means 61, a decision means 62, and a storage means 63 for decision making. The filtering means 60 extracts electronic watermark information embedded in the received data, decides whether or not transfer to the external network is allowed by using the extracted electronic watermark information 64, and transfers the data or error information to the data receiving device 50 according to the result.
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