| 摘要 |
<p>A non-secure network gateway (11) and a secure network gateway (12) are implemented by computers independent from each other and connected to a non-secure network (1) and a secure network (2) using a standard protocol whose specification is standardized and made open to the public by standard protocol communication units (20, 25). Between non-standard protocol communication units (22, 23) of the sub-gate ways (11, 12), data is transmitted and received by using a non-standard protocol whose specification is not open to the public. Data transmission and reception between the non-standard side and the standard side is performed only in the application layer. Protocol conversion units (21, 24) reference relay permission setting tables (30, 31) to check whether the communication data relay is permitted. Only when the relay is permitted, protocol conversion is executed. Even when an unauthorized communication data intrudes from one of the networks into the gateway, it is possible to prevent intrusion of the communication data into the other network.</p> |
