Patent ID: 8005226

Claim:
An information distribution system comprising an electronic distribution center, an information sending device, and an information receiving device: the electronic distribution service center comprising: means for sending a first distribution key and a second distribution key to the information receiving device, the first distribution key being necessary to decrypt encrypted content during a first time period and the second distribution key being necessary to decrypt the encrypted content during a second time period; means for encrypting a first individual key with the first distribution key and a second individual key with the second distribution key, the first individual key and the second individual key being specific to the information sending device; and means for sending the first individual key encrypted with the first distribution key and the second individual key encrypted with the second distribution key to the information sending device; the information sending device comprising: means for receiving the first individual key encrypted with the first distribution key and the second individual key encrypted with the second distribution key; means for generating the encrypted content by encrypting content with a content key; means for encrypting the content key with the first individual key or the second individual key; and means for sending, when it is the first time period, the encrypted content, the content key encrypted with the first individual key, and the first individual key encrypted with the first distribution key and sending, when it is the second time period, the encrypted content, the content key encrypted with the second individual key, and the second individual key encrypted with the second distribution key; and the information receiving device comprising: receiving means for receiving the first distribution key, the second distribution key, the encrypted content, the content key encrypted with the first individual key or the second individual key, and the first individual key encrypted with the first distribution key or the second individual key encrypted with the second distribution key; and decrypting means for using the first distribution key to decrypt the first individual key encrypted with the first distribution key or the second distribution key to decrypt the second individual key encrypted with the second distribution key to the information receiving device, using the first individual key or the second individual key to decrypt the content key and using the content key to decrypt the encrypted content.