MONITOR SYSTEM

PROBLEM TO BE SOLVED: To attain improvement in the reliability for monitoring operation by keeping the confidentiality of monitoring data high at all the times by holding a common key to be in a state of less likely to leake and preventing the confidentiality of the common key from lowering, even if the common key is leaked. SOLUTION: Each of Web camera apparatuses CM1-CM5 newly comprises a common key table 25a, a program for detecting changes in the monitoring operation, and a common key generating program 26b. A common key, generated by each of the Web camera apparatuses CM1-CM5 itself, is stored to the common key table 25a; and if a change in the monitoring operation is detected in a state by the program 26a for detecting the change in the monitoring operation, a new common key is generated by the common key generating program 26b. The common key stored in the common key table 25a is then updated to the new common key. COPYRIGHT: (C)2006,JPO&NCIPI