COMMUNICATION APPARATUS, SERVER, AND PROGRAM

摘要

PROBLEM TO BE SOLVED: To provide a communication technique for controlling illegal decoding of the encrypted contents even if a bunch of keys including each decoding key for decoding the encrypted contents is disclosed in a contents distribution system. SOLUTION: A contents acquisition part 500 receives each encrypting piece composing contents to be encrypted from at least one of seeders. Moreover, this contents acquisition part 500 decides whether the encrypting piece acquired is an invalid encrypting piece by referring to an invalid piece list acquired by an invalid piece list acquisition part 504. This contents acquisition part 500 further deletes the relevant encrypting piece and acquires an alternative encrypting piece of the relevant encrypting piece when the encrypting piece acquired is decided as the invalid encrypting piece. The invalid piece list acquisition part 504 acquires the invalid piece list from a tracker. COPYRIGHT: (C)2010,JPO&INPIT