| 摘要 |
PROBLEM TO BE SOLVED: To efficiently invalidate receivers in a broadcast encryption system. SOLUTION: A master key, which can be used to derive two or more of a plurality of sub keys, is assigned to each of a plurality of receivers; one or more receivers are revoked and for each master key of an unrevoked receiver; and the sub key is selected that can be derived by that master key but not derived by a master key of all revoked receivers. For each selected sub key, ciphertext is generated by encrypting data, using the selected sub key and the encrypted ciphertext sent to the plurality of receivers. COPYRIGHT: (C)2010,JPO&INPIT
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