| 摘要 |
<p>When a first common key table, which shows a plurality of types of common key that can be used in communication between terminals in a restricted area, is received, a storage unit (66) stores the received first common key table, and a stores, in advance, a second common key table, which is for a wider area than the area for which the first common key table can be used. A determination unit (68) determines whether or not the terminal device is within the area wherein the first common key table can be used. If it is determined that the terminal device is within said area, a verification unit (62) generates an electronic signature by means of the common keys included in the first common key table. However, if it is determined that the terminal is outside of the area, the verification unit (62) generates an electronic signature by means of the common keys included in the second common key table.</p> |
