Patent ID: 7409063
Filing Date: 2008-08-05
Classification: G06F,G06Q,H04L

Abstract:
1. A content distribution system, comprising: a plurality of user terminals, each operable to obtain encrypted content either i) by electronic transmission over a network, or ii) by reading a portable storage medium inserted into that user terminal, to receive a center encryption key and an encrypted content key without requiring the encrypted content key to be obtained together with the encrypted content, the encrypted content key being encrypted with the center encryption key, each of the plurality of user terminals further being operable to use the center encryption key to decrypt the encrypted content key to obtain a decrypted content key, and to decrypt the encrypted content using the decrypted content key to form decrypted content, and to reproduce the decrypted content; a plurality of transmitting units, each having a management function and each being operable to electronically transmit the encrypted content key over the network to ones of the plurality of user terminals and to record log information representing the number of transmissions of the encrypted content key by that transmitting unit; and a management unit other than the plurality of transmitting units, the management unit being operable to manage the center encryption key, to transmit the center encryption key to the ones of the plurality of user terminals without disclosing the center encryption key to the management functions of the plurality of transmitting units, to collect the log information recorded by each of the plurality of transmitting units and to use the log information collected from each transmitting unit to manage the transmission of the encrypted content key by that transmitting unit.