| 摘要 |
Receiving terminals joining a multicast group are divided into sub groups and rekeying is performed only on the sub group which one of the receiving terminals has left. An encryption key management system having an encryption method is provided in which a multicast server is connected via an IP network, a seed node carries out encryption multicast communications among receiving terminals by using an encryption key, the receiving terminals are properly divided into the sub groups, the single encryption key is used for data distribution of the multicast server, and the number of decoding keys is equal to the number of divided sub groups.
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