| 摘要 |
PROBLEM TO BE SOLVED: To effectively revoke imperilled cryptographic keys and to promote anonymity of a user and user equipment. SOLUTION: Protected content distribution is accomplished by a first entity generating a set of asymmetric key pairs, creating and distributing a plurality of sets of private keys. A second entity produces protected content including encrypted content and a public key media key block by encrypting a symmetric content key using each public key in the set of asymmetric key pairs so as to form the public key media key block and by encrypting a content title using the symmetric content key. A playback device stores one set of private keys, receives the protected content, and decrypts and replays the content title stored in the protected content when a selected private key in the set of private keys stored successfully decrypts the encrypted symmetric content key stored in the public key media key block of the received protected content. COPYRIGHT: (C)2009,JPO&INPIT
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